Cloth Finishing: Woollen and Worsted (1927) by John Schofield

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CLOTH FINISHING: WOOLLEN AND WORSTED

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Telegrams: ‘‘ WHITELEY, HUDDERSFIELD.” Telephone Nos. 1597 and 1598.

WILLIAM WHITELEY & SONS, Ltd.

LOCKWOOD, HUDDERSFIELD.

Over 5,000 Now in Use

8 Ces Guy AED

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fp ae

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2° ‘3, ° 0, oie 0, I 205, 0:

° © 22000000922”

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Pratt’s Patent Return Steam Trap.

ATTS PATENT

¥ a SONS Lt? Be LocKkwot

Made in Four Sizes. For returning condensed steam to boiler from mill heating, drying stoves,

te ar Tas e ES ates ek tentering machines, wool dryers, &c.

” —_—

Satisfactory working guaranteed up to 160 lbs. Boiler Pressure (Special quotations for higher pressure). Full instructions for fixing are sent with every Trap.

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i

WM. WHITELEY & SONS, LTD., LOCKWOOD, HUDDERSFIELD.

66” Double Cutting Machine.

66” Triple Cutting Machine.

MULTIPLE CUTTING OR SHEARING MACHINES

For all classes of Textile Fabrics. With or without CANBY’S PATENT LIFTING MOTION.

Machines fitted with any kind of Bed and Whiteley’s Patent Cut Adjuster.

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iil

ESTABLISHED 1854.

WM. WHITELEY & SONS

LIMITED,

TEXTILE MACHINISTS,

LOCKWOOD, HUDDERSFIELD, England.

Telegrams : ‘“‘ Whiteley, Huddersfield.” Telephone Nos. 1597 & 1598.

Improved Self-Acting Mule.

THE MOST PERFECT AND EFFICIENT MMULE MADE FOR SPINNING ALL CLASSES OF WOOLLEN AND ANGOLA YARNS.

ee

ALSO MAKERS OF: TWISTING, WINDING and WARPING MACHINERY. TENTERING and DRYING MACHINES for all Classes of Fabrics. « STENTERING MACHINES with Clip or Pin Chains. DRYING MACHINES for Wool, Cotton, Rags, etc. COMPLETE CLOTH FINISHING PLANTS for Woollens and Worsteds. PLUSH and ARTIFICIAL SILK MACHINERY. CARPET and PILE FABRIC MACHINERY.

COMPLETE ANILINE BLACK PLANTS and MERCERISING MACHINERY.

PRATT’S PATENT RETURN STEAM TRAPS.

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WM. WHITELEY & SONS, LTD., LOCKWOOD, HUDDERSFIELD.

‘Continuous Rotary (Hydraulic) Pressing Machine

For the continuous pressing of Cloth in the open or full width, and is made with either single or double nip.

Steaming and Cool Air Exhausting Machine With HORIZONTAL PUMP.

The most successful Machine on the Market for ‘ obtaining PERMANENT or SPOTLESS Finish.

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HIGH GRADE

PRESS PAPERS

GLAZED OR HARD ROLLED FINISH,

For large or narrow Presses, and Pressing Machines.

FENCINGS. HOSIERY PRESS BOARDS. I

H. & J. W. WRIGHT LTD.

MORTON,

Nr. BINGLEY, Yorks.

Established 1803.

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vi

bh

Machinery for Dyeing and Finishing All Kinds of Textiles.

Rayon and Cotton Yarn Dyeing Machine.

Artificial Silk and Cotton Yarn Dyeing Machine.

A DYEHOUSE IN ONE MACHINE.

Saves Labour. Better Shades. Ask for Particulars.

(rite or Phone Hed 160] to day for our representative to call

OUR SERVICE WILL SATISFY YOU.

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vil

“4

CSA

SHEARING ses am === aH ets uo M A H I N 5 \ 7 eet WS i) ware S SSS for

CARPETS, RUGS, MATS, COTTON LINEN and JUTE FABRICS.

BRUSHING, SIZING, DRYING,

and

MEASURING MACHINERY for MOQUETTES,

Etc.

Four-Cylinder Shearing Machine.

COMPLETE PREPARING, DYEING & FINISHING PLANTS for WOOLLEN and WORSTED PIECE GOODS, PILE FABRICS, Etc.

Send for Catalogue.

ENCINE Bripce MACHINE Works HUDDERSFIELD-ENGLAND

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Vill

PRICE’S OLEINES

have led the way for over 70 years

Safe with lowest premiums for Insurance

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ii, so

PRICE’

CLOTH OILS OLEINES HEAVY MUNGO OILS 70% PALE WOOL OILS 50%

———— ++]

Price’s Patent Candle Company, Ltd.

BATTERSEA, LONDON, S.W.11. Manchester Office: 26, CANNON STREET. Telephone: CITY 1321. Telegrams: “ PALMITINE.”

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PRICE’S CLOTH OILS

RICE’S Patent Candle Company, Ltd., were the pioneers in the British Isles in the Development of the Stearin Candle Industry and its by-products.

From 1829 onwards they have manufactured these pro- ducts at Battersea, London, and later at Bromborough

Pool, Birkenhead.

In the middle of last century they were the first to introduce the use of Oleines into the Woollen Industry.

Their Experience in these matters has been Unique.

They have further been pioneers in Housing Welfare Schemes for their employees and in the provision of Technical Education within their works.

This Experience and Pro- gressive Spirit is at the

SERVICE of the Textile Industry.

Price’s Patent Candle Company, Ltd., BATTERSEA, LONDON.

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Telephone - 875 HIGHER BROUGHTON.

WILLIAM BIRCH (Engineers) Lid.

Milton Street Ironworks,

LOWER BROUCHTON, MANCHESTER,

ENGLAND.

PATENT MACHINERY

Dyers, Finishers, Woollen Manufacturers.

fe} ORIGINAL INVENTORS, PATENTEES & MAKERS OF Listing or Bagging Machines, 2 in. Stitch.

Cloth Handling & Conveying Machines

To open out Fabric from the Rope state.

Scroll Openers, Metallic Squeezers. Patent Twin-needle Overlapping-seam Sewing Machines.

Blanket Whipping and Fringing Machines,

etc., etc. [=]

W. BIRCH’S PATENT PIECE-END SEWING MACHINE.

SEWS ANY THICKNESS, WET OR DRY. To sew from }” to 3” stitch, or from }” to 1” stitch.

f=}

Established 1863. Telegraphic Address: “TOPAZ, MANCHESTER.”

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|. SCHOFIELD, 'B:Sc., J. C. SCHOFIELD, B.Sc. CHons.)

_. The authors of this work are prepared to act as CONSULTANTS in the Dyeing and Finishing departments of the wool industries and to offer expert service on the matters particularly dealt with in this

book.

They have had long and special—in some respects unique—experience which is at the disposal of firms in the industry in all questions relating to cloth finishing, e.g., machinery, lay-out of plant and works, technology of processes and materials, and in particular the subject of defects and damages.

As investigations on the spot are of much greater technical benefit than mere laboratory testing, the authors specialise in actual works operations and undertake practical examination and report on mill routines.

Foreign consultations by correspondence and, in exceptional cases, by personal visit.

Enquiries may be directed to: Messrs. J]. SCHOFIELD, Rose Cottage, Netherton, HUDDERSFIELD.

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TEXTILE PHILOSOPHY.

‘“*I dread the time when the lean years come, when the wheels are clogged with the weight of taxation, and enterprise checked by fierce competition ; and unremunerative trade and idle labour forcing down wages.”

Sir JAMES HINCHLIFFE, 1915.

have often heard it said that woollen manufacturing is an art. If this is so, it follows that the manufacturer is an artist and very often a variety artist at that.”

J. N. Top, C.B.E.

‘The man who can really research and invent has been so exploited by the unconscientious employer that he will have none of it; he will simply let his inventive capacity die out.” PROFESSOR ALDRED BARKER.

** Where there’s muck, there’s money.’’——MILL Gossip.

** Quacks secrete ; scientists publish.’’—ANon.

“Of the many important branches of the textile industry that which deals with the finishing of fabrics has received the least T. WOODHOUSE.

** Whoever sets himself to see things as they are will find himself one of a very small circle ; but it is only by this small circle resolutely doing its own work that adequate ideas will ever get current at all.” MATTHEW ARNOLD.

**A man should be fit for more than he is doing.” : GARFIELD.

“With no reverence for the past, and no fear for the future.”’ HENRY Forp.

‘“* Since the War there has been an increasing desire to get ‘ something for nothing’. . . . and to escape manual work. Our educational system is in great danger of justifying the condemnation ‘ water spilled on the ground which cannot be gathered up again.’ Hitherto not sufficient attention has been paid to the acquisition of scientific method.” Dr. T. OLIVER.

will have to be done about it some day.” MAN IN THE STREET.

““I know, among the many fatuities that have been uttered in the press and in the pulpit to excuse our educational failure, it has been held that if we had imitated the Germans in thoroughness and scope of education we might have been ‘as wicked as they were ’.”’

Str Harry JOHNSTON.

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ERRATA.

Page 8. Fig. 1. Replace ‘‘Lime-Soda”’ by “Permutit.”’

Page 386. Fig. 114. Replace ‘‘absorbtion” by

Page 405. Fig. 122. Replace ‘Principal’ by

CLOTH FINISHING: WOOLLEN & WORSTED.

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Copyright at Stationers’ Hall.

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CLOTH FINISHING: WOOLLEN & WORSTED.

BY

JOHN SCHOFIELD, B:Sc., A.R.C.Sc.,

FELLOW OF THE PHYSICAL SOCIETY,

AND

J. COLIN SCHOFIELD, B.Sc. (Hons.)

TECH. CERT. IN WOOL, COTTON, AND SILK DYEING, AND CLOTH FINISHING.

HUDDERSFIELD: NETHERWOOD, DALTON & Co., Ltp., BRADLEY MILLs. 1927.

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PREFACE.

HE present work has been developed from the author’s Scouring and Milling (1921) which was itself extended into The Wet Processes of the Wool Industries (1925). In the preparation of those works it became increasingly apparent that there were large gaps in the literature of ‘wool textiles and on the publication of the latter book it was pointed out that the field of Dry Finishing was similarly incompletely covered. A comprehensive textbook on cloth finishing—based on scientific principles but severely practical in intention—was badly needed in the industry.

The aims of the authors may be summed up as an en- deavour to treat subjects on which information has been previously lacking or inadequate and in particular to deal with Cloth Finishing as the practical application of chemical, physical and mechanical principles. From this point of view the book is largely pioneering and it is inevitable in breaking new ground that the results may be somewhat informal or even in slight degree, disordered. In the opinion of the authors the art of cloth finishing is not primarily a matter of fabric design but consists rather in the action of chemical reagents, the effects of heat and moisture, and the results of applying mechanical stress to the wool fibre. It would be easy to make a general charge of neglect against the industry in this matter, and in this aspect the present work is a reaction against the older tradition.

It may be questioned whether certain special subjects are properly included in a work on cloth finishing. The authors have found in their lecturing, managerial and con- sulting experience a great dearth of information on many of these special topics, e.g. electric driving ; in other cases, e.g. wool scouring, the matters are obviously part of the general theory ; in further instances, e.g. humidity theory, they are portions of hitherto unexplored technics.

The authors owe much to the kind help of many firms and friends; Mr. L. Ellis, as before, in the preparation of illustrations; Mr. Johnson in the section on electric power; Mr. B. Ellis on raising, and many others. In all cases the attempt has been made to make reference in the text.

They are well aware that there are imperfections and even some inaccuracies in this book, but they consider that it is more important in the wool industry to abandon inertia and repudiate secrecy than to aim for the present at a com- pletely logical and exact scheme of treatment.

J:

Netherton, J, CG: SCHOFIELD. Huddersfield:

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Chapter

di

If.

ITI.

IV.

ve

VII.

CONTENTS.

WATER AND STEAM FOR TEXTILE PURPOSES — an ih

Sources of water, impurities, hardness, softening processes, testing of water, filtration and storage. Properties of steam, boiler feeds and heat losses, fuel economies.

Woot AND CHEMICAL REAGENTS — we ae ee Bi

Action of acids and alkalies on wool, preparation of working solutions, theory of solutions, indicators in textile work ; carbonising, sulphuric acid and wool, tendering.

Ors AND Fats — a — on si es a

Chemistry of fats, spinning oils, the wool lubrication problem, wool creams, oiling and scouring, oiling for worsteds, woollens and low goods.

SoAPS AND OTHER DETERGENTS — ne os a ue

Chemistry of saponification, relative solubility and detergent power, soap making in the mill, discussion of textile soaps ; special detergents, fuller’s earth and water-glass, etc., solvents, sulphonated oils.

THEORY OF DETERGENT ACTION — one pe me

Principles of Colloid Chemistry, properties of solutions, surface tension, formation of foams, adsorption ; interfacial tension, wetting-out, diffusion, properties of films.

Soap SOLUTIONS — _ ~ ven ied oa ie iS

Constitution and detergent action; oil-water emulsions, hydration of soaps, strength of soap solutions, effect of alkali, evaluation of detergents, retention of soap or alkali in fabric.

PRACTICAL SCOURING — ~ ad oe mt A

Routines, machines, tests of cleanliness, standard scours ; textile dirt, scouring of raw wool by solvents, wool washing. Backwashing, yarn scouring, piece goods. Preparatory operations, perching, knotting, mending, piece defects at the perch. Crabbing, plant and methods. Discussion of scouring principles, loss of strength in cloths, hosiery scouring, washing down.

Page

ol

84

118

143

175

205

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Chapter VIII.

IX.

ad,

XII.

XITI.

XIV.

Contents.

MILLING ~ ~ ~ = ~ ~ a -

Objects of milling, theories of felting, structure of wool, factors of milling, influence on fabric strength, turgescence, milling routine, acid milling, mechanics of milling plant. Finishing routines, worsteds, woollens, and low goods.

MInor PROCESSES - oe se en si

Blowing ; condition, lustre, shrinking, pressure blowing, blowing plant. Shrinking; methods, chemical shrinking, unshrinkable flannels. Roll boiling or potting, dewing or damping, steaming. Water-proofing, chemistry of in- soluble soaps. Piece staining and burl dyeing.

Woot AND MOISTURE — ie ii ian - -=- ad

Regain, atmospheric humidity, condition in wool, theory of sorption of moisture by wool, states of water in wool, limits of sorption; mathematical laws of regain, time rates of regain, diffusion theory of regain, Schloesing and Hartshorne’s experiments. Setting properties of wool. Conditioning processes. Ventilation and humidification of works.

Tur Dryinc PROCESSES _ ~ an a os

Types of drying; hydro-extractor, theory, tests and efficiency. Vacuum drying, contact drying, drying by air currents. Drying of wool, yarns, and pieces. Tenter machine, heat balance sheet in tentering.

CHEMISTRY AND PHYSICS OF THE WooL FIBRE _ _

Protein chemistry, purification of wool, intrinsic colour of wool; the gelatin analogy. Statistics of the wool fibre, mechanical properties, autographic testing of fibres.

TEXTILE CLEANLINESS — ~ oe lie ae pi i.

Materials and design of machines, lay-out of plant. Corrosion in works. I

THE CuTrTinac PROCESS oe a bd

Objects of cutting; Cutting machines; Adjustments; Grinding; Fancy cutting.

Page 275

327

369

417

45]

487

499

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Contents.

Chapter Page XV. THE RAISING PROCESS _ — ~ ~ _ _ 527

Objects of raising; Teazle machine; Wire card machines ; Single and double action raising plant; Raising and cloth factors.

XVI. THE PRESSING PROCESS. - ~ ~ ~ - 579

Theory of pressing; Pressing plant; Electric heating ; Automatic handling.

XVII. FInisHINGc ROUTINES — ~~ on fae _ ~ 607

General discussion; Worsted finishes; Woollen finishes ; Finishing of hosiery.

XVIII. Derects, DAMAGES AND STAINS, ~ ~ _ —- 683 Appendix A. GLossary or TECHNICAL TERMS a) Rae ae BOG Appendix B. ENGLISH—GERMAN GLOSSARY -— ~ ~ we OFM

Appendix C. SELECTED QUESTIONS - ~ - ~ —- 719

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WATER AND STEAM IN THE SCOURING SHED.

>

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CHAPTER I.

Water and Steam in the Scouring Shed.

WATER

is the medium in which the scourer carries on his cleansing operations. It is even more essential, in locating the site of a finishing works, to secure an ample supply of good water than an easy access to fuel, or transport of goods. Steam may be generated from comparatively impure waters, and power may even be purchased, but no high-class finishing of textiles is possible with bad water. It is not intended here to enter into the familiar chemistry of water given in scores of text-books, nor into the geology of water sources ; the practical textile requirements will alone be discussed. The water supplies of textile works are usually derived from :— 1. Rain; a soft, non-turbid water. When collected from roofs the atmospheric dust may harden it considerably. 2. Springs and wells; usually clear but may be hard, depending on the strata from which they are derived. Boreholes are similar ; it is often possible to judge the character of the water from the geological section of the bore, almost without chemical examination. 3. Rivers and canals; generally containing suspended matters, sometimes oil-films, and often hard. In industrial districts they may contain sewage, alkaline sulphates from seak purification, colour from exhausted dye-baths, iron corrosion, etc. 4. Public supplies; these vary in hardness, sometimes naturally, often to treatment. They are generally filtered. The standard of all waters is, of course, the Distilled Water of the chemical laboratory. It is a common error to suppose that the condensed water—the drainage from the heating systems of factories—is practically a distilled water; in the writer’s experience such water is more often worthless than

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not, carrying quantities of iron corrosion and occasionally grease. In one consultation it was found that the hot-well catching this condensed water from radiators and heating pipes, was also directly supplemented from the local canal !

A classification of industrial waters on chemical grounds might also be made as follows :—

1. Waters of alkaline reaction due principally to the bicarbonates of lime or magnesia ; often also containing sulphates, chlorides and nitrates of calcium and magnesium, and possibly some silica or iron. Most waters useful in textile work come within this group, and softening to a greater or lesser degree may be necessary. 2. Waters, often of high alkalinity, containing bicarbonate of soda. These are comparatively rare, occurring usually as boreholes. They are easily made available for textile purposes. 3. Waters of acid reaction, in general vegetable or humus from peat areas, e.g., the typical high level sources in the West Riding textile districts. 4. Waters polluted from surface drainages, sewage, trade effluents, etc., as for example, many river and canal supplies. Such waters may require both filtration and softening prior to textile utilisation ; or alternatively, chemical precipitation.

The actual weight of mineral impurity in most water supplies is relatively small as compared with the water itself. Thus a water might contain total mineral constituents of say, 0.05 per cent. by weight pure water of 99.95 per cent., and yet show a hardness of approximately 20 degrees; an impossible water in the untreated state for textile applications. Generally, therefore the results of a water analysis are expressed in parts per 100,000 or in grains per gallon. (One gallon of water weighs 70,000 grains.) Thus a peaty water for a public supply might contain about six parts of mineral matter—sulphate and carbonate of lime, sulphate of magnesia, and chloride of sodium principally—giving a hardness of about three degrees. Rain-water contaminated by atmospheric dust only would have a very similar mineral composition, but if subject to sooty impurity in addition, the mineral residue might be many times greater. Sea water is approximately a three per cent. solution as regards common salt, containing about 2,100 grains per gallon ; other mineral salts may increase this to 2,500 or 2,700 grains per gallon.

Too much elaboration is as a rule expended by mill-owners upon the chemical analysis of water, and when obtained the result is apt to be regarded as good for all time. Most water

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supplies are variable, for reasons apart from accidental contaminations. It is generally sufficient, in investigating the causes of bad working in a dyeing and finishing plant, to test the water by a simplified analysis, such as the scheme below ; this will reveal anything of an exceptional or prejudicial character. In this scheme, comparative test-tube trials are made side-by-side with distilled water, in most cases with single drops of the reagents. 1. Acidity or Alkalinity ; test by litmus, phenol and methyl orange. Certain waters, e.g., drainage from peat moorland, are usually acid, and carbonic acid gas is a common constituent of most waters, holding the Calcium and Magnesium in solution as bicarbonates. Chlorides ; one drop of silver nitrate with a trace of nitric acid. 7 Sulphates ; barium chloride with a trace of hydrochloric acid. Iron; by potassium ferrocyanide or thiocyanate. Sulphur : as sulphides ; by the smell and by lead acetate.

and turbidity should also be examined. Such test- trials should be followed by a proper determination of the hardness, temporary and permanent, of the sample, and in general the Clark soap test will be sufficient for the purpose of textile applications. If, now, this approximate examination has brought to light exceptional features in the water, a full investigation may be made; but, in general, waters requiring this will not be found suitable—even with any practicable or economical treatment—for textile purposes.

NOTE ON INDICATORS FOR WATER TESTING.

Some discrimination must be used in the employment of indicators when testing waters for acidity or alkalinity. Thus carbonic acid disturbs the indications of phenol phthalein ; and bicarbonate of soda, which is a strongly alkaline salt neutralising strong acids, gives no change of colour with phenol phthalein. Methyl] Orange is unsuitable for the indicating of boiler waters, as it is affected by nitrites, which commonly occur in such waters. Methods of determining acidity and alkalinity in dilute solutions based upon ionic concentrations are now coming into general employment; such routines may be applied to the examination of water. (See later).

HARDNESS OF WATER.

Chemically speaking, this ordinarily means the amount. of calcium and magnesium salts—carbonates and sulphates—in a water; but as other compounds, iron, etc., are also capable of acting in a similar way, it is most practical to define it as *‘ Soap-destroying The chemical equations given in

oe 99 be

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the chapter on oils and soaps, show how relatively small is the proportion of alkali in the soap molecule ; oleic acid requires only one-seventh of its weight of caustic soda for the formation of soda soap. When, therefore, these soluble alkalies are replaced from hard waters by the alkaline-earth metals

Calcium and Magnesium, the destruction of soap is very great. SODIUM OLEATE, CALCIUM CARBONATE,

(C,,H; ,COONa) + Ca CO, = 2 x 304 100

LIME SOAP. CARB. DIOX. WATER. (C,,H,,COQ), Ca 4+ CO, + Ti Hence, 100 parts of Carbonate of Lime neutralise 608 parts of Sodium Oleate or hard soap, in forming insoluble lime soaps ; that is, every grain of Calcium Carbonate destroys six grains of soap. Now one degree of hardness is equivalent to one grain per gallon of carbonate of lime. Thus, 500 gallons of water, a not unusual amount for the washing off stage of a set of pieces in the rope-scourer—for every degree of hardness will render useless 6 x 500 or 3000 grains of soap, reckoned anhydrous. Taking 7000 grains to the pound avoirdupois and allowing for 30% water in the soap, it may therefore be said that 1000 gallons of water can destroy over 1 lb. of soap for every degree of hardness it possesses. Moreover, the pre- cipitation of the sticky insoluble lime soaps upon the cloth is ruinous to the bleaching, dyeing and finishing processes generally. Water is the most general of all solvents ; indeed this is the basis of its detergent applications. A summary of the solubilities of substances entering into scouring practice is given below; the numbers represent parts of substance

dissolved per 100 of water. PARTS PARTS DISSOLVED SUBSTANCE. ar 16° cut. aT 100° CENT. Pot. Carbonate 109 156 Sod. Carbonate 16.5 45 Sod. Chloride 35 39.5 Sod. Sulphate (10 aq.) 39.8 322 Sod. Hydrate 60 250 HARDNESS SALTS :— . Calcium Carbonate 0.002 0.09 Calcium Sulphate 0.24 (0°C.) 0.22 Magnesium Carbonate Insol. Insol. Magnesium Sulphate (7 aq.) 33.8 73.8 GASES :— —_—__—— Carbon Dioxide CO, 1.02 volumes at 15° Cent. Sulphur Dioxide SO, 47 = Ammonia NH, 785 oa #

Chlorine Cl 2.64

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WATER SOFTENING.

Water Hardness is in the main of two kinds :— 1. Temporary ; due to carbonates of lime and magnesia held in solution by carbonic acid gas, and therefore precipitable by boiling. 2. Permanent; due to the soluble sulphates of calcium and magnesium, or even the chlorides and nitrates of these metals. In boilers at the higher temperatures, the above distinction largely fails, and the scale deposition will contain the sulphate of lime as well as the two carbonates; corrosions by de- composition also occur, and iron rust is thrown down. The practical methods of softening waters fall into two sections :—

I. Treatments by :— 1. Lime only for purely temporary hardness. 2. Sodium carbonate or Caustic soda. 3. Lime and Soda, the commonest case.

II. The Permutit Process of percolation through an artificial zeolite. The usual hard water requires both lime and soda for the removal of the temporary and permanent hardness; a water may be brought down to 3-4°, Clark degrees, if regularly and efficiently worked, i.e., checked by soap test and adjusted accordingly. Most softening plants differ merely in the mechanical details adopted to add the active chemicals to the bulk-water, and the sedimentation or filtration of the pre- cipitates ; the chemical principles are generally the same for all types. The Permutit process is an interesting exception. An artificial silicate of the type :— oor At. 0; Na,O 6° HO is manufactured by fusion; the substitution of the soluble alkali in this by the calcium and magnesium of the hard waters constitutes the softening operation; this substitution is reversible, a treatment by 10% common salt solution during the night stoppage renovating the permutit mass. The reactions of the base-exchange methods of water soften- ing may be represented thus :— Na,O (Z) + CaSO, = CaO (Z) + Na,SO, where Z is the zeolithic compound. For the reversible change, CaO (Z) + 2Na Cl = Na,OZ + CaCl,, in which the cycle proceeds from left to right. The first exchange represents about 1-2 per cent. reckoned as CaO on the weight of zeolite; regeneration is effected by a 10 per cent. salt solution. Obviously the rate of flow through the plant must not be excessive, i.e., such softening plants cannot be forced. In a published case, 5000 gallons of water of 24 degrees hardness were softened by a bed of permutit containing 2000 lbs. weight, and regeneration was effected by

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a solution of 88 lbs. of common salt in 88 gallons of water, i.e., 10 per cent. concentration, about five hours being allowed for this phase. In view of the increasing importance of the artificial zeolites for the softening of industrial waters, some further information may be given. The peculiar action in this respect of certain natural aluminium—alkali silicates such as analcime had been noted as early as 1905 by Professor R. Ganz and it was followed

ee ee ae ae

I my ya ma I a|a Q I \ Hh) I I Hi |! i i I ti nt I i Qn- —, STEAM INLET een FE WATERY i T mrs Se Oe ‘oan |! I \ A, seen sate sete Nes a i Om ee I 1 I MeTeR jin HI Ht : : \ i I 8 dD} I I bod 0e010 iP Q ore TT <— I Oa || I : ! 1 {i 1 1th || ' I HARD _ 7 I ny ft I ATER) fy): ALTE iH vy I 1 ad { Le 3 SF Y CaS A ls D4 hs WH a WY Yiu S BQ y SY , F be.

REGCENERATING. x DRAIN VALVE |,

~- ec = _

t ‘ ‘ ~ et : ' ' ! a peg

ae at Ni” sila SB a gE Sd Wr] ™ 1.—LIME—SODA SOFTENING PLANT. (UnITED WaTER SorreNerRsS, Ltp., LONDON.) up by analysis. It was concluded that in the naturally active bodies the sodium is only indirectly combined with the silica

through the medium of the alumina. In the case of inactive products, e.g., natrolite, there is probably direct combination

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9

of alkali and silica. Melts of varying composition were then prepared from mixtures of kaolin, quartz, and soda carbonate, and crystalline zeolites obtained therefrom. The artificial zeolites are amorphous, opaque, glassy products, easily de- composed by dilute mineral acids. Organic acids and highly diluted inorganic acids react by dissolving first the soluble alkali and afterwards small proportions of the alumina and silica. The residual bodies termed ‘‘ Permutit ”’ acids revert on immersion in solutions of alkali carbonates to the original zeolith, the carbonate solution becoming bicarbonate; a tendency so marked that solutions of sodium chloride are broken up with the liberation of free hydrochloric acid. The principle of base-exchange thus introduced into the practice of water softening has been considerably developed.

Note.—An excellent review, from the textile standpoint, of the water softening position to-day, including the Permutit process, etc., will be found in the Journal of the Society of Dyers and Colourists, December, 1918, (p. 240); papers by Messrs. P. E. King and E. V. Chambers.

The chemical reactions occurring in the Lime-Soda system of softening are represented by the following equations, the lime employed being in the form of slaked or hydrated lime and the soda as carbonate :—

1. Temporary Hardness only ; due to Calcium Bicarbonate. CaH, (CO,), + Ca (OH,) = 2CaCO, + 2H,O 100 74 2. Temporary Hardness only ; due to Magnesia Bicarbonate MgH, (CO,), + 2Ca (OH), = 2CaCO, + Mg (OH), + 146 2x 74 2 ; the precipitate is jointly carbonate of lime and hydrate of magnesia. 3. Permanent Hardness; due to Lime Salts, e.g., CaSO, + Na,CO, = CaCO, + Na,SO, 136 106 4. Permanent hardness ; due to Magnesium Salts, e.g.,

MgSO, + Ca (OH), = Mg (OH), + CaSO, ; 120 74

the further addition of soda-ash bringing about re- action (3) above. 5. Presence of Free Carbonic Acid ; treated by lime.

CO, + Ca (OH), = CaCO, + H,O| 44 74

6. Caustic Soda softening processes, e.g., CaH, (CO,), + 2NaOH = CaCO, + Na,CO, + H,O. MgH, (CO,), + 4NaOH = Mg (OH), + 2NaCO, + 2H,O; and for permanent hardness MgSO, + 2NaOH = Mg (OH), + Na,SO,.

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10

Calculation from the theoretical equations is based upon the assumption that the hardness is due to calcium carbonate and hence 24 parts of magnesium or 40 parts of calcium present in any form are regarded as equivalent to 100 parts of CaCQg,. Equation (1) (p, 9) therefore shows that 74 parts of hydrate of lime will be required for 100 parts carbonate of lime or 0.74 grain per gallon per Clark degree of temporary hardness. Similarly, in equation (3), 136 parts of calcium sulphate which are represented by 100 parts of the standard hardness of CaCO,, require 106 parts of sodium carbonate ; and therefore 1.06 grains of sodium carbonate per gallon are necessary for each degree of permanent hardness. From these data the approximate quantities of softening reagents applicable in any particular case may be reckoned, when the hardness, temporary and permanent, has_ been determined and the volume of water required is known. In actual softening practice this procedure is subject to control. There may be free carbonic acid present in all degrees from fractional amounts to considerable aeration. The soap test for hardness—while probably the most useful in textile applica- tions—is not a complete indication of the properties of the water under examination, and is liable to serious errors in the more extreme cases. Under these circumstances softening plants are invariably put into operation by a more or less tentative series of trials, checked by soap or other tests and varied by addition or diminution of the active chemical reagents as indicated. It is obvious that there can be no universal system, either of particular reagents or of quantities thereof, applicable to all cases; each instance must be in- vestigated and treated on its own merits. A West Riding borehole averaging a little over 7 degrees of total hardness— temporary 24, permanent 4}—required approximately 0.6 lb. quicklime and 0.7 lb. soda ash per 1000 gallons for good softening ; in this case there was free carbonic acid. A bore- hole in the hosiery district of the Midlands having 6 degrees temporary, 14 of permanent hardness and no free carbon dioxide required 1.7 lbs. slaked lime and 0.9 lbs. soda ash per 1000 gallons. Taking current market prices for these materials, estimates may then be made of working costs for reagents. The definitions of “ hard” and “ soft ’’ waters must inevit- ably be subject to variation. For scouring purposes on textiles the limits need not be the same as for potable waters or for boiler feeds. A classification given in a work on chemical analysis describes waters below 6 as soft, above 12 as hard, the intermediate 6-12 as medium hardness. An American authority fixes a limit of softness at 6-7. The behaviour of waters of different degrees of hardness in textile scouring will be discussed later, but in general it stated that waters

Page 35

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Page 36

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Page 37

13

of 7 and upwards are unsuitable for scouring purposes and it is desirable to secure when possible a supply of not more than 3-4 degrees. I There are diverse opinions as to whether the softening of a water below 3-4° H. is economical or even desirable for textile purposes, and whether any difference of handle or finish is perceptibly gained in the fabric. In the solvent process, by the use of benzine, petrol, etc., it is not found desirable to extract all possible grease, as the fibre loses some softness at the extreme limit. But attention is directed in this respect to a possible protective action of the ordinary scouring bath with alkali mentioned above. A well-softened water usually reacts slightly alkaline, say, about 1-1.5 c.c. of N/10 acid. Ammonium Oxalate should produce only a slight turbidity. Iron is a fatal impurity in textile waters, whether for scouring, bleaching, or dyeing ; yet the ochreous waters of colliery districts, losing carbonic acid on exposure to the air, completely precipitate their dissolved iron ; the well-filtered water may test perfectly iron-free. It must not be assumed that in water testing a given number of degrees of hardness necessarily precipitates its chemical equivalent of lime or magnesia soap in the scouring bath as insoluble soaps on the fabric. Since the scour nearly always contains soda-ash and is, moreover, usually warm, a softening action proceeds along with the scouring. The point does not seem to have obtained much notice, but it would appear that most of the calcium and magnesium carbonates produced are not really precipitated, but are carried in the scouring emulsion, much in the same way as the mechanical dirt of the fabric, and do not the soap. It is hardly likely that these carbonates, not dissolved but merely suspended in the scour, chemically attack the soap, and it is therefore probable that the common practice of alkaline scouring acts protectively to some extent against the hardness of water. Many so-called lime soaps in fabrics are really grease or soap residua due to imperfect scouring, and will yield to simple extraction by Ether or other solvent. When this extracted matter—or hydrochloric acid extraction thereof and even of the fabric itself—is tested chemically for the alkaline earths, this pro- cedure often fails to reveal any lime or magnesia whatever. The assumption of the presence of lime soaps in fabrics should be judged along with the evidence of the scouring water ; many patches, streaks, and stains are put down to this source which are really due to residual grease or soap, contaminated with rubbed colour or flock from dirty machines, etc. The whole question of Water Hardness in the textile aspect, 1.€., viewed as soap destroying power, is exceedingly com- plicated, and it is probable that the Clark test, crude as it

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seems from the purely chemical standpoint, is in practice superior to the more exact Hehner determinations of alkalinity, etc. Richardson has stated (Jour. Soc. Dyers & Col., 1893, p. 194) that one molecule of calcium as chloride will destroy 2.8 molecules of soap as oleate, and one molecule of magnesium as sulphate would require 4.2 molecules of soap. These ratios change with the ratio of the saline constituents present in the water and the amount of dilution and temperature; the greater the proportion of magnesium sulphate to the soap with the same volume of water, the fewer is the number of soap molecules decomposed. Allen has also found that a water containing both lime and magnesia does not destroy as much soap as the same amounts of lime and magnesia would do separately. It must be remembered also that for high dilutions such substances as magnesium carbonate and silica are sensibly, and calcium carbonate quite appreciably soluble. By definition, a water of 10 degrees of hardness means a soap destroying power ten times that of a water of unit hard- ness or one degree, but in practice a water with 10 parts carbonate of lime per gallon causes much less destruction of soap than a water having one part per gallon, reckoned relatively. Soap destroying power and content of calcium carbonate are not directly proportional. In the operation of softening plants some regular control is essential, as all natural supplies are variable owing to changes in rainfall, saturation of the ground, etc. Even large public reservoirs may vary in hardness in different seasons and ordinary wells and boreholes are subject to greater changes. Water softening in textile works goes wrong most frequently through negligent working, often simple failure to keep the plant supplied with the reagents in adequate or proportionate amounts. Ample storage and as long a time factor as possible, especially in lime-soda treatments, are necessary; there is often some after-precipitation which may take place in the tanks, pipes, boilers, etc. One design of plant seeks to over- come these defects by carbonating the treated water by the CO, in flue gases; these, however, contain sulphurous acid also, and no information seems available as to the effect of this factor, at any rate from the textile point of view. Excess alkalinity is undesirable in dyeing operations, e.g., the acid bath, or on cotton with basic dyes. The filtering arrangements of a softening plant should be very perfect; no solid pre- cipitates or turbidity can be permitted to go forward. Lime- soda plants worked in advance of the Permutit treatment may upset the working of the latter by passing free lime forward, depositing calcium carbonate therein. Again, it has been stated that Sodium Sulphate, one by-product of the Permutit system, is partly dissociated at boiling temperatures ; the point needs attention for boiler feeding.

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It does not appear to be well recognised that sufficient time must be allowed for the complete reactions to be accomplished. Especially is this necessary for the elimination of that part of the permanent hardness due to magnesia. In certain con- tinuous plants there is insufficient time permitted—particularly when the plant is forced—for the due completion of the softening operations, and after-precipitation occurs in the delivery mains and storage tanks; imperfectly treated or partially filtered water is sent forward to the boilers or scouring machines. In the intermittent types of softening plant, two large tanks of several thousand gallons capacity or equal to say four hours demand of the works, are filled with the raw water and a measured amount of water carrying the proper quantities of lime and soda is added with thorough stirring. After the adequate period of reaction and settling has elapsed, the softened water may be decanted off by a floating valve for use. This simple and easily controlled method has nearly all the advantages of exactitude and satisfactory result, but in some cases is slightly costly in labour and insufficient in output. Continuous water softening plants should have very efficient filtration devices, layers of quartz sand, wood-wool, coco matting on frames, etc. In the earlier stages of precipitation the carbonates and hydroxides are in an extremely finely divided or even colloidal state, capable of passing freely any industrial filtering arrangement. After a time there ensues a stage of aggregation and settlement, a process usually under- estimated. It is probably a good principle to mix the fresh raw water and its reagents with the sediment of previous batches, a method which also assists in the removal of suspended oily matters where such are present. Upward filtration is preferable to downward flow. There are no very essential differences between commercial types of lime-soda softening plants, the devices for adding the reagents constituting the main variations in construction. Among such details are :— a. Weirs, whose widths are capable of regulation, automatic or otherwise. Pumps, delivering from reagent tanks. Valves, mechanically controlled. Ball taps. Tumblers or tipplers, i.e., troughs actuated by the filling of the water and consequent over-balancing. f Water wheels carrying dipping buckets, etc. The reagents—lime, soda ash, or caustic soda—are often contained in troughs with a perforated base and having the water delivered at the bottom. It is plain that all these apportioning gears must be reliable and it is an interesting question how far the results of everyday working of softening operations are efficient.

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Page 40

16 SOFTENING TESTS.

In a series of trials conducted some years ago by an insurance organisation, seventeen different commercial plants were tested ; no example of the Permutit system was included. Chemical analyses of the raw and treated waters were made, together with determinations of the temporary and permanent hardness at each stage, and full details of the nature and amount of the reagents employed, costs and mode of working. The results, regarded as a practical industrial operation of great importance, were illuminating. Of the seventeen plants all but two were found to be using insufficient lime. Lime is required for the following functions :—

1. To neutralise the free carbon dioxide. 2. To reduce the bicarbonates by combining with the half- bound carbonic acid. 3. To convert the magnesium salts to hydroxide.

The alkalinity of lime water at ordinary temperatures is about 0.125 per cent. or 87.5 grains per gallon. It would seem that in most cases only the second of the above requirements had been apprehended. Certain plants had _ considerable amounts of steam or condensation water furnished to them, but apparently with little or no advantage, as the softening of water by the aid of heat can only be partial at the best, and is inefficient at moderate temperatures. Some selected cases are appended for illustration :—

SUPPLY. DELIVERY. TEMP. PERM. TOTAL. TEMP. PERM. TOTAL. A. 8.8 5.9 14.6 14.1] 14.1 B. 15.5 25.3 40.9 25.4 2.5 27.9 C. 15.1 33.1 50.3 31.3 3.7 35.0 D. 13.4 0.0 13.4 4.4 0.0 4.4 EK. 13.9 6.5 20.4 — 3.5 4.4 7.9 F. 21.1 55.0 76.1 11.6 28.8 40.5 G. 13.5 Va 20.6 0.9 0.0 0.9

The following notes on these cases will be instructive and useful :— A. Soda-ash only used ; the conversion of the permanent to wholly temporary hardness indicates the necessity of lime treatment. B. Caustic soda employed ; the water requires a combined lime-soda process. C. Soda-ash reagent only, ona pit water. Lime is necessary or alternatively a caustic soda treatment. I D. A well water, with no permanent hardness, given lime only ; the raw water being alkaline, the excess of lime left some temporary hardness.

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K. Lime and soda used, but not in the strictly correct proportions. F. Lime and soda, but both in insufficient quantities. G. Caustic soda only, producing over alkalinity in the finished water. Part of the caustic should be replaced by lime. How far may the above illustrative cases be regarded as representative ? Some of the foregoing types of plants are installed on hundreds of undertakings, and it seems impossible to resist the conclusion that the general working of water softening apparatus is defective and capable of improvement. Mr. David Brownlie has stated that of 250 boiler plants inspected and tested by him, only 43 had water softening apparatus working in conjunction, and of these eighteen only were being operated correctly. The average hardness in nearly four hundred cases was 11 degrees. The modern extension of water-tube boilers and the increase in evaporative duty will intensify these questions of filtration, softening, and expulsion of dissolved gases in industrial waters. It is perhaps inevitable that processes of this kind, involving many variable factors and necessitating some regular control, though often unskilled, should reveal inefficiency, and it is probable that the more automatic character of the Zeolite systems—though these have disadvantages and severe limitations—has led to their extension. Well worked lime-soda systems are capable of reducing the hardness to about 3-4 degrees. It is not beyond the ability of an intelligent engine-tender to take a Clark soap test for total hardness, say, once weekly ; provided the soften- ing plant is correctly started up, such an employee might be taught to check and book the working from time to time. Owners of softening apparatus must not assume that once these are put into operation no further attention need be given. It is plain that wrong working of these devices may not merely prevent the proper benefits being derived, but may actually introduce evils of a special kind. In general it may be said that the softening of even bad waters may be conducted at less cost than the purchase from, say, a public supply.

ZEOLITE SOFTENING.

The zeolithic systems of water softening present some easily seen advantages over the lime-soda methods. The plant is somewhat simpler, complicated apportioning devices being absent ; the softening is usually rather more perfect, even zero hardness being attainable ; there is possibly less skill required in operation. The apparatus is of moderate size, quicker in action, self-adjusting to variations in hardness, and makes no sludge. The method, however, has its defects. It is not suitable for extremely hard waters, which must first have a

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Representing the complex silicate by the contraction ‘‘ Pm,” the chemistry of the zeolithic softening processes may be summarised as below :—

1. Sodium Zeolite + Calcium Bicarbonate = Calcium Zeolite + Sodium Carbonate. Na,Pm + CaH, = CaPm + 2NaHCO,; and similarly for magnesium carbonate. 2. Sodium Zeolite + Calcium Sulphate = Calcium Permutit + Sodium Sulphate. Na,Pm + CaSO, = CaPm + Na,SO,.

Magnesium Chloride would yield Sodium Chloride by replacement. Thus the salts passed forward will be mainly carbonate, sulphate, and chloride of sodium, and it is certain that in some cases corrosion troubles have resulted therefrom ; season cracking or embrittling may follow. The zeolite process requires cleaner waters than can be dealt with by the older method, some supplies demanding a prior filtration for suspended matter. The bed of permutit mineral is an expensive investment, and must not be ruined by improper usage. There is no influence on dissolved carbonic acid gas in this method and the soluble sodium salts produced, though less objectionable than the lime and magnesia eliminated, are injurious in boiler feedwaters. The sodium bicarbonate equivalent to the original temporary hardness is a corrosive agent in boilers. The lime-soda process tends to fix oily contaminations, a most dangerous impurity in boiler waters ; the permutit method has no effect here. Iron salts, an un- desirable impurity to steam raisers, bleachers, and scourers alike, are well removed by the lime-soda principle. A recently introduced material of the zeolithic type is ** Doucil,’’ which is described as a double silicate of sodium and aluminium containing roughly 20-22% of alumina; it is claimed that the substance is not an artificial zeolite, but a “synthetic alumina silicate’? made by applying modern knowledge of the chemistry of colloids to the production of a base exchanging material in the form of a perfectly homo- geneous jelly. This is afterwards converted to a granular mass of very high porosity. The latter property renders the material useful as a vapour absorbent as well as a water softener. It is said that 1 cwt. of Doucil will reduce to zero hardness 2000 gallons of water of 10 parts per 100,000 (i.e., 12.5 degrees), between its regenerations ; each such regeneration requires 8-9 lbs. of common salt per cwt. Doucil. More recent methods of preparing base exchanging compounds than by methods involving fusion are illustrated by the following abstract of a patent specification :— Solution of alkali silicate of not more than 40°Tw. is

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mixed with a solution of borax (not more than 20°Tw.), or acidic salts of alkalies other than sodium aluminate; after the mixture has set the resulting gel is dried and washed.

The rather exceptional cases of waters containing sodium carbonate or bicarbonate in solution are characterised by their alkalinity and usually low hardness; they may be corrected satisfactorily by additions of lime or calcium chloride. Acid waters of peaty origin do not require treatment for hardness, their corrosive properties are best checked by small additions (about 1-2 grains per gallon) of silicate of soda. Caustic soda treatment of hard water is necessarily more expensive than the ordinary combination of slaked lime and soda ash, but is useful in difficult cases of permanent hardness or much free carbonic acid. Waste caustic from mercerising works is some- times available for this purpose. Caustic soda alone will effect a satisfactory softening of raw water having temporary and permanent hardness in approximately equal amounts. The practical cloth scourer will recognise the hardness of the water supply by the refusal of his soap emulsions to rise into free lathers, by the sudden “ cracking ”’ of the frothy emulsions on admitting the washing off waters, and by the extra, even excessive quantities of alkali needed to produce lathering. The scouring liquors preserve the characteristic splashing and rattle of a watery medium rather than the dull muffled murmur of a genuine emulsion ; it is sometimes possible, even when one’s back is turned to the machine, to detect what is happening in this way. The scour liquors are milky rather than soapy. In extreme cases the boardwork and rollers of the plant become coated with a sticky greyish layer which simple analysis shows to be a basis of lime and magnesia soaps with greasy flock, a contamination often removable only by actually scraping the surfaces. Piece goods scoured under these conditions show uneven or cloudy places or patches of differing depth of tint in dyed goods. They lack brightness and frequently smell, especially after warehousing ; the handle, to an expert percher, is also defective. In an indigo vat, for example, pieces con- taining lime and magnesia soaps exhibit bright and glistening patches easily seen as the cloth runs below the surface of the liquor, and often a scum collects, which again proves to be primarily the insoluble mineral soap basis referred to above. If the fabrics are scoured in an ordinary dolly, the contamina- tions tend to run warp-ways as patchy streaks, owing to the drawing out action of the rope of cloth as it runs through the machine, but map-like areas of irregular outline also occur. In severe cases there is no alternative but treatment of the goods by a bath of slightly warmed dilute hydrochloric acid in a jigger, followed by very thorough washing and rescouring with proper water.

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The scour should be a double operation :—1l. Alkali only at the outset. 2. Alkali and soap jointly, followed by efficient washing down by soft water.

It is interesting to observe the special effect of certain geological formations on the water supplies originating in their areas from the special strata. Thus the Millstone Grit series which forms the high level areas of the West Riding of York- shire on one side and the East Lancashire district on the other, furnishes water supplies to the woollen and worsted industries of the one and the cotton manufactures of the other, of a highly characteristic type. The following is the analytical average of seven West Riding supplies, all of moorland origin :—

TYPICAL WEST RIDING WATER.

Calcium Sulphate 2.75 Calcium Carbonate 0.75 Magnesium Carbonate 0.75 Magnesium Chloride 0.90 Sodium Chloride 1.33 Magnesium Sulphate 0.66

Grains per gallon 7.14

with traces of silica, iron, and alumina. It may be that some part of the mineral bases, lime or magnesia, exists in these waters as salts or organic acids derived from the decomposition of the cellulose of the peat tissues ; such acids, of somewhat obscure composition, are described as humic acids. There is some ground for concluding that the production of Formic acid in these waters is a stage in the breaking down of the vegetable fibre. The waters of this peaty type are often slightly yellow or brownish. They take up some oxygen from a solution of _ permanganate of potash and are slightly corrosive on lead or , iron pipes. The total hardness is approximately 3-5 degrees, the per- manent exceeding the temporary (34-24). There is little dissolved carbon dioxide, and there is a little acidity, due to the peat acids. Many factories lying high up on the Pennine watershed enjoy abundant supplies of water of this type, requiring no treatment other than sedimentation or filtration against suspended matter or flood-borne detritus. In the rivers or canals at lower levels, the dissolved and suspended contaminations rapidly increase ; the hardness rises to 9-10, or more, and the suspended filth from sewage or industrial effluents takes on the character of actual mud, etc. The lower levels of these districts lying on the Coal Measures of the Carboniferous System supply wells and boreholes of greatly varying nature; waters of 10, 12, 18, etc. degrees of hardness

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are common, the permanent exceeding the temporary, some- times in a curiously constant ratio. Similar conditions to these are present in the Lowland Woollen district of Scotland. The West of England and the Midland Hosiery area are afflicted with an extremely variable series of waters, many of high degrees of hardness and very commonly necessitating chemical treatment.

FILTRATION. It is extremely desirable to filter textile waters ; all turbidity or suspended matter is dirt from the textile point of view. The kind of matter carried in this way varies with the source. Rain

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water, if collected from roofs, carries atmospheric dust and soot, the dust being in the neighbourhood of smoky towns mainly flue ashes in an extremely fine state of subdivision ; such ash may by partial solution harden the rain in a surprising manner. Spring waters may carry humus and fine silt ; moor- land waters, particularly, have much flocculent peaty matter in suspension. River waters are especially turbid, with mud of a complex kind, even fine flocks of the textile fibres and sediments from dye-vats and all the impurities of sewage ;

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quite commonly they are oily also. Canal water in manue facturing districts is a little less turbid, but may be equally hard and generally objectionable. Filters are of various types, and act on as diverse principles. Coarse flock and fibrous matter is removable by screens, preferably of a rotating type, and fitted with cleaning brushes or other devices. Chemical filtration by the use of precipitants, e.g., Aluminium Sulphate, Alumino-Ferric compounds, etc., is practised on the large scale for continuous operation. The filtration for public potable supplies is usually of the sand-bed kind, and it is quite possible to instal sand filters near the scouring plant, and thus ensure a clear supply for washing off. Such a filter, capable of construction in two-inch plank by an ordinary millwright is figured on this page. The water supply from a one-inch tap falls into chamber A ; the filter chamber proper has a perforated board as its base, and is graded with sandstone, quartz, crushed flints, etc., in three sizes :—one inch, half-inch, and grit. The overflow leads to storage tanks capable of holding 3000 gallons or more. A simple device of this kind installed near the scouring plant, so as to avoid long pipe-runs, will ensure the stoppage of all suspended matter, and supply three or four machines in continuous operation. It should be emptied and washed down by reverse flow frequently—weekly if the supply is much polluted—and the filter bed renewed, say, every twelve months ; the top layer of finest material may be scraped over more often. It is remarkable what an amount of fine peaty silt and flocculent material this filter will stop, even from a public supply. It is quite common to find this peaty sediment mistaken for iron corrosion. Iron rust is a variable mixture of ferrous and ferric oxides with water of hydration approximating to the composition :—80-—90 oxides of iron, 20-10 per cent. water. The subject of filtration is becoming so important in textile practice that it is desirable to expand the introductory matter given above. The scouring departments are primarily con- cerned with the supply of soft and clear—often speckless— water; and the effluents produced in the scouring operations may require coagulation and precipitation with a subsequent filtering process prior to their final discharge. In this latter case, rough beds of boiler ashes are usually employed for the watery portion of the acidified seak liquor and layers of sawdust for the grease residues. For the purification of water supplies many materials are used, e.g., clean sand, crushed quartz, gas-house or furnace coke, charcoal, shavings of wood-wool, textile fabrics such as canvas or coco matting, artificial masses containing magnetic oxide of iron, sponges, etc. Filters of this class depend for their efficiency, apart from simple straining action, on the formation of a peculiar jelly-like mass of a low

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type of plant life within the pores of the medium. This phenomenon, well known in the large sand beds of the filters of public supplies, is necessary to their efficient operation, and after renewals two to three days are allowed for its development. The removal of foreign matter in the raw water by this agency is exceedingly thorough, extending even to the bacterial content ; when over-developed, the gelatinous film must be cleared away, or fresh filtering medium substituted. I In the modern Rapid Mechanical and Pressure Filters, an artificial film of similar type is produced by first rendering the raw water slightly alkaline, if necessary, and then adding a suitable proportion of an aluminium compound as coagulant and precipitant, e.g., aluminium sulphate or alumino-ferric. Such plant is made to filter at greater rates than the older methods, but large initial expense is incurred and it is quite easy to pass fine precipitates of the coagulant into the supply, if the plant is excessively or negligently worked. Matter of this kind is of course as dangerous in textile work as any mineral soaps due to abnormally hard waters. It should not be forgotten that ‘“ plant ’—water softeners, filters, and the like—requires regular and efficient attention just as the ordinary -running machinery of the works.

STORAGE OF WATER.

The storage of water, raw, filtered, or treated, requires some notice. As a rule, the water of a textile works is taken from a dam, pond, or reservoir fed from a stream, the volume of storage being less the greater the constancy of flow from the source. It is plainly better to accumulate under these more or less stagnant conditions as little as necessary, for special troubles due to sedimentation, growths, etc., may develop. The ordinary mill dam, particularly on the lower reaches of a stream, is often a deplorable spectacle of filthy residues of mud, sewage, and general refuse with discoloured oily water, sometimes soapy, carrying surface scum, the common sink of pollution and decay. Originally many of these were planned as reservoirs for water power and are of the roughest construction, often mere local depressions in the earth ; in course of years dense masses of sludge are formed therein, and a condition ensues somewhat resembling the treatment tanks of a sewage works. The writer has, in consulting work, seen instances in which a proving rod could be easily thrust by hand ten feet down into such a deposit ; in which also small shells, worms, young fish and even frogs were passed into the works supply. Vegetable contamination—surface scum of algal type, loosened masses of pond weed, or decayed leaves, etc.—is so common as to be almost normal. Pollution of this type may be very trouble- some; it can be so pronounced that washed-off pieces after

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scouring show slight discolouration—greenish yellow due to the plant chlorophyll—from the water. Storage dams for crude water should be provided with some straining device at the exit to remove all solid impurities; a perforated casing of brickwork or planking built round the outfall pipe, and filled with coke, gravel, etc., is useful. Wood-wool is effective and can be easily forked out when choking occurs, but any arrange- ment will require regular attention. Abnormal vegetable growth in dams may be checked by chemical poisoning ; the popular provision of a couple of swans for this purpose is a poetical sentiment. Taking advantage of a week’s stoppage at a holiday season, the pond is treated with chlorine by placing a tray or bag of bleaching powder at the infall, or by towing a porous sack through the water; the after addition of some common vitriol is useful. This is allowed to act on the vegetable growths for a day or two, or longer if convenient, and it may be desirable to lower the volume of water to secure a vigorous action. The dam may then be run off and cleaned of deposits as perfectly as the circumstances will allow. Crude Sulphate of Copper is an effective poison for vegetable growths in these cases. Dams subject to this trouble will need repetition of the treatment at proper intervals. There is in the industry an all-round neglect of the matters of the present section. In a case of peculiar fabric stains developed at the scouring end of a first-class worsted manu- factory, the writer ascertained that a filter and cistern, built on a roof about 40 feet above ground level and originally supplied with a medium of sand, gravel and charcoal, had not been cleaned or renewed for over twenty years. It is a not uncommon belief in the finishing and dyeing trades that troubles are unusually prevalent in the autumn season, when water supplies are more than ordinarily polluted by deficient rainfall, extra plant growth, and various kinds of decaying vegetable matters. Cases of choking of mains would be less frequent if care were taken to strain out suspended solids at the intake. It is a frequent delusion that the deposits of choked water mains are the rusty products of the corrosion of the pipes. In the mains supplying the moorland waters of the West Riding there is a large amount of peaty sediment of a finely divided or even colloidal character. The storage of a filtered or softened water need not in most works be on so extensive scale. Cemented tanks, or reinforced concrete, are useful for large demands ; slight hardening of the water takes place in these when newly erected. In other instances, wooden cisterns holding up to 5000 gallons each are suitable. Such tanks are made of many varieties of timber and are preferable for textile uses to the iron tanks often employed. Circular vats are cheaper than the square or

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rectangular forms, as timber of smaller sections is available for their construction. All woods consist fundamentally of ligno-cellulose with certain proportions of gummy or resinous substances and in special cases some tannins and colouring matter. For tank or vat making, the ideal timber will not convey any colour, taste, or smell to the liquid stored, nor change in any way its chemical nature. It should further

Fie. 5a.—FLOCK CATCHER.

Fig. 55—ROTARY PUMP. LOoNGWoopD ENGINEERING Co., LtTp. HUDDERSFIELD.

suffer little or no attack of its own substance. These difficult criteria are not fully met in practice, but the ordinary textile conditions of pure water or dilute solutions are fairly fulfilled. As a rule, dilute acids at the ordinary temperatures affect woody tissue but slightly, but alkalies almost invariably extract colouring matter, gum and resin, and the tannins ;

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their effect is much enhanced at higher temperatures, the absorptive capacities of different woods vary very greatly, and the degree of swelling is also irregular. Certain woods, e.g., redwood, become brittle in special solutions such as weak sulphuric and hydrochloric acids. Cypress is a highly resistant timber, and pine is generally applicable ; pitch pine is excellent for cold water tanks. Oak has good mechanical and damp- resisting qualities, but is troublesome in persistent colour bleeding, particularly in soapy or alkaline media. Im fact, caustic or warm alkaline liquors are unsuited to storage in wooden vessels. Fir is more proof against sulphuric acid than any other timber. All woods due to absorption expand in cold water or water solutions, a fact which renders possible their tightness even when containing many tons of liquid.

RECOVERY OF POLLUTED WATERS.

The general increase of modern industry and extensions of particular works have led to more than ordinary demands upon local sources of water supply, and hence the problem of recovering water from various works operations for re-use has arisen. The principal available sources of used water are :—

1. Condensations from steam engines or heating systems, drainages from steam mains, etc. 2. Effluents of varying quality from scouring, bleaching, dyeing or finishing operations.

The waters of the first class are liable to be contaminated by oil and pipe corrosion. In the second class it is advisable to take the purer portions only for recovery, i.e., the wash-off waters from the later stages of piece scouring operations. The methods of purification are based on the principles elaborated in the preceding pages. Some screening or sedimentation or

filtration will be needed, but usually no actual softening; a

precipitation by chemical means such as alumino-ferric may be required, and subsequent decantation or filtration. The final product can be almost free from colour and suspended matter, but some alkalinity remains due to soda ash, which is in most cases unobjectionable. .The recovered water should be sufficiently free from organic matter as to be non-putrescible. Such waters are quite suitable for many textile operations such as the first or second bowls of wool washing.

BOILER FEEDS.

The wet processes of cloth finishing are dependent upon the steam supply in a measure second only to the provision of good and abundant textile water, and serious troubles may directly originate at the boiler house. Hard water causes scaling in

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the boilers and economisers ; corrosion of the plates and fittings, overheating and distortion of the flues, tubes, or the boiler shell, and priming or foaming may all occur with faulty boiler feed water. The scale forming constituents are mainly the hardness salts of the water, viz., sulphate and carbonate of lime, carbonate of magnesia, with any silica and oxides of iron and aluminium present ; easily decomposed bodies like magnesium chloride may contribute the basic portion to the scale, yielding hydroxide. The soluble salts, e.g., sulphates of soda and magnesia, chlorides of calcium and sodium, carbonate of soda, etc., have no scale forming tendency, but in excess tend to cause foaming. It is recommended to keep the specific gravity of the boiler water at not more than 1.04 or less in high pressure installations, making frequent tests by the hydrometer. These soluble saline constitutents of the water may contribute to the

Fie. 6.—EFFECT OF SCALE.

internal corrosion of the boiler, and a very slight coating of scale is undoubtedly protective in this respect. The whole subject of corrosion and scaling in boilers has been the occasion of many fallacies. It is still common to encounter elaborate calculations based upon the inferior heat conductivity of boiler scale as compared with metal and facile conclusions of excessive coal consumptions deduced therefrom. It should be clearly understood that scale is to be prevented, not merely on grounds of loss of efficiency, but mainly because of serious or even dangerous overheating of the surfaces of the boiler. It is not in the first place a question of waste of fuel, but of wear and tear, reduction of the life of the plant, and of safety in working. In a clean boiler the temperature of the furnace plates is not far from that of the water; quite thin coatings of scale may create temperature differences amounting to hundreds of degrees. Some experiments by Prof. Schmidt, of the Univ.

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of Illinois, give the following results of heat losses due to scale :—

THICKNESS OF LOSS OF COAL WASTE HARD SCALE. EFFICIENCY. PER TON. 1/50 inch 5.4% 100 Ibs. AIDES 55 8.5% 140 __,, 9.3% ime. 3, RIN C5) LLL Pa © ;, 12.6% pa EAS 5s 15.9% cht ae

Another dangerous impurity in boiler feeds is grease or oil, a contamination unfortunately quite common in textile districts, where the streams furnish large quantities of condensing water and where also much effluent from plants treating seak liquors is discharged. Such greasy matter may be present, not merely as visible floating films, but more insidiously in a state of emulsification. In a boiler it adheres to the heating surfaces and causes local overheating of a severe kind; even in the thinnest films, almost mere traces, it is injurious. Both mineral oils and the animal or vegetable oils are prejudicial, the latter being corrosive as well as the cause of overheating. It has already been pointed out that a lime-soda softener is an effective grease remover ; additions of alumino-ferric to the soda are helpful. It should further be noted that soapy waters are, from the point of view of boiler feed, to be classed as greasy. When boilers are opened out for cleaning, etc., it is important to examine carefully the plates at the water level ; oily impurities usually produce a line of corrosion in this region. The main cause of internal corrosion in boilers, especially those of the high pressure class, is the presence of dissolved gases—oxygen and carbonic acid—in the feed waters. Water dissolves at ordinary temperature and pressure about one part in a hundred thousand by weight of oxygen. If the supply undergoes a softening process, the carbon dioxide is mostly eliminated. Oxygen may be removed by passing the water through masses of iron turnings, or more usually by adding such compounds as tannin extracts. A really bad feed water should be corrected in an external plant, though boiler supplies of a fairly soft and unpolluted kind may have small additions made to the feed. Slight amounts of soda ash or caustic soda are commonly employed and the experience of many thousands of cases has revealed no ill effects of a corrosive nature, but undoubted benefits in respect of scaling, etc. It has been stated that the average hardness of boiler feeds in this country is about 11 degrees; of this figure the proportion of the permanent hardness is important in this connection. A rough rule for boilers near to this figure would be to add from one to two pounds of soda ash for a Lancashire boiler per day, or

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a rather less amount of caustic soda ; this only in the absence of exact chemical supervision or advice. In a case investigated by the author, the boiler staff, though provided with a small tank and pump for this purpose, had followed the practice of putting in about 56 lbs. of soda ash all at once on refilling the boiler after the periodical runs of six weeks. It is hardly necessary to say that serious priming had occurred. In another case, the engine-tender admitted the daily addition of a bucket of soda ash, say 20 lbs., to the hot well, and again the result was immediate and vigorous priming extending along the steam mains to the dyehouse and the scouring shed. Priming, or foaming, is the excessive or violent ebullition of the contents of the boiler, usually resulting in carrying along the steam mains a dirty froth of the impurities of the feed and the corrosion, with disastrous effects to the dyeing and finishing operations. It is far commoner in textile works than the boiler staff is ordinarily prepared to admit. It may be caused by dirty feed water, especially with greasy or soapy admixture ; too high a water level in the boilers, i.e., too little steam space; forcing the boilers ; presence of suspended stuff of a colloidal nature, e.g., scum, muddy or peaty matter ; excess of saline constituents, etc. Fluctuations of steam demand cause foaming when very severe. The sudden lower- ing of pressure in the steam space produces violent ebullition, because the water is at a higher temperature than the steam at the reduced pressure ; the surface layers of the water are lifted bodily in the form of a froth. Such foaming is more persistent the greater the contamination of the boiler water. Many cases of leaky valves, escaping joints, acute steam hammer in the mains, etc., are due to priming in the boilers. Lesser degrees of foaming occur often without becoming evident to the dyeing or finishing staff, except by defects in the goods ; these are revealed as irregular map-like areas of different shade to the general level of the fabric, where the deposition and local absorption of the filth transported in the frothing of the steam has taken place. <A serious example of this kind occurring in a large woollen mill was traced to the priming of the boilers ; this was due to the addition of a large quantity of soda ash on filling the boiler after cleaning, together with one or two buckets of fuller’s earth. After a certain period of running—the boiler pressure was 160 lbs.— a copious formation of colloidal alumina compounds took place with consequent foaming, and further damages to the materials in work. The fuller’s earth was added by the attendants under the impression that it prevented or loosened the scale. It is interesting to observe—as an illustration of the caution required in these affairs—that the presence of excessive amounts

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of aluminium hydroxide in the boiler water was at first ascribed to the discharge higher up the stream of the washings from mechanical filters using alumino-ferric precipitation ; the boiler staff in the first instance, concealing the fact of their addition of fuller’s earth. Another method of controlling the boiler water is based upon an electric method of determining the conductivity, which is roughly proportional to the concentration of dissolved salts ; at a given ratio the boiler is blown off.

Steam. As a useful preliminary to any discussion of steam generation and utilisation in textile works, it is desirable to append some account of the properties of steam in the scientific aspect. It is familiar knowledge that the conversion of a liquid into its vapour requires heat of transformation or Latent Heat, the change taking place at a constant temperature until completed. Further, that this temperature or “‘ Steaming varies greatly with the pressure. Taking the ordinary atmospheric pressure of 14.7—approximately 15 lbs.—per square inch, or one atmosphere by gauge, the corresponding boiling point is 212 Fahrenheit, or 100 degrees Centigrade. The principal properties connected with this temperature and pressure are as follows :— Pressure :—14.7 lbs. per square inch, or one atmosphere above vacuum. Temperature :—212°Fah. or 100°Cent. Total Heat from Water at 32°F. :—1146.6 B.T.U. Heat in Liquid from 32°F. :—180.9 B.T.U. Heat of Vaporisation or Latent Heat of Steam:—965.7 B.T.U, Density of Steam :—0.0376 Ibs./cu. ft. Volume of 1 lb. of Steam :—26.64 cu. ft. An abbreviated table of the properties of saturated steam within finishing works practice is attached :—

PRESSURE. TEMPERA- TOTAL HEAT ABSOLUTE. GAUGE. TURE. FROM 32°F. I 14.7 1 212 1146.6 20 5 228 41515 30 15 250 1158.3 40 25 267 1163.4 50 35 : 281 1167.6 60 45 293 1471:.2 80 65 312 417750 100 85 328 1181.9 120 105 341 1186.0 160 145 363 1192.8 180 165 373 1195.7 200 185 382 1198.4

Ibs./sq. in. Fah. Brit. Therm. Units.

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The specific heat of water is the amount of heat required to raise unit weight through unit temperature, i.e., 1 lb. through 1°Fah., and is taken as the standard or engineer’s unit of heat, viz., the British Thermal Unit. The specific heat of ice is 0.504 and of steam 0.48, being thus practically one-half that of water as liquid. Considering the fundamental part played by steam, both directly applied to fabrics in the various finishing processes and indirectly for power and heating, it is remarkable how little - exact knowledge of its properties prevails in the dyeing and finishing industry. In addition to this, the serious increase in fuel prices makes it essential that the boiler house should have intelligent study and supervision ; an intelligence which should extend to the steam users in the sheds. The case for the heating of boiler feed waters is apparent from a simple illustration. Taking a boiler working at 75 lbs. gauge pressure and a corresponding steaming point of 320°F., about 260 heat units must be added per pound of water evaporated to raise it to the steam temperature, assuming an average feed at 60°F. Now as it takes 1151 heat units to evaporate water at 60°F. to steam at 320°F., the initial stage represents 260/1151 or about 22.5% of the heat of the fuel; the other 891 units represent the latent heat of change of state. It is patent that it is an economical procedure to secure the 22.5% heating of the feed water outside the boiler, thus increasing the capacity of the boiler for its proper function, that of steam raising. Hence the utility of the economisers working from the other- -wise wasted heat of the flue gases ; savings of 15% of the fuel -are quite possible; but the actual results in practice are round about 12%. The question of superheating steam is primarily a matter of increased efficiency of the power plant and only secondarily useful as a means of preventing heavy condensations in long pipe runs to dyeing and finishing plant. Superheating causes steam to have a higher temperature at a given boiler pressure than the water from which it was evaporated; plainly it secures dryness in the steam, the moisture being itself evaporated. In Brownlie’s tests, referred to later, the average superheat on twelve of the sixty-five plants fitted with such apparatus, was only 38.5°F.; a figure of at least 100°F. is desirable from the standpoint of reducing pipe losses alone. If there are engines in the dyehouse or finishing shed of the single-cylinder non-condensing type—and these are not un- common as drives for tenters, winches, jiggers, etc.—the waste of steam may exceed one-third of the total used, by cylinder condensation alone. Some interesting results of an extended series of tests of boiler plants have been given by Mr. David Brownlie (Jour.

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Fic. 7.—BOILER LOSSES AND WASTAGES.

Wastage due to unconsumed fuel in ashes. 7. Heat waste by internal scaling. Loss by emission of black smoke. 8. Excessive draught and forcing. Bad regulation of damper; excess of cold air. 9. Loss of heat in by-passing. (Best proportion of carbonic acid gas:—12%.) 10. Radiation losses where lagging is absent or Grate losses, owing to uneven or over thick imperfect. fuel bed; or bare places. 11. Heat waste in blowing off. Leakages in brickwork and settings; and at 12. Maintenance of proper working level of furnace doors. water. Losses arising from sooty surfaces ;—Boiler 13. Waste by leaky steam fittings. shell or tubes, and economiser.

tf ©

33

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Soc. Dyers & Col., April, 1923). The Lancashire boiler is the favourite steam generator in the dyeing and finishing industry. The grate area is about 40 square feet per boiler burning some 21 Ibs. of coal per hour per square foot ; the coal has a calorific value of nearly 12,000 British Thermal Units, and roughly 10% ash content. On the sixty-five plants examined, the evaporation was equal to approximately 760 gallons per hour for the standard 30 feet by 8 feet Lancashire boiler. Economiser savings varied greatly, the mean being 11%. “The true net working efficiency of the whole of the 65 plants was approximately 61.41%; that is to say, for every 100 lbs. of coal put into the fire, 38.6 lbs. were wasted,...... the figure that can be . obtained using modern methods is 75%. It can be safely said that 20% of the coal bill in the dyeing and allied industries is waiting to

be saved by the adoption of almost elementary methods of equipment and control of steam boiler

STEAM MAINS.

Very severe losses may occur in the steam pipes supplying dyehouses and scouring sheds. Very nearly, a square foot of bare steam pipe may lose under average conditions one pound of steam at 100 lb. pressure per hour; a wastage reduced to one-tenth by suitable covering. Viewed from another aspect, this would amount to a coal wastage of 400 lbs. of coal per annum for each square foot of unprotected pipe. Good compositions for heat insulation of steam mains are based on mixtures of magnesia and asbestos, about 6 to 1, and a final cover of canvas coated with bitumen paint. For all reasons, steam pipes should be kept to the minimum diameter consistent with proper flow. If the fuel costs of the works are to be reduced to a minimum, the heat requirements of the factory as a whole must be taken into account, as well as the power generation. As a rule, cloth finishing works need for their operations and for warming of rooms more heat than for the mechanical driving of the plant, i.e., the power demand is usually less, often very much less, than the steam demand per se. It will be necessary in the future to employ steam meters in these directions more frequently and to find, for example, the approximate require- ments in steam, power, and other primary essentials per piece of fabric finished. At present there is a total lack of such published data in the technical literature...The conversion costs taken in the late War are a step in this direction. Some few years ago, an enquiry embracing about 20 cases, mostly spinning mills, showed an average fuel consumption on com- pound engines of nearly 2.7 lbs. of coal per indicated horse power. At high pressures and with superheating, this figure was reduced to 1.45 lbs. and steam for other purposes added 0.6 lbs. per i.h.p. per hour to this, making a total of say 3.3 lbs.

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or 2.05 lbs. in the latter case. In adyeworks the steam demand for heating and boiling would be considerably increased, and the problem is solved sometimes by the provision of in- dependent boilers; the higher pressure for the power plant, the lower supplying heating steam only. Under certain circumstances, the required heat may be obtained from the exhaust of the driving engines, when worked non-condensing. On other occasions steam may be abstracted at some convenient intermediate pressure. It is apparent that the calls for power and for heating may not be correlated either for quantity or time, and the heating demands may be so divergent as :— warming up air for tentering, water for scouring, boiling for dyeing, etc. Plainly, therefore, the utilisation of the latent heat of a steam power plant for the general purposes of, say, a dyeing and finishing works, is a problem only to be solved by inquiry on the spot. Steam is employed in the scouring and milling departments principally for the heating of soap and alkali solutions, and for the supply of warm washing-off water. In the later stages of finishing it has also special functions as in blowing or decatising, etc. The generation of steam, as regards the running and maintenance of a boiler, are matters outside the immediate subject of this book. The question of the best boiler pressure for finishing purposes is, however, both relevant and instructive. One British Thermal Unit of Heat is the amount of heat required to raise the temperature of 1 lb. of water 1° Fahrenheit. When therefore 1 lb. of water is raised from freezing-point to boiling, it absorbs 212-32 = 180 B.T.H. of heat. To convert this amount of water into steam still at 212°F. will now require another 966 B.T. units of heat. After this, further gains of temperature are obtained for a heat supply of rather less than half a B.T. unit per degree F. Thus 1 lb. of steam at the atmospheric pressure would liberate 966+ 152 = 1118 units of heat to water at the ordinary temperature of 60°F. If the boiler pressure is 50 lbs. gauge or 65 lbs. ahsolute, the total heat from 32°F. being now 1173, as against 1147 at the ordinary boiling-point :—212°F.; then, obviously, only another (1173- 1147) or 26 units more of heat are obtained from such 50 lbs. steam, say, for the purpose of heating water, at 60°F., or other temperature. And again, if the boiler pressure is 160 lbs. or 175 lbs. absolute, the total heat of the steam now being 1195, then (1195-1147) or 48 more units of heat are obtained for the purpose of warming the water supposed at 60°F ., as before. Plainly, when steam is required merely for water heating, the proper course is to make relatively great use of the large latent heat ; high pressures are not required or economical ; any excess pressure only serves the function of overcoming pipe friction in a slight degree and diminishing condensation, quite

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ah a, PRESSURE

FOR, rms SURE 7. a ow PrEssurE Pire L OUTLET BRANCH (av pack) - = >» oe WITH PASSAGE GUTLET

tee PRESSURE a8)

I VALVE SPINDLE

Fig. 8.—REDUCING VALVE.

(Hopxinsons LimiItED, HUDDERSFIELD.)

ACTION OF VALVE.—The low pressure is maintained on the underside of the diaphragm “D ’’ by means of the low pressure balance pipe “ L.’’ Any drop in pressure allows the main spring “$*’ to open the pilot valve “ PV’’ and the high pressure steam passes along the external pipe “ H’’ to underside of actuating piston “ P,’’ thus lifting the main valve “V ”’ which maintains the desired reduced pressure. Where the demand for low pressure steam is intermittent, the partial closing of regulating valve * RV ’”’ prevents any sudden flow of steam to underside of piston “ P.’’

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a minor factor. On the other hand, economical power depends on the use of high pressures. It is an interesting experiment to put a thermometer in the folds of the wrapper on a blowing machine; it will be found that, whether the machine is fed from a boiler at 50 lbs. or 160 lbs., the temperature at the wrapper is practically 212°F., i.e., the ordinary boiling-point ; the steam in both cases expanding down to atmospheric pressure cools to the corresponding temperature, viz., normal boiling-point.

oni 23 7 15 AY Ay <<. 37 35 a 20 19 1 33 4 = ae 24 Ar 7 ‘ i 9 ai y I WANE 16 \ ie 34 y RS Z, 13 17 25 Es 12 ) i =e 7 y I 26 36 SONNY 6 } 28 <7 V S YY LY I I ce 4 GJ I 13 7 mS , 1 I i| LI 31 29 8

Fig. “R’’ REDUCING VALVE. (Horxinsons LimiTED, HUDDERSFIELD.)

If a boiler has to provide both power for driving machinery, steam for heating air for tenters, for blowing machines and press ovens, for heating scouring-water and for dye-vats, and for factory heating, etc., a compromise must be adopted ; this is variously done at from 50-100 Ibs. gauge pressure. But high pressures in finishing and dye-works cause trouble by priming in the boilers, and carrying dirty corrosion, etc.,

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through the pipe system into the vats and plant. A modern method of meeting this situation is to use a power generator of high pressure type, exhausting, not to a vacuum, but to, say, 50-60 Ibs. only ; this is then supplied to the dyeing and finishing departments for general heating requirements, where the enormous latent heat of the steam is most efficiently employed. In these days of dear fuel, this system, in one or other of its forms. is well worth the attention of owners of works. A frequent source of trouble in all forms of plant using steam for heating purposes is the condensation in the pipe-runs. It is a common practice, for example, to run a steam main above a bench of scouring machines, and drop an inch branch-pipe down to the water supply of each machine, fitting with valves. In washing-off a set of pieces, the scourer adjusts the steam and water taps until the temperature is considered suitable. It will invariably be found that the 6, 8, or 10 feet length of vertical steam pipe is carrying condensed water with rust, dirt, boiler softener, etc., accumulated during the period of resting ; the final effect is to blow this matter on to the pieces under- going scouring, with the usual result of mysterious stains, often in this case confined to the pieces nearest the end of the machine. Steam connections of this kind should always be continued below the junction with the water supply, and a second blow-off cock fitted there. Before turning on for washing purposes, the pipe should be cleared of condensation at this lower cock for a few seconds. There are many different arrangements for hot-water supply in textile operations, and in most cases great waste of heat is incurred :— 1. The system of open tanks with a jet of live steam delivered near the bottom, often from a perforated pipe. In this case there are severe losses from the surface of hot water by evaporation and by radiation, followed also by the evils of condensation on to neighbouring surfaces. Moreover, there is possible contamination from the steam supply referred to above. It necessarily also means storage more than corresponding to the average demand for heat, and is further wasteful on this account. 2. An open tank heated by a closed steam coil in the bottom. This prevents steam contamination, but is otherwise practically as wasteful as (1). 3. A closed heater—of a plate or tubular type—of a size proportioned to a little more than average demand, with a small storage fora peak load. This plan is much more economical; exhaust steam may be used, as pressure is not required in accordance with the general principles laid down at the beginning of this section.

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Mere gravity circulation by the difference of density of hot and cold water may not be rapid enough for a heavy demand on the storage. The special circumstances of a particular plant should be considered in this respect ; it is possible that a system using exhaust steam and closed storage tanks with pumping circulation of the heated water may prove the most efficient in practice. The cheap fuel of the pre-war period was responsible for a good deal of neglect of heat economies in textile works. In the storage of hot water it is essential to insulate the tanks against heat losses by radiation, etc. A non-conducting covering of from 6—9 inches will reduce such losses to not more than one-twentieth pound of steam condensed per square foot. In other words, a large tank might suffer a fall in temperature per hour of not more than 5°F. When water is heated by direct steam, as is common in dyeworks, the volume is much augmented by condensation. A simple calculation shows that 100 gallons raised from freezing- point to boiling-point by this means adds nearly 19 gallons to the bath. The process is also very noisy, but this can be diminished by leading the steam pipe into a perforated box containing pebbles, etc. As compared with indirect means of heating, it is of course an economical method. The Fuel Economy Committee of the F.B.I. give the follow- ing table of certain heat losses in boilers using an ordinary bituminous coal, the wastages being expressed as percentages of the total calorific power of the coal, which might be assumed as about 11,000—-12,000 B.T.U. :—

GOOD BAD

PRACTICE. La PRACTICE. 1, Heat in blow-down water... ‘4 2% Carbonaceous matterin ash and clinke 6% i, Smoke and incompletely burnt gases 4% a Heat dissipated by radiation, etc., from boiler setting Se a 6%, 0.5% I Moisture in steam me a 2%, 4.5% I Latent Heat in water vapour from coal 4.5% is’, Sensible Heat in chimney gases ne 36% COMPOSITION OF SEA WATER. Sodium Chloride 2.700 Magnesium Chloride 0.360 Magnesium Sulphate 0.230 Calcium Sulphate 0.140 Potassium Chloride 0.080 Calcium Carbonate 0.003 Magnesium Bromide 0.002

Total © 3.515 Water 96.485

Page 64

Fic. 10.—THERMOSTATIC CONTROL. (Messrs. Hopxinsons Liutrep, HUDDERSFIELD.)

4

Page 65

4] CONTROL OF TEMPERATURE.

In many textile operations such as dyeing, scouring and bleaching, a definite temperature must be maintained if uniform results are to be secured. Thus, in wool washing the limits of temperature are narrow and the bowls must not be allowed to cool below the lower limit, otherwise, badly scoured batches will pass forward to the spinning department. In peroxide bleaching, indigo dyeing, etc., proper temperatures must be attained and controlled. To secure this, exact regulation independently of the human factor, apparatus of the thermostat type is occasionally fitted to the plant. Such devices depend on the expansion principle, usually of liquids or gases in a hermetically closed system, this expansion causing a pressure which is used to actuate the valve system. In the Hopkinson Thermostat Control Valve, figured in the text, an intermediate pilot valve is operated by the pressure diaphragm and the main valve controlled from this by a piston. The arrangement secures sensitiveness, i.e., quickness of response, with definite control. The principle and details of construction will be apparent from the explanatory drawing.

POWER IN THE FINISHING DEPARTMENT.

The excessive costs of fuel in post-war years have compelled attention in textile works to economies both of heat and power. It is not intended in a text book of cloth finishing to cover completely the power problems of textile factories, but some knowledge of this side of management is essential to the supervisors and staff. In what follows, the provision of electrical power is mainly considered. The power demands of a finishing plant have special features, in the following respects :— (a) There are many different types of machines in the plant. (6) Most of these—milling, press pumps, etc., excepted—are of moderate power. I (c) Many of them are intermittently worked, stoppages for adjustment, etc., being frequent. (d) Very exact, steady or synchronous driving is not par- ticularly necessary. (¢) There is a great range of speeds, and some must have variable speed. (f) Itis very advantageous to run certain machines overtime or individually, e.g., the Tenter. When these considerations are reviewed, it is seen that the power supply need not be particularly heavy, that it will be I fluctuating, there will be great speed variation and consequently difficulty in assembling the units, and further, it is very desir- able to secure general cleanliness in the driving arrangements.

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If the finishing department is one portion of a complete factory, its power demands will be considered a part of the entire installation, and the question of separate engine or generator, shaft drives, or electric supply will be determined accordingly. In any case, however, it will be found that the power supply for a finishing works is peculiarly fitted for provision by an electrical system. The convenience of location, elimination of overhead shafts and belts, ease of additions or extensions, reliability, economy, low maintenance costs, make electric driving the ideal system for a cloth finishing plant. Whether the electrical energy shall be generated on the spot or taken from the mains of a municipality or power company is a question of circumstances. Generally speaking, if the finishing plant is isolated and the problem is for the providing of power for the finishing machines only, it is best to purchase the energy from a public supply ; capital expenditure is reduced, the supply will be steadier and more reliable, there is practical immunity from breakdown, and in many cases the running cost will be less, even though a boiler for the supply of process steam may be on the works. Small steam engines, in these days of dear fuel, are uneconomical. The writer has known cases where the transmission losses in mills of the older type (the vertical shaft with cross bevels of the Fairbairn design) have amounted to over 40% of the coal bill.

A table of the different machines of a finishing plant is given below, with suitable pulley sizes, speeds and average horse-

powers required :— MACHINE REVS. PER PULLEYS. MINUTE. H,P. Open Washer 24 x 6 ins. 120 + 5-ft. Dolly Washer 30 "8: 5, 90 7 6-ft. Washer Off Sa OG, 90 7 Mangle or Squeezer xa, 120 3 Miller, roller yee 100 8-10 Tenter ; 3B, 12L 16 X45 150-180 4 ‘Tenter, fan See 900 3 Teazle 20° 8, 150 6 Brush Dewer 14 xk 2 240 2 Cutting or Shearing 1D "28, 300 13 Single Brush 18 4 300 3 Rotary Press in € 190 4—6 Blowing (machine) in oe 4 180 2 Blowing (pump) a0 90 10 Rigger and Folder. in te 75 3 Baling Press IO KO 220 7

The more time and thought which can be given to questions of lay-out, grouping, individual drive and similar details, and the better, the final experience of most managers being that

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subsequent working invariably shows up weaknesses in the initial planning. It is now a settled question that the best all-round system of electrical driving is by means of 3-phase alternating current of 50 periods and a voltage of 400. These data are becoming a standard for supply companies in this country, and manufacturers of electric motors stock units of all powers and speeds, such as 940, 720, 480, 375, etc., revolu- tions per minute. In any particular works, the plan of the mill or a rough drawing drafted out is obtained on which the machine positions, the line shafts and the speeds are marked.

Such a plan is necessary, in order :—

(2) To locate the supply points and distribution boxes with switch gear. (6) To arrange the most convenient and economical cable runs. (c) To ascertain the best arrangement of drives, group or individual. (d) To fix the positions of the motors and drives therefrom.

The question which now arises is the number of motors to be installed, i.e., into how many drives the plant shall be subdivided. This problem of grouping v. individual driving depends on two factors, viz., (1) Initial Cost, (2) Running Costs. It can only be settled on the consideration of the special circumstances. A large number of comparatively small motor units makes for heavy first cost, both on the machines them- selves and on their installation. Hence, from the point of view of low initial expenditure, the motors should be as large as possible. To take a numerical example, an installation of ten 5-h.p. 960 r.p.m. squirrel cage motors at £5 2s. Od. per h.p. would cost £260; two 25-h.p. 960 r.p.m. squirrel cage motors at £3 10s. per h.p. would cost £175; and a single 50-h.p. motor at £2 15s. per h.p. would only cost £137 10s. Coming to the factor of running costs, it is evident that an increased initial expenditure resulting in a small percentage saving in running expenses is very soon offset by these diminished running costs, the reason being that while the first cost is stationary the running charges carry on year after year, and are thus cumulative over a period of time. If, for example, the running costs of the installation were diminished by 5%, the total saving in ten years would be 50% of the initial expenditure on the plant installed. The basis of the whole question depends upon the following points :—

(a) Will the machines to be driven run constantly throughout the working day, or are they intermittent ? (5) Is the existing method of driving efficient ; or can it be made more efficient by splitting it up into several units ?

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df

In order to illustrate these points, consider a mill of six floors driven by a vertical shaft and cross bevels to the line shaft on each floor. It would be possible to drive the upright shaft by a single big motor, but it is very much better to instal a separate motor on each floor to each line shaft. Take again

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44

the common case where several heavy shafts are driven by ropes from one to the other, some of the shafts often being mere intermediates, carrying no machines themselves. It is nearly always better to make these shafts into separate motor drives. Further, where very great steadiness of running is necessary it is found that the distant machines are more uneven in speed variation, owing to the torsion of the shafts and the slip of belts and ropes. In this case, subdivision is required and motor units installed. It must be remembered that in general the efficiency and power factor of electric motors is higher as the size of the motor increases with a given speed, but on the other hand a large motor driving a group of machines and operating under full load when some of the machines are off duty, loses rapidly in efficiency. Also, if rearrangements are desired, this is a simple affair when the machines are individually driven, but if they are grouped it usually means that a motor is either over-loaded or under its rating, both of which are undesirable conditions.

Another important point, and usually the most difficult, is the actual horsepower of the motors to be installed for the various drives. The correct rating must be found, because :—

(a) The efficiency of a motor is highest at its full load and diminishes as the load falls. (5) In most cases the charge for current is based on kilo- volt-amperes (K.V.A.), therefore the power factor of the motor must be as high as possible.

The following illustration shows the effect of the power factor on the running costs :—

For the typical installation with power charges of 8/— per k.v.a. per month of maximum demand, plus 0.5d. per unit. If the power factor of the installation were 0.85, the total running costs would be about, per year, £3,900. If the power factor were 0.6, the total running costs per year would be about £4,800. Showing a saving in a year’s running costs, due to an increase in power factor from 0.6 to 0.85, of approximately £900.

The following example shows the savings which may be effected by an increase in efficiency :— For the same typical installation of the figure with power charged at a flat rate of 1d. per unit. If the motors had an overall efficiency of 90%, the annual running costs would be approximately £3,700. If the overall efficiency were only 70%, £4,750. Hence an increase of efficiency of from 70 to 90% would result in an annual saving of approximately £1,050.

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There are many complications, however, in that many drives take widely varying powers, owing to intermittent running of machines, machines standing, and in some cases machines being loaded differently at different times. Also, there are cases where different classes of materials are manu- factured at one time or another, with the consequent varying load. These variable factors are very characteristic of a finishing plant. A diversity or load factor must therefore be assumed in each case, i.e., a mean load for each drive; this varies in most mills, but can usually be taken as round about 1.2 to 1.5. It will be wider on a purely finishing plant. Fortunately, motors of reputable make have an overload capacity which is standardised at 25% for two hours, 50% for half-an-hour, and 100°, momentarily; this can be taken advantage of, as in many instances the heavier loads only obtain tor a limited period, and the overload capacity of the motors may be utilised to carry the peaks. Alternating current 3-phase induction motors can be obtained in two types :— (1) Fitted with slip-rings mostly used in large sizes for starting under heavy loads. . (2) The squirrel cage type, where there are no sliding electrical contacts at all. Without doubt, the squirrel cage motor will be used wherever possible rather than the slip-ring, on account of its lower first cost, its greater simplicity and the less complexity of the control gear. In many cases it is necessary to use the slip- ring motor for the following reasons :—The starting torque is greater than that of the squirrel cage motor, and if the high starting torque is necessary (i.e., where there are direct drive and no clutches or fast and loose pulleys) the slip-ring motor must be used. Further, owing to the large initial current taken by the squirrel cage type, the supply company usually fixes a limit to the size of motors of this kind permissible on the mains. In these days it is becoming common to fit some form of centrifugal clutch, so that the motor may get up full speed before taking on the drive. Motors are built with several types of enclosures, i.e. :— (a) Open Protected Type, giving free ventilation. (6) Enclosed Ventilated Type, similar to above, but with wire gauze or expanded metal over the openings to exclude flock, etc. (c) Pipe Ventilated Type. These are totally enclosed, except for one inlet and one outlet flange, and have an internal fan to draw air through the motor. Ducts or pipes are fitted to carry cool or clean air to the motor. (d) Totally Enclosed Motor. No openings, but the heat is dissipated by conduction through the carcase of the motor,

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In finishing rooms, there must be exclusion of flocks and moisture, and the enclosed or pipe ventilated kinds are often used. The motors may be direct-coupled to the machines or shafts, or there may be belts, ropes, chains or gears as connections. The points which determine the nature of the connection are the shaft speed, the available space and nature of the surround- ings and the size of the motor. In electric motors, the prime cost decreases with increase of speed, due to the dimensions of the motor being relatively smaller, and the power factor is greater in the higher-speed machines. But shaft speeds are often low in textile drives, and double reduction belt or gear drives are expensive ; hence, low-speed motors cannot always be avoided. Again, a cramped space may necessitate a chain or gear drive, or a bad atmosphere in bleaching or carbonising may prevent a belt drive functioning well. Belt drives are, in general, cheapest, will allow some end play, and the slip prevents shocks; the usual pulley ratios range not greater than 4 or 5 to 1, preferably the former. Only on larger pulleys can rope drives be successfully used. The drive by gearing is useful when the shaft or machine runs at a low speed, e.g., press pumps. Chain drives are becoming increasingly popular where short driving centres are entailed and the speed ratio between driver and driven is not more than, say, 6 to 1; rigid supports and perfect alignment are essential. In certain cases, helical gearing makes an efficient but somewhat expensive drive. It is not often in finishing machinery that direct coupling of the motor on the machine shaft can be resorted to, but occasionally a clutch makes this possible.

A few typical cases may now be discussed as illustrations. Taking first the milling shed, with a line shaft running at 90 to 100 r.p.m. This might be arranged by :—

(a) Gear drive from a 960 r.p.m. motor. (6) Double reduction belt drive from a 960 r.p.m. motor. (c) Speed up the line shaft to 180 r.p.m. and drive through a belt from a 720 r.p.m. motor. (d) Pair two milling machines on one motor with a chain drive to large sprocket wheels on their shafts.

The first arrangement is very efficient, but would be costly for gearing and millwrighting. The second is reasonably efficient, but requires space, while the third is cheapest and fairly compact and efficient. The fourth is a good job, but costly. Scouring plant for pieces may be similarly treated. In the tentering room, it would ordinarily be practicable to couple the motor directly on the fan shatt and take the com- paratively low-power tenter drive by reduction from this. Shearing machines, with fairly high speeds but very low power,

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are best grouped on a single line shaft. The blowing machines can run from a shaft at 180, and the exhaust pump also by half reduction from the same shaft. Hydraulic presses must have double reduction gearing to get the requisite low speed

and power.

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The usual systems of laying cables and wiring are :-— (a) Paper Insulated, or (6) Vulcanised India Rubber Insulated. The former is always lead-covered and the latter may be armoured ; if unarmoured it would be run in steel conduit. These lead to four alternative methods of wiring :—

1. V.I.R. Cable run in conduit. 2. V.1.R. Cable armoured clipped to the walls. 3. Paper Insulated, plain lead-covered, run in cleats on

cable racks. 4. Paper Insulated armoured clipped to the walls.

The cheapest for the smaller cables is to run V.L.R. Cable in conduit; for main cables to distribution boxes or large

motors, the cheapest is Paper Insulated Cable.

Page 73

WooL AND CHEMICAL REAGENTS.

Page 75

CHAPTER II.

Wool and Chemical Reagents ; Acids, Alkalies and Salts.

It is of the utmost technical importance to determine the chemical behaviour of wool towards the principal acids, alkalies, and salts. The extended use of acids in dyeing, carbonisation, bleaching, and acid-milling, and the equally extended employment of alkalies, separately and in soaps, for wool-washing and piece-scouring, require an intimate know- ledge of their reactions on the fibre. Curiously enough, this particular subject is by no means explored or defined in a degree tantamount to its importance, the reason largely being the ill-understood chemical nature of the wool fibre itself. (See Section on Fibre Chemistry). All experimenters agree as to the absorptive power of wool substance for various reagents and its strong retentive powers. In the particular case of Sulphuric Acid and Wool, the results are divergent and further work, under more restricted and comparable conditions, especially as regards raw material, is desirable. Similarly un- reconciled statements exist with regard to the influence on tensile strength of certain alkalies, mordants, etc.

Wool and Sulphuric Acid.

This particular case has received much attention, being of course of wide technical application. In the ‘‘ Manual of Dyeing ”’ (Knecht and others), p. 40, it is correctly stated that dilute acids have little effect on wool; concentrated acids destroy and dissolve it, especially at higher temperatures. A table by Furstenhagen and Appleyard of the absorption of sulphuric acid by wool from various concentrations is quoted, and it is asserted that ‘“‘ a not inconsiderable portion appears to be permanently absorbed or neutralised by the fibre.’’ This conclusion seems to have been generally confirmed by other observers. Lloyd (Jour. Soc. Dyers & Cols., 1912, p. 339) finds that acid was retained after twelve extractions with boiling

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water. Fort and Lloyd (1914, p. 5) state that acid was permanently retained against three cold water washings together with 100 c.c. of boiling water for fifteen minutes, three times repeated. Their curve of absorption showed nodes, which it was claimed represented definite compounds of wool and H,SO,, due to additive salt formation. They noted that in their titrations some opalescence appeared on neutralisation due to dissolved wool substance. In the same journal (1915, p. 81), Messrs. Fort and Swares say “ that combination of acids with wool is not a simple function of the basicity of acids, but is due to addition as in the case of aniline salts.”” And Fort and Anderson (1915, p. 96) found variations in absorption with different kinds of wool, and again conclude that there is chemical union of acid and wool. Messrs. Fort and Pearson (p. 222) state: “The complex nature of wool is the great obstacle to a complete understanding of what takes place, inasmuch as the hydrolytic changes cannot be followed, nor the number and kind of basic bodies actually combining, isolated or estimated, . . . . wool boiled with sulphuric acid and then extracted with water to remove loose acid will release further amounts of sulphuric acid on dyeing with a colour acid. While some of the acid is free, as shown by the qualitative tests, we have not found it all to be free; . .. .,such basic matter as the acid combines with must, of course, come from the wool.” W. Harrison (Jour. Soc. Dyers & Cols., 1918, p. 57) found that the acid absorbed from a 4.9% solution on the weight of the wool could be completely removed ; twenty-four extractions by boiling water showed that no measurable amount was retained. Woodmansey (the same journal, 1918, p. 172) states that ‘‘ it appears tedious and impracticable to determine acidity by the washing out method; ... . , if when cloth is immersed in water the resulting solution be not acid to a sensitive indicator, it may be concluded with some justification that the material is non-acid.’”’ But quoting a contrary experiment, he says: ‘‘ We may assume that apparently neutral cloth can still contain sufficient acid to yield a minute trace to a substance in contact and capable of absorbing Gelmo and Suida, in 1906, had noted that on treating wool with H,SO,, long continued washing with water does not remove the whole of the acid; after all traces have disappeared from the wash- water, dilute Ammonium Carbonate will remove a further quantity. Hence it appears likely that there is stable com- bination between wool and acid, and not mere absorption. This strong retention of once-absorbed—perhaps adsorbed, and perhaps chemically united—matter is noticed with other colloids. Whether in the case of wool it is permanent against water extractions, must be further investigated. If, after treatment with sulphuric acid, neutrality is to be obtained on

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wool, in practice alkalies are used. The technical importance of the above researches is the necessity of thorough neutralisa- tion ; it is obvious that a sort of latent acidity may exist, ready for development under new conditions. On the whole, it appears probable that the action of wool with sulphuric acid is a chemical union. lL. Vignon found in this, as in other cases, a distinct heat of reaction; a test which has been usually regarded as crucial in this respect.

THE ABSORPTION OF ACIDS BY WOOL

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The problem of the reactions of wool—or rather Keratin— with acids, alkalies, and chemical reagents generally, should be considered in the light of the general protein reactions of similar type. Erroneous conclusions have undoubtedly been drawn, owing to an unduly narrowed outlook in such researches. In the case of Sulphuric Acid, a mere absorptive view of the reaction appears to have been the prevailing standpoint, almost exclusive of the possibility of chemical combination.

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‘FT “DIA

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Yet in other proteins such combination is indisputable. Hence the controversy regarding the permanent retention of acids, etc., by wool has been largely one-sided. In the case where sulphuric acid is said to have been totally removed by twenty-

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four extractions with boiling water, there does not seem to have been any investigation—beyond titrations—as to whether these washings were bringing any other constituents away, e.g., products of hydrolysis or ‘‘ wool gelatine.”? The balance of evidence appears to be that Keratin or wool substance forms real compounds with acids. I

Again, the use of indicators is liable to result in fallacies when applied indiscriminately to colloid and especially protein solutions ; it has been extensively employed just as in ordinary acidimetry and alkalimetry, without regard to its limitations. Many of the usual indicators combine with or are adsorbed by the colloid, and the indicator thus disturbs the equilibrium it is designed to reveal. T. Brailsford Robertson, in “‘ The Physical Chemistry of the Proteins,’’ says :—

** Owing to the amphoteric character of the proteins, and also to their multiple combining capacities, the changes in the hydrogen or hydroxyl-ion content of protein solutions, upon the addition of acid or alkali, over a considerable range, are relatively slight, and for this reason sharp end-reactions are rarely obtained with indicators in protein solutions, unless their colour changes occur at H— or OH- concentrations lying without or upon the boundaries of this range.”

An interesting property of proteins bearing upon the use of acids in the dyebath, etc., is illustrated in the following excerpt from Robertson :—

order that a protein may react with an acid which is insufficiently dissociated to break up its -N.HOC- groups, some stronger acid must be present, combined with the protein, and which can then be displaced by the weaker acid through the agency of one of its more strongly ionised salts. Hence it is observed that proteins will com- bine with very weak acids or with the acid radical of salts more readily in acid than in neutral or alkaline solution, and with very weak bases or the basic radical of salts in an alkaline rather than a neutral or acid medium. Similarly, a protein may not be able to decompose a salt of an acid, binding the acid (or base as the case may be), but, in the presence of a free acid it may be able to do so, partly because the first acid is partially set free from its salt by the second, but also because the ionisation of the protein is increased.”’

Microscopic examination of wool after the action of acids and alkalies by Seel and Sander (Zeit. angew. Chem., 1916, p. 29), with a magnification of 700-1000, showed that 1% sulphuric acid boiling for one hour, did not damage or modify the wool in this respect. The action of concentrated acid upon wool fibre enters into the process of carbonisation of the vegetable matter of raw wool. The material is steeped in approximately 5° sulphuric acid, then dried out at a tempera- ture not exceeding 50°-60°C.; a subsequent heating to 80°, 90°, or even 100°C. for a short time being given in the “ baking ”’ stage ; the total process varying from 14-6 hours or more. The purely vegetable tissues are charred as the acid strength

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increases in the drying and baking. It is certain that the wool is also adversely affected, though relatively much less than the burrs, etc. ; but there is some loss of shade and diminution in tensile strength.

EFFECT OF ACID UPON STRENGTH.

A series of experiments on the influence of Sulphuric Acid upon tensile strength were carried out by W. Harrison, for the Wool Research Association, in 1919, the general results of which were as follows :— The results of previous observers upon action in the cold were confirmed ; acid up to 80% strength had little effect at the lower temperatures, i.e., below 50°C. ; impregnation by strong acids itself produces heat and consequent tendering; nor was the effect of long immersion very marked. On the other hand, with strong acid of 80% or over, and at higher temperatures than about 50°C., tendering occurred. When wool was boiled with solutions of more than 10% on the weight of the wool—or about 0.33% in the solution— tendering commenced ; the pronounced effect of temperature was shown in an experiment with acid of 16.5% strength, 500 times the weight of the yarn, warmed at 50°C. for one hour without appreciable tendering. Generally, wool was likely to be damaged by sulphuric acid at all temperatures above 60°C. (140°F.).

The bearing of the results on the technics of the industry as far as regards carbonising, for example, is to confirm the strength of 5%, which is probably about average practice ; also, the drying stage should be conducted at as low a tempera- ture as possible, not more than 50°C. In dyeing, the well- founded opinion that boilings in acids, especially long-continued, are prejudicial to the fibre-strength, is supported by these facts.

EFFECT OF WOOL BLEACHING.

Sulphurous Acid may produce tendering in union goods when the washing processes are imperfectly conducted. The ordinary stoving process of bleaching wool—by the burning of sulphur in closed chambers and exposure to the fumes—has numerous secondary effects not well recognised in practice. Some few per cents. of Sulphur Trioxide, SO,, are formed at the same time, and this with the moisture present forms sulphuric acid in the fabric. Concentration during drying, e.g., in the tentering, may deteriorate the cotton elements of the cloth accordingly. Sulphuric acid may be demonstrated even in flour of sulphur by extraction with water and the Barium Chloride test; it is similarly revealed in sulphurous acid solutions or extraction of stoved fabrics.

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The other acids of textile interest—hydrochloric, nitric, acetic, formic, tartaric, etc.—are mainly important to the, dyer, and will not be noticed here.

EFFECT OF HEAT ON WOOL.

The loss of water on heating is accompanied by an increase in the tensile strength which is lost on exposure to the air and reconditioning. Wetting out gives an increased elongation prior to rupture, pointing to a kind of gelatinisation effect (turgescence). The loss of strength from prolonged boiling is greater, and is a permanent deterioration ; dry heat is not so destructive. Scorched or overheated wool is less absorptive than ordinary wool. In heated wool the combined sulphur becomes oxidised, and a double action may occur ; this sulphur acidity may fix the ammonia, which is always liberated at high temperatures from wool. (Woodmansey.) A further example of deceptive strength tests is afforded by the subjoined trial :— A worsted cloth, 60’s quality, 14 ozs. weight, twofold twist warp and weft, was tested before carbonisation. It was then tested after one carbonisation, and after two carbonisations, in the ordinary commercial way. A large number of tests were made—about 100 in all—with the following results :— Uncarbonised, 77.2 lbs. breaking load ; stretch 2.3 ins. Carbonised once, 76.9 lbs. Be ies ie ke Carbonised twice, 76.8 lbs. J cae SO: Apparently the carbonisation has strengthened the cloth ; but the cloth shrank 5% in the aa hence 5°% more threads were in the test piece.

Alkalies :—-Potash, Soda and Ammonia.

Alkalies, including in this term the hydroxides and the carbonates of potassium, sodium and ammonium, are applied in cloth finishing almost entirely as detergents themselves, or as components of soaps. As separate detergents, the carbonates are principally employed, the hydroxides in any but the lowest concentrations exerting a caustic action on wool, a property shared by certain other alkaline salts, e.g., sodium sulphide. The consideration of alkalies in wool or piece scouring is practically limited at the present time to compounds of sodium and ammonium. The corresponding compounds of potassium, viz., Caustic Potash and Carbonate of Potash (pearlash), were almost eliminated by the war and the operation of the German monopoly. The use of potash soaps is discussed in another section. It is possible that the former preferences for potash detergents will never hold the same sway.

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58 AMMONIA.

Ammonia is still largely used as a normal agent in the scour in many works; it is questionable, as in the case of potash, whether its employment is not greatly traditional, dating from the early use of urine containing ammonium carbonate, as a scour. I

Ammonia as saturated solution, specific gravity 0.880, containing about 35% by weight of the gas, does not come into the works. The ordinary ammonia liquor of 16°Beaumé has about 9.9% by weight, 0.960 specific gravity, 21.8% of ammonia gas. From these data, the comparison of the actual weight of alkali added to a scour in one form or another can be made. Thus a gallon of 0.920 s.g. weighing about 9 lbs. would add to a scour approximately one-fifth of this weight ; that is, a little short of 2 lbs. of actual ammonia to be used in the saponification of fatty acid, etc. The chemistry of ammonia soaps is discussed in the chapter on Soaps.

In spite of its heavy cost as compared with soda ash, is a wide-spread opinion among practical scourers in favour of ammonia as a detergent alkali. If the scouring efficiency were measured by the relative alkalinity only, by the power of forming soap with the fatty acids of the wool oils, then this is purchased by the employment of ammonia liquor at ten or twelve times the cost of using ordinary soda ash. But the real question is probably much more complex and not yet thoroughly worked out. The alkali of ammonia is in the form of hydroxide, as against carbonate in the soda ash; if the judicious use of caustic soda were more general in scouring sheds, it is possible that ammonia might not be so advantageous. Again, ordinary ammonia will effect immediate saponification of the oleic acids of the wool oils at the common temperatures, i.e., there is a formation of ammonia soap by the cold process. This is not the result, or in very much lessened degree, when carbonated alkali is used. It may be that in the scouring process there is a good deal of emulsification preceded by relatively little true saponification ; that is to say, a small chemical followed by a comparatively large physical effect. If this is the real position, the advantages of a quick initial soap formation may be very great and substances such as ammonia which promote this will be correspondingly useful. In addition to the factor of caustic as against carbonated alkali, the property of volatility in the ammonia must be noted ; ammonia liquor of itself leaves no residue of solid salts in the fibre. The ammonia soap formed, i.e., Ammonia Oleate, is highly soluble, readily forms a colloidal solution at ordinary temperatures, is not subject to ‘“‘ salting out’’ by excess of alkali, and is a powerful basis for emulsification.

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There have been numerous trade detergents, sold under impressive names derived from the classical languages, com- pounded of ammonia and crude oleic acids—that is, based on an ammonia soap—and having some added solvent body, e.g., Tetrachlorethane, Carbon Tetrachloride, etc. Such mixtures have remarkable emulsifying powers, and can be of great service to the scourer in special cases. For everyday use, their cost is prohibitive, and further, they can be prepared without difficulty on the spot from ammonia liquor and a good quality soap olein, adding the special solvent in quantity capable of being carried permanently in the emulsion.

The methods of physical chemistry applied to the dissociation of acids and bases show that ammonia—contrary to the older chemical view—is comparatively a weak base. (See section on Theory of Chemical Actions in Solutions). The cause of basicity is the presence of Hydroxyl (OH), ions, the basic property is present in proportion to the number of such ions, i.e., to the dissociation. Now the really strong bases, the hydroxides of the alkali metals, sodium, potassium, calcium, etc., are dissociated, for similar concentrations, to about the same extent as the stronger mineral acids. But ammonia hydroxide is very much weaker, in fact at high dilution. only about one-eighth as strong as caustic potash. Some con- troversy exists in chemical circles upon the exact constitution of solutions of ammonium hydroxide.

Solin Compounds.

Of these, the principal are Caustic Soda or Sodium Hydroxide, Sodium Carbonate, Sodium Sulphate, Sodium Chloride, Sodium Bisulphite. This last is used as a bleach. The sulphate and chloride (common salt) are used in staining, and as restrainers against the bleeding-off of dyes from the fibre.

CAUSTIC SODA.

This is rarely used as a scouring agent on wool or animal fibres, but extensively so on cotton and vegetable fibres. It is marketed as the solid salt, 98%, and should be purchased for the scouring shed in that form for economy of transport ; but other qualities 78/79°, 76/77°, 70/72°, and 60/62°, where the degree represents very nearly the percentage of sodium oxide, Na,O, are obtainable. A liquid form of 90° or 100°Tw. is also supplied. Caustic soda acts strongly on wool in quite small concentrations, especially at temperatures greater than normal. Harrison states that “appreciable tendering is produced at 50°C. in one hour by a 0.04% solution ; even at 20°C. anything

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above 1% deteriorates the fibre.’”” It seems to be established that caustic potash and caustic soda have a direct chemical action upon the wool (see Vignon’s thermal experiments), removing sulphur from the molecule, and dissolving the fibre. The wool becomes brown, a quite general phenomenon with alkaline substances. Several observers, Knecht, Buntrock, Washburn, etc., have experimented on the action of caustic soda solutions on wool. It is found that at higher concentrations the wool substance does not suffer the disintegration caused by heat at even low strengths. Buntrock found that solutions of caustic soda of 5-70°Tw.—say up to 30% —dissolved the fibre, but from this up to 100°Tw. (47%), a pseudo mercerisation takes place ; the tensile strength was increased and a silky lustre and scroop acquired. Matthews (Jour. Soc. Chem. Ind., 1902, p. 685), working on 2/26 worsted yarn in hanks of forty threads, gives the following table :— .

DENSITY OF TENSILE REMARKS NaHO. STRENGTH. Tw. 41.3 5 39.4 Yarn yellow, harsh, 25 27.8 brittle, felted. 35 Yarn dissolved. Solution yellow. 40 Formed a shining mass. 60 25.3 Yarn much felted and yellow. 70 30.5 Felted, yellowish. 75 39.5 Lustrous and silky. 80 56.5 Yarn white, lustrous, 85 52.4 silky, and having 90 46.5 Scroop. 100 37 Yarn, brittle, yellow, and harsh.

The yarn was immersed for five minutes at 18°C., immediately washed with water, and then in 1°% sulphuric acid at 60—70°C. The temperature and time of immersion are important ; coarse yarns benefit most. The yarn must be well scoured and wetted before entering the bath of caustic soda. Up to 80% of the natural sulphur of the wool is removed in the process. The initial loss of strength, the regain, and the surface effects given above are confirmed by other workers ; no technical application, however, appears to have developed therefrom. Seel and Sander, by a microscopic examination noted that a 1% solution of caustic soda acting for fifteen minutes, causes wrinkling of the epithelial scales, resulting in longitudinal striations, and later in pronounced furrows. Disintegration of the epidermal layer commences at 70°C. and at 80°C. the cuticle and the fibre layer are completely separated.

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In view of recent developments in treating proteid substances by caustic soda with the object of preparing detergents, it may be noted that Paal (Berl. Ber., 1902, p. 2195), obtained two products by the action of NaHO on egg albumin ;_ one thrown out of solution by acids—Protalbinic Acid—the other Lysal- binic Acid. Protalbinic acid froths strongly in alkaline solutions.

Becke, using the biuret reaction on proteids to detect and estimate changes in wool dissolved by hydrolysis, concluded that :—

1. Caustic alkalies and alkaline carbonates dissolve the fibre in a degree proportional to their concentration, and the destructive effect increases with the temperature. 2. Neutral soap solutions practically do not dissolve wool. In the hydrolysis of wool the alkalies remove sulphur.

CAUSTIC SODA IN THE SCOUR.

The possible use of caustic soda is certainly a question for further research in wool or piece scouring. The production of a slight amount of Sodium Hydrate by soap dissociation in the scour has already been noted in treating of the hydrolysis of soaps (see Chap. VI). Some discussion of alkaline dissociations is given in a paper by Farrell and Goldsmith, on the “‘ Action of Detergents on Cotton and Linen ”’ (Jour. Soc. Dyers & Cols., 1910, p. 195), from the point of view of the ionisation theory. 0.2% of Sodium Hydrate is dissociated to the extent of 80% at 18°C., and therefore contains 0.08% Hydroxyl or OH ions. A 5% solution of Sodium Carbonate is dissociated to the extent of 40°% of the salt molecules. The authors state that a dilute solution of Sodium Carbonate exists as :— 2Na + CO, + H + OH = NaHCO, + Na + OH that is, Sodium Bicarbonate and Caustic Soda are present. sodium carbonate solution is dissociated as above, and contains 0.01% of caustic soda ionised. It is evident that the detergent actions of Caustic soda, NaHO, and Sodium carbonate Na,CO,, are different. Nearly all the theoretical OH ions of caustic soda solution are immediately available for detergent action ; but in the case of sodium carbonate, these negative OH ions, the primary detergent agents, are largely in reserve. On heating the solution, there is an increase of dissociation. Thus sodium carbonate, Na,CO,, solution presents a case of automatically regulated dissociation and hydrolysis. Sodium Hydrate, NaHO, reacts at once even in cold solutions.

If fabrics are immersed in such solutions, the negative Hydroxyl ions combine with the fat and certain other elements

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of the dirt chemically ; further dissociations take place, and a repetition of these interactions. Thus with Sodium Carbonate the supply of active detergent ions is in a sense automatically equilibrated. A Caustic Soda solution is immediately active in consequence of its greater dissociation.

It must be remembered that the strength of ordinary scouring baths in alkali, soap, etc.,issmall. Sodium Carbonate strengths should not usually exceed 3-4°%% and soap scours are still less concentrated. The actual concentration of caustic soda from hydrolysis alkali is obviously very small ; even the presence of free caustic as excess alkali from the manufacturing process would not ordinarily bring it up to a dangerous stage. Again, ordinary scouring is generally carried on at temperatures not exceeding 100°F., or say 40°C., and often much less. It is possible, therefore, that small additions of caustic soda might be made to a scour without damage ; but careful control will be necessary. I

Caustic Soda is known to remove part of the combined sulphur of the wool ; lime water has been used for this purpose. Schneider remarks: that wool treated in this way has its reducing properties on chromium mordants increased, and _recommends boiling for 15 minutes with a 0.05% solution (See Harrison’s results, re tendering.—ED.), and rinsing off with an equivalent quantity of sulphuric acid.

NOTE ON TENSILE TESTS AND ACTION OF REAGENTS.

It is perhaps scarcely legitimate, as is the case in many experimental researches on chemical actions on wool, to make tensile tests on YARNS and assume that these will then apply quantitatively to WOOL. Where, as in the case of Caustic Soda, there is evidently a minimum tensile strength at some particular concentration, it is hardly likely that this turning- point would be the same when determined from yarns as when got from tests on actual fibres. An engineer would not carry out a series of stress and strain experiments on stranded wires and put forward the results as the standard constants of the material ; yarns are to individual fibres of wool what stranded cable is to the single wires. The physicist has experimental means of determining the physical constants of fine filaments (Cf. Prof. Boys on Quartz Fibres). It is certain that many discrepancies would be cleared up if this source of error were recognised. Mere steeping of a yarn sample in cold water and drying out, alters the lie of the individual fibres, and therefore the internal friction and the tensile strength, and any mechani- cal displacement much more so.’ The fact that yarn is the unit of fabric structure does not mark it out as the proper raw

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material on which to elucidate the chemical reactions of wool as far as they affect its general mechanical properties. It is now a well-known fact that yarn is a material in a state of mechanical strain. The storing for seasoning and the steaming process are practical recognitions of this fact. Yarn, like stressed metals, shows the phenomenon of “ elastiche nach- wirkung,”’ i.e., elastic after-working, a pseudo annealing effect in which the material accommodates itself. Any process such as steeping in liquids, even without direct chemical action, facilitates the release of strains.

Sodium Carbonate.

This most important detergent is variously known as Soda ; Soda-ash ; Alkali; it is supplied also as Soda Crystals or Washing-soda, Na,CO,, 10 H,O. The Bicarbonate of Soda is NaHCO,. The common Brunner-Mond alkali of the scouring shed is soda-ash containing 58° Sodium Oxide, Na,O, or over 95% pure Sodium Carbonate, Na,CO,, anhydrous. Small quantities of bicarbonate and caustic soda, and less of common salt are present in the commerical article, along with some moisture. A table of its properties, as far as they are involved in the ordinary scouring applications, is appended.

SODA-ASH TABLE.

SOLU- PER ENTN. TW. SPECIFIC TEMPERATURE. _ BILITY. SODA. DEGREE. GRAVITY. 5° Cent. 9.5% 0.95 1.01 15 16.4 1.90 4 1.02 25 28 .2 2.85 6 1.03 32.5 46.2 Bede od 1.035 40 46.1 4.76 10 1.05 100 45.5 5.71 12 1.06 105 45.2 9.43 20 40

It will be noted that the solubility increases with the temperature to a maximum at about 32.5°C. or 90°F.; there is then a concentration of about 46%. Thus both the solubility and the temperature factors indicate practical limits to the strength of the alkali scour. If the dirt and grease of a fabric require more alkali, it should be applied by increasing the quantity of solution rather than by strengthening the concentration. Sodium Carbonate is used in enormous quantities in the textile trades. The wool carboniser employs it for after neutralisation, and it.is the mainstay of the wool and piece scourer. Its action on wool in dilute solutions and at moderate

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temperatures is inappreciable. Harrison states that, using 5% for an hour, not beyond 50°C. (122°F.), wool was not tendered.

ALKALI-STRENGTH.

The proper strength of alkali for scouring is another disputed question in works practice. It has been touched upon to some extent in connection with the parallel question of soap strength, but it is necessary to treat it independently. The strength of alkali in the scour must obviously vary with the kind of goods, the amount and nature of the oiling carried by them, and the particular mode of scouring. As already indicated, if the fabrics are heavily oiled—say, 10°%—by a lubricant containing - considerable fatty acid, the first scour should be -by alkali alone ; in this case a strength of 6—7°Tw.—about 3% concen- tration of sodium carbonate—is a convenient working solution. On the other hand, if the goods are only lightly lubricated— worsteds with a fairly neutral oil—the scour might be of a combined alkali and soap type, and a smaller concentration, 24°Tw., will be found workable. Some element of judgment must always be used by the operatives, and an average solution adapted to meet most conditions is the best.course to follow,

MAKING-UP ALKALI SOLUTIONS.

It is undoubtedly the best practice to make up alkali solutions direct, i.e., without unnecessary weighings or the use of the Twaddell or other hydrometers. This latter instrument usually has its textile working range in quite a short length of stem, it is easily mis-read, is fragile, and subject to temperature error ; it should be put out of use in the scouring shed, except for checking. purposes. The proper course is to have the alkali tank sufficiently large to take the ordinary 2 cwt. bag direct ; a calculation for such a solution to yield 6—7°Tw. from 2 cwts. of soda is here given. N.B.—The practice of tipping the entire sack into the tank should be discouraged ; it is likely to be productive of a crop of burls from the sack fabric to be milled into the pieces at a later stage. 7°T'w. sodium carbonate is a 3.33% solution of Na,COsg, from table. Therefore 100 lbs. solution contains 34 lbs. soda. Now 2 ewts. is 225 lbs., nearly, and therefore :— Number of (100 lbs.) solution required is 225 divided by 10/3 or 6750 lbs. water, or, since 1 gallon weighs 10 lbs., 675 gallons.

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At 624 lbs. to the cubic foot, the capacity necessary is 6750/62 which equals 108 cu. ft. approximately.

Assuming a rectangular cistern, then 108 = length x breadth x depth. Hence tanks of 5 by 5 by 5 ft. = 125 cu. ft.; or 6 by 4 by 5 ft. = 120 cu. ft. will be suitable, allowing some slight margin for overflow.

The tank should be fitted with an inch steam pipe; cold water is run in to say 12 inches deep, the steam turned on, and the alkali tipped in from the sack and dissolved up; cold water is then added to the required volume and the temperature adjusted. Where alkali is piped on to the scouring machines, a gauge glass should be fitted to the alkali tank to secure uniform working.

By WATER STEAM 3

' U i eek i, ! oti ‘ GAUCE 3 i I 120 CUBIC FEET ; 750 GALLONS i! 5 tt i! : ' 1 Ri bin uaa do wot! shige aaa i ‘ - andl ae gen re ie bx ua ot : Y ee en 5. 6' Sn hae oe geile”

Fie 15.—STANDARD ALKALI TANK.

The Theory of Chemical Action in Solutions,

Modern chemistry has proved that substances dissolved in water split up therein to an extent depending on the dilution, temperature, etc., into IONS; thus a common salt, sodium chloride, Na Cl solution contains Sodium and Chlorine atoms in a dissociated state. Such ions are electrically charged ; in this case, the Na ions are positive, (+), and the Cl ions are negative, (—). Caustic Soda solution contains + Na ions and — OH ions. These latter, the Hydroxyl ions, are the cause of the alkaline reaction, which is one of the principal detergent factors. The present considerations, forming the elements of the lonisation Theory, may be applied to the principles of

scouring. E

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This dissociation is a general consequence of the solution of all the chemical substances known as electrolytes, i.e., bodies capable of carrying the electric current when dissolved ; indeed, their conducting power is a result of the ionising process. Thus acids, alkalies, and most metallic salts are electrolytes. The degree of dissociation of a_ particular substance varies with its chemical nature and with the con- centration in the solvent, and also with the temperature and nature of the solvent in question. Taking water as our familiar electrolyte, this in its purest form—specially prepared free from contamination by the containing vessels and by dissolved gases—is not a good electrolyte, the molecules of H,O being only slightly dissociated to the extent of one part in ten millions. Free hydrogen ions (H), and free Hydroxyl (OH) ions exist in the equal concentrations of 1/107; or, in the mathematician’s index notation :— Gi) == (OH) = Thus ten million litres of water contain only one gram of hydrions (H), and 17 grams of hydroxyl ions (OH). In this pure water, the acidity due to the hydrogen ions is equal to the alkalinity due to the hydroxyl ions, and pure water is taken as the standard or datum of absolute neutrality. Hence the concentration of the ions in pure water may be

expressed as :— Cr = Con = 10-7

and this would mean that in one litre of pure water there would be one ten-millionth of a gram of ionised hydrogen or hydroxyl. In order to avoid the use of negative indices and to simplify the mathematics of the physical chemistry of solutions, these data are converted into the logarithms of the reciprocals of the numbers and are then termed the P,, values. Hence, again in the case of pure water, we have :— Py = log. 1 c= log. : Fa ay

Cy 10-7 and thus finally a Pg value of 7 represents neutrality. Values below 7 ranging to zero indicate increasing acidity, and above 7, alkalinity. A decinormal hydrochloric acid solution has a Py number slightly over unity and is strongly acid in reaction ; decinormal caustic soda has a value about 13. The acid or alkaline reaction of solutions of chemically neutral salts such as potassium cyanide, sodium carbonate, etc., is quantitatively related to the dissociation constants of the weak acid or alkali. A solution of potassium cyanide contains free alkali and smells of hydrocyanic acid. The above considerations have an immediate application in the employment of indicators as revealers of acidity, alkalinity, or neutrality. The old-fashioned Litmus solution changed from red to blue at P,, 5-8, about the region of neutrality.

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But other indicators differ not only in their range of colour change, but also location. Phenol Phthalein, for example, changes from colourless to red at Py 8.3-10, entirely within the region of alkalinity; and Methyl Orange, from red to yellow at Pg 2.9-4.0 in the acid region. There have been prepared in recent years many new bodies belonging to the phthalein and sulphon-phthalein groups and certain derivatives having definite and restricted Py values when used as indicators. Such bodies may now be employed to determine by their colour changes the exact hydrogen concentration—or broadly speaking, the acidity, alkalinity, or neutrality—of particular solutions. Certain textile questions are thus determinable by these specialised methods :— . Acidity or Alkalinity of water supplies. 2. Residual acid or alkali in textile fibres, e.g., Sulphuric acid in wool ; Scouring residua in wool. 3. Use of caustic as against carbonated alkali or ammonia. 4. Ammonia or Silicate of Soda additions to a Peroxide bleaching bath, etc., etc. In these questions it is important to avoid mental confusion between the terms concentration, strength, etc. A strong acid or alkali is one which is highly dissociated, e.g., Hydrochloric acid, HCl, which is almost wholly dissociated even in fairly concentrated aqueous solutions. ‘“‘ or slightly dis- sociated acids such as Acetic acid, even dissolved in quantity, l1.e., in concentrated solution, exhibit only little acidity ; this depends on the amount of ionised hydrogen, which is given by the dissociation constant. These peculiarities are made full use of in the dyeing of the textile fibres. The change of colour of an indicator is always a function of (H). The hydrogen ion concentration of a solution may be measured by purely physical methods based upon electrical properties, but it is plain from the present discussion that the special ranges of different indicators may be used for this purpose ; the characteristic colours are exhibited only over definite locations. Thus Methyl Orange is red in solutions of not less than Py 2.9, and passes through orange to yellow for values of Pg beyond 4.0. Phenol Phthalein indicates from 8-10; below 8 it is colourless at all values, and for all above 10 itis pink. It thus appears possible and is quite practicable, under certain circumstances, to mix indicators so as to show different colour changes over a large range ; in other words, to prepare more or less ** Universal”’ indicators. It is equally possible to prepare solutions of definite hydrogen—ion con- centration to serve as standards of reference, the so-called “* Buffer’ solutions. Convenient compounds for this purpose. exist among the acetates, borates, phosphates, etc. Thus,

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disodium hydrogen phosphate, Na,HPO,, with a Py of 4.5, and potassium di-hydrogen phosphate KH,PO, with a Py of 9.2 could be used in mixed solutions to give intermediate reference solutions of known and constant Py, value. If, therefore, in any particular case the titration of a strong acid against a strong base is necessary, almost any indicator will serve, as the slightest excess of either from neutrality— yielding relatively large dissociation—will give a marked colour change. If, however, a weak acid or base is titrated against a strong base or acid, a special choice of indicator must be made. Thus in bleaching by solution of hydrogen peroxide, the commercial liquid has been acidified usually by sulphuric acid to secure its stability ; it is necessary to neutralise it or produce a slight alkalinity for the bleaching operation, and this is generally carried out by the cautious addition of ammonia, silicate of soda, etc. Obviously, the actual state of a peroxide bath neutralised to (1) Methyl Orange 2.9-4.0, (2) Litmus 5.0-8.0, and (3) Phenol Phthalein 8.3—10.0, would be different in all three cases. In case (1) as compared with pure water, the bath would be acid, and in case (3) it would be alkaline ; in the second case it would approximate more to absolute neutrality. Phenol Red, range P,, 6.8-8.4, is a more desirable indicator under these circumstances than Litmus, being of greater sensitiveness, having a narrower range, and also a more pronounced colour change. A case of biological interest is the serum of blood which is alkaline to litmus but not to phenol phthalein. A classification of indicators may be made on the following lines, based on the P,, values :— 0.3-6.0.—Insensitive to acids, sensitive to alkalies, e.g., Methyl Orange. 6.0-8.0.—Half sensitive to acids and alkalies, e.g., Phenace- tolin, Litmus. 8.0—-14.3.—Sensitive to acids, insensitive to alkalies, e.g., Rosolic Acid.

REACTIONS (ACIDITY OR ALKALINITY)—TEXTILE MATERIALS.

Ranken and Schnabel have shown that cotton retains Sulphuric Acid with such tenacity as to introduce large errors when the titration of aqueous extracts is attempted. Coward and Wigley prepared neutral (bleached) cotton cloth by washing with boiling neutral distilled water two samples, one of which had been previously soaked in dilute caustic soda, the other in dilute hydrochloric acid ; the cloths were then spotted by indicators, methyl red being found most sensitive. On treating the two samples with equivalent amounts of 0.005% acid and alkali alternately an approximation to neutrality within this

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limit either way could be obtained. All indicators except Methyl Red failed to react under these conditions. These authors found that errors amounting to as much as 0.05% H,SO, could occur by titrating aqueous extracts of cotton even according to currently established procedure. By spotting on the fabric itself, smaller amounts may be detected. Similar methods may be applied in investigating residual alkali and soap in pieces, and in the examination of certain types of staining.

The Carbonising Process.

The action of acids upon wool and in particular that of Sulphuric and Hydrochloric acids, finds an immense practical application in the removal of vegetable matter from raw wool. In what follows the scientific side of the carbonising process will be dealt with, as there is a distinct lack of chemical and physical treatment in the textile literature. There are some grounds for asserting that the burry and seedy wools have been allowed to go to the great carbonising works on the Continent to the detriment and hindered development of the industry in this country. The standard method for removing the vegetable matter is saturation with a solution of Sulphuric acid and concentrating this by drying on the fibre ; the cellulose becomes charred and may then be crushed out mechanically.

CONCENTRATION OF THE ACID BATH.

The sulphuric acid is diluted to a density of 1.02—1.04 or 4—8°Tw.; if the wool, as is usual, is clean scoured and carrying moisture, the bath must be slightly stronger.

SOLUTIONS OF SULPHURIC ACID.

SPECIFIC H,SO, TW. BEAUME GRAVITY. PER CENT. DEGS. DEGS. 1.02 3.0 4.4 3 1.04 6.0 7.9 6. 1.06 8.8 12.0 8 1.810 88.3 164.0 65 1.840 96.0 168 .0 66

The sorption of the weak solution of acid by the wool is very notably the same as the taking up of plain water. About 30-35 per cent. is sorbed and the fibre swelling is also approxi- mately the same in the two cases. Therefore, when the fibre, after soaking in the acid bath is squeezed and centrifuged, there remains roughly one-third of its weight of solution absorbed in its substance, say 35%, and there will be 5% of sulphuric acid reckoned on the fibre weight. By the system

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of saturation it follows that this 5% is evenly distributed on and in the wool, and also upon and in the tissue of the vegetable matter.

Fic. 16.—TANDEM WOOL ACIDIZING MACHINE. (PETRIE & McNAUGHT, ROCHDALE.)

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In the best practice, the heating stage is divided into two operations :—

(a) A drying at about 80°C. (6) A charring at nearly 100°C.

In the early stages of this part of the carbonisation there is mainly the ordinary evaporation of the water by supplying the necessary latent heat. It is a well-known fact that sulphuric acid develops considerable heat on diluting with water; the reverse operation of concentrating the acid will require this amount of heat to effect the separation of water and acid. Thirdly, when the acid strength reaches about 80% of H,SO,, some volatilisation of the acid itself takes place and a partial dissociation of H,SO, into molecules of H,O and SO,. The changes occurring in the later stages of the drying-out or ‘‘charring ’? process, are exemplified in the following table, where 146.1 grams are supposed to be concentrated to 100% acid.

WEIGHT OF ACID. STRENGTH IN H;SO,. TO BE REMOVED. GMS. % GMS. 146.1 65 — 135.6 70 10.5 125.6 75 19.5 118.7 80 27.8 ROL 85 34.4 105.5 90 40.5 100.0 95 46.1 95.0 100 51.1

At 100°C. the vapour pressures are approximately :— Acid Strength 60% 10% 80% 90% 100% Vap. Press. 140mm.60mm. lmm. 3mm. — Sulphuric acid resembles glycerine in that it will evaporate into or condense water vapour from the surrounding atmosphere until the concentration of the solution is such that it is in equilibrium with the aqueous vapour pressure prevailing. Wilson has given a table, which has been employed in much research work, of the strength of sulphuric acid required to give definite humidities in the medium above :—

RELATIVE HUMIDITY. PERCENTAGE OF SULPHURIC ACID REQUIRED AT of, 0°C. 25°C. 60°C. 75°C. 10 63.1 64.8 66.6 68.3 25 54.3 55.9 57.5 59.0 35 49.4 50.9 52.5 54.0 50 42.1 43.4 44.8 46.2 65 34.8 36.0 37.1 455 75 29.4 30.4 31.4 32.4 90 17.8 18.5 19.2 20.0

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=)

Fig. 17.—CHAMBER DRYING PLANT.

(PETRIE & McNAuGuHtT, ROCHDALE.)

In this the acidized wool from the bowls of Fig. 16 is dried, the acid solution becoming concentrated and carbonising the vegetable matter.

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The tendency to charring of the vegetable matter which leads ultimately to its complete friability, occurs in quite weak acid solutions, especially at the higher temperatures. Messrs. Coward, Wood and Barrett (Jour. Text. Inst., 1922) found with normal hydrochloric and sulphuric acids complete tender- ing on cotton in 15 minutes, and even with tenth-normal hydrochloric the same result ; N/100 acid produced appreciable tendering in one hour. Unfortunately, liquid hydrochloric acid at the higher temperatures hydrolyses wool rapidly. Dried gaseous hydrochloric on dried cotton at ordinary tem- peratures shows less than 20% of tendering in two hours at 15°C. ; with a little moisture the action is immediate. A measurable tendering is produced by evaporation at 120°C. on the fabric of its own weight of 0.01% solution of hydrochloric acid ; a 0.05% acid gives very considerable tendering at 100°C. Springer states that a boiling 4.39% H.,SO, disintegrates the cellulose vegetable material without affecting the milling properties of the wool, and that charring takes place when sulphuric acid is used in carbonising at 70—80°C. (158-176°F.). In further work, the above authors assert that the tendering of cotton by acids is roughly parallel to the Hydrogen ion concentration or electric conductivity, i.e., the “‘ strength ”’ of the acids at constant temperature, and that it is a function of the temperature. Solutions of hydrochloric acid in alcohol and ether and benzene have a greater tendering action than aqueous solutions of equivalent concentration.

PERCENTAGE OF TENDERING.

At 100°C. :— ACID 2N. ACID N. AcID n/10. Time in mins. ee: de Ee 00 HCl 100: 100° 100 . 100 100: 100 9. 54-100 H,SO, ae S00 100 > 34 100 400 12 a2 Acetic Acid 15 15 4 9 18 — 5 14 At 60°C. :— HCl 16 45 100 To 2h Re ee 9 SO. O96 Re tld 5 Ac H. — 2 Oo — QO —

The wool fibre is acted upon or hydrolysed by hot or boiling solutions of the stronger acids in concentrations beyond the carbonising strengths usual in practice. The crushing and willeying out of the carbonised burrs should follow the drying as quickly as possible to prevent the absorption of moisture, and the neutralisation of the acid should also follow quickly. Harrison gives the following as the result of laboratory tests :— “Taking 100 Ibs. of wool, airdried, with 20% of vegetable matter, carbonised with 64 Tw, H,SO, there is required about 10 gallons of or 5 lbs. pure acid. Of this the quantity absorbed by the one-fifth vegetable matter, 7.e., 1 lb. of acid will be lost by the crushing and willeying. If washed in 400 gallons of water, 2.4 lbs. of acid will be removed, leaving: 1.6 lbs. to be neutralised by soda, of which about 2 lbs. will be necessary.”

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4

as BES

ad

Fic. 18.—BURR CRUSHING AND WILLOWING MACHINE. (PETRIE & McNAuGHT, ROCHDALE.)

Here the friable carbonised vegetable matter is crushed and shaken out of the fibre.

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The soda neutralising baths in carbonising are usually worked at an excess of soda salts left in the goods is apt to appear as a white coating on carbonised piece goods. Carbonised goods seem peculiarly lable to develop defects in the after-dyeing and finishing. Lead stains are of frequent occurrence from the abundant use made of this metal in the bowls, channels, etc., of the carbonising machinery.

CARBONISING WITH MAGNESIUM CHLORIDE. This salt, as in the analogous case of aluminium chloride, is subject to dissociation at high temperatures into the hydroxide and gaseous hydrochloric acid, which effects the carbonisation, while for aluminium chloride 250-260°F. is needed, magnesium chloride required 270-300°F. As a matter of fact, the magnesium salt leaves a basic chloride or oxy- chloride of alkaline reaction, and a souring off with sulphuric acid may be required. The use of these two methods offers advantages in preserving the colours of the material, but the high temperatures necessary are detrimental to the wool. Hydrochloric acid gas is an excellent carboniser, but the plant must be specially devised.

GENERAL DISCUSSION OF CARBONISING PROCESSES. It appears, on the whole, that the sulphuric acid method is most convenient and safest, being applicable to both raw wool and piece goods, and of low working costs. One of its best features is the low temperature of carbonisation, 180-212°F. Wool may be successfully carbonised in the grease, the idea being that this will resist the action of the acid. If this method is adopted, the wool should have been steeped to remove the soluble matter, potash salts and suint, otherwise the alkaline potash compounds neutralise the acid. One objection is that some carbonised dust contaminates the greasy wool. The wool is afterwards scoured, an operation which is not facilitated by the previous carbonising. The carbonising process is easily mishandled and the spinning properties of the wool reduced. Hence, some wools, containing comparatively little vegetable matter, are carbonised in the woven piece. Experience shows, however, that such pieces are peculiarly prone to develop finishing faults, or unlevel dyeings, often quite unnoticeable in the pieces immediately after carbonising. Minute traces of lead are common in carbonised pieces, originating in the liberal use of that metal in the carbonising plant. It is sufficient to drag a wool piece over a lead surface to enable it to acquire lead enough to cause unlevel dyeing or stain by the after-production of lead sulphide in the fibre; a compound very difficult to expel from the material. If carbonising is carried out after dyeing, the choice of dyestuffs must be carefully made, or changes allowed for in the final shade.

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Some claims have been made that the cotton or vegetable elements are more absorptive at ordinary temperatures for sulphuric acid than wool, and that therefore, after centrifuging, the latter retains but little of the acid. At the higher tempera- tures the wool is very absorptive for acid. Some investigations bring into consideration the hydrates of sulphuric acid, of which the di- and mono-compounds may be of importance, e.g., H,SO,, 2H,O with 27% of water and H,SO,, H,O with 154% of water. But the previous pages have shown that the wool is by no means inactive in respect of sulphuric acid. (See papers by Fort and others on the Acid Dyebath, etc., Jour. Soc. Dyers & Colourists.)

aa eal eo

= eg é a Ted pd ae

ceil a =) a

Fic. 19.—PIECE CARBONIZING MACHINES.

(Wm. WHITELEY & Sons Lrp., Lockwoop, HUDDERSFIELD.

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The hydrochloric acid gas system appears to be gaining favour in the carbonisation of rags, various methods of using heat or mechanical motion of the material being devised. A preliminary drying is given, as quick rotting follows the action of the wet acid. The carbonising of rags is carried out in a revolving cylinder, 5 feet diameter, 14 feet long, housed in a brick chamber heated to 200°F. by the hot gases from the furnace which vapourises the Hydrochloric Acid gas. The material has two hours -exposure to the acid fumes, then stands an hour longer and is removed and shaken in a perforated cylinder. Carbonising may come before scouring; or after raising, milling, or dyeing. The arguments for and against these cases are as follows :—Goods carbonised before dyeing do not dye so well, i.e., so evenly. Goods carbonised unfelted are easier to treat than when milled ; the presence of burrs, etc., tends to fasten them into the stuff in the fulling. Goods carbonised before milling take longer to mill. Goods may be carbonised after raising in the grease.

PIECE CARBONISING.

Just as it is often convenient to dye material in piece form rather than in the fibre, so also is it sometimes economical to carbonise in the piece. Great savings may be effected by the purchase of wools and wastes containing vegetable matter, and hence unsuited to better applications, and such materials are therefore frequently employed along with a stage of piece carbonising. The system is used particularly on all-wool flannels, blankets, etc. The necessary processes are the same in principle as in the practice of carbonising fibre wool. The immersion of the cloths in piece form may be conveniently carried out in a vat of the ordinary winch type. In some cases the piece passes over the winch in an endless rope—having been sewn at the ends—tfor 4 to 6 turns, and is then unstitched and dropped into the bottom of the vat for, say, half an hour. Otherwise, it is run through the acid in the bath and batched on a roller over the trough, remaining until the necessary penetration is thought to be achieved. The next stage is the removal of excess acid, which is accomplished by the workman, by means of rubber gloves, putting the cloth into the hydro-extractor ; or, alternatively, a double mangle may be used. In either case, the drainage of acid is caught and conducted back to the soaking vat. If possible, get the pieces to the heater in not more than half an hour. The acidised pieces are now ready for the heating, which is best in the two stages of drying at a moderate temperature and final shorter spell of charring at or near boiling point of

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HEAVY RUBBER SQUEEZE ROLLERS Snes

18" DIAM CA RAT RO

PIECE CARBONISING MACHINE

Fic. 20.

STEAM HEATED TINNED COPPER DRYING ROLLERS (30 -36 ROLLERS) (ABOUT \ 14" DIAMETER). ey

J" QOOOOOO

FIRST THREE OR FOUR DRYING ROLLERS ARE COVERED WITH A FEW THICKNESSES OF WRAPPER TO PREVENT CORROSION.

78

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water, 100°C. An interval of 30 to 40 minutes of drying at about 80°C. with say, 10 minutes at 95°C., may be approxi- mately correct, but variations due to nature of wools, content and kind of vegetable matter, etc., must be allowed for. It is possible to use the ordinary tentering machine, worked at a high temperature or for longer times, to effect the carbonisa- tion, but the practice is not so perfect as the method above. Another system, of greater output, is to use cylinder dryers, as shown in the Fig. 20. The carbonised cloth must now have the charred material removed. This is commonly done in a roller milling machine of the usual flanged type, fitted to a duct and fan for exhausting the black carbonaceous dust. The operation has even been performed on the teazle gig. It could conceivably be carried out on the beater machine used for plush raising. The goods are now ready for washing off and neutralising or, if for acid milling or acid dyeing, may go direct. I The working details of the carbonising of piece goods are of importance, as it is easy to spoil the cloths, a rather expensive result on material already embodying considerable production costs. Most of the restrictions and precautions applying to fibre must be observed also in carbonising pieces ; the acid should be as dilute as will do the work, the temperature as low, the soda as weak, etc. The considerations governing the carbonising of greasy wool, as against scoured wool, apply here also in piece carbonising. Penetration is better in the clean scoured piece, and less acid is required; thcre is less fixation of dirt and easier cleansing of the piece subsequently ; it is, on the whole, probably the best system. The penetration of the acid, the after washing; neutralisation, and final washing down must all be done thoroughly, otherwise there will be streaky and patchy finished pieces. It is said that the best carbonisers are those who use the largest quantities of plain water. Acidised goods must not lie about for long periods at any stage, particularly between the heating and crushing operations. The cloths, if allowed to lie about, absorb moisture from the atmosphere, rendering it difficult to remove the particles of carbon. Evenness of distribution of acid is favoured by the use of the hydro-extractor, as against the mangle; but a double mangle may be used. There is some ground for thinking that strong light has an action on the soured pieces, leading to barry cuttles and shady lists. The carboniser should not acidise more pieces than his heating plant can handle promptly. Any want of uniformity in the amount of acid in different parts of the piece is sure to lead to unlevel cloths ; thus grease or soap residues, being “‘cracked’’ by the acid locally, will lead to irregular distribution of acid ; hard water or mineral soaps act similarly. A curious feature

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of some acidising vats is the formation of crystalline coatings on the winch or lead linings above the acid level; these, on analysis, have proved to be lime and magnesia sulphates, insoluble in the strong Sulphuric Acid, and therefore deposited out. If any of this mineral matter drops on the cloth and is worked into the fabric, local stains will occur. A very curious case of carbonising stains occurred in the author’s experience, where the cloth, delivered for white finishing (i.e., bleaching, etc.) developed light brown patches at the dry finishing end, that is after tentering; the grey pieces apparently showed nothing. There were the usual disputes and disclaimers on the part of the carboniser and the finisher alike. As lead stains are exceedingly common in carbonised working, tests were made on the brown patches for lead. Soluble salts of lead are not very common, and an attack was made on the stain by warm Hydrochloric Acid ; some clearing, not over- complete, was noticed, and the acid, collected after running through, was passed through again. It was noticed that the acid solution became cloudy on cooling, and thus a clue was obtained. As every chemical student knows, Lead Chloride is fairly soluble in hot water and comes out on cooling. The stains were therefore Lead, and their origin was apparent. The original lead had come from the carbonising plant; it existed in the pieces as Lead Sulphate, a white compound, and therefore not revealing itself. The process of sulphur bleaching —in this there are always traces of both Sulphuric Acid and Sulphuretted Hydrogen—caused the formation of some little Lead Sulphide and the brown stains. It was proved by some tests carried out by the Leeds University, during the War, that solvent scouring followed by carbonising yielded much stronger cloths, but that there was some loss of shade. Methods of carbonising by Aluminium Chloride—and even by the use of Hydrochloric Acid gas—have been attempted. While this latter is widely used on rags, it does not appear to have come into actual application on piece goods. There are grave dangers if wet Hydrochloric Acid comes into contact with wool at high temperatures. A routine of finishing on an all-wool velour, piece carbonised, is described in the chapter on Finishing Routines.

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THE CHEMISTRY OF OILS AND FAmTs.

Page 107

CHAPTER III. The Chemistry of Oils and Fats.

The practical importance of this subject to the finisher of wool textiles arises in two ways :— 1. The use of oils as lubricants in pulling, teasing, and the various stages of the spinning of yarns, necessitating their ultimate removal in the scouring operation. 2. The chemistry of oils and fats as concerned in the production of soaps.

It will be useful to classify the very diverse products com- prised under the terms “oils”? and “‘fats,’’ and a table is appended on page 84, based on the essential chemical and physical differences. The true oils and fats are glycerides—or mixtures of glycerides—of fatty acids, i.e., they are esters, glycerine being a trihydic alcohol C,H,(OH),; the waxes are fatty acid compounds of higher alcohols. Thus :— Ethyl Alcohol Glycerine C,H (O8..). Cholesterol C,H. On. The oils, fats and waxes are carbon compounds with oxygen and hydrogen, differing from the carbohydrates (sugars, starches, etc.) in that the latter have their oxygen and hydrogen in the molecular proportions of water. They contain in the non-glyceric portion the acid, COOH, or Carboxyl group. Modern research upon the constitution of these bodies shows that they consist of chains of organic radicals; a typical example is OLEIC ACID :— CH, — 7 (CH,) — CH = CH — 7 (CH,) — COOH and STEARIC ACID. . CH, — 7 (CH,) — CH, — CH, — 7 (CH,) — COOH. The commonest glycerides are Tri-palmitin, Tri-olein, and Tri-stearin ; most ordinary fats and oils consist of these in varying proportions. The widespread occurrence of acids of this type in the natural oils and fats has given the name of

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OILS, FATS and WAXES. GLYCHRIDES NON-GLYCERIDES I I I I I SOLIDS LIQUIDS ~ SOLIDS I ee es a ee pe Marine Vegetable Vegetable Vegetable I Saponif. Unsaponif. Saponif. Unsaponif. oils drying semi-drying non-drying oils oils oils

And Oleic Acid represe COOH ; and so on

Acetic acid Propionic acid CH,.CH,.COOH Butyric acid

stearic acid series are :— Formic acid

fatty acids to the series.

I I Animal __—i*Veg.

H.COOH CH,.CH

CH,.COOH

I I Liquid Waxes Mineral Fish Liver Blubber (Sperm oil) oils oil oil oil

Rape oil Olive oil Castor oil

group group group I I Alcoholic Non-alcoholic

Natural waxes Bitumen

Paraffin Wax Ozokerit Vaseline

,-CH,.COOH

nts another series of the type C,H,,_;

Thus the lowest members of the

84

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85

Fie. 21.—MAGMA PRESS. (LoNGWooD ENGINEERING Co. LtTp., HUDDERSFIELD.

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86

FAT-SPLITTING OR HYDROLYSIS.

is the separation of the fatty acid and glycerine, and may be carried out in various ways :— 1. By the use of steam at high pressure, together with I small quantities of certain bases. 2. By strong mineral acids, e.g., Sulphuric acid; and. steaming. 3. By boiling with special saponifying agents, e.g., Twitchell process. 4. By the use of enzymes. It is to Chevreul that the demonstration of the acid character of these derivatives of the oils and fats is due; it may easily be proved by dissolving in alcohol and testing with Phenol Phthalein previously made alkaline; or by gently warming with Sodium Carbonate, when Carbon Dioxide will be evolved. The natural oils and fats (except the castor oil group) are soluble in every proportion in Ether, Carbon Disulphide, Carbon Tetrachloride, Benzene, Petrol, and Chloroform ; and partially soluble in Acetic acid, Acetone, Phenol and Alcohol (ethyl). ;

UNSAPONIFIABLE MATTER IN OILS.

The great majority of natural oils and fats normally contain under 2%. A high percentage—more than 2 or 39%—renders an oil unsuitable for soap making, the soap not setting on cooling. The matter is of great importance in oils for spinning purposes, it being customary to sell such oils on a specification of saponifiable content. The unsaponifiable portion contains :

1. Suint products, e.g., cholesterol, etc., from the recovered seak-greases. 2. Paraffin hydrocarbons, olefines, resembling shale-oil products, perhaps arising from distillation. 3. Mineral oils, often deliberately introduced.

A recent analysis by Dubosc (Mat. grass, 1920, p. 535) gives, for wool-fat :—

1. Fatty acids, 54%, from the waste soap, together with some peculiar to the suint. 2. Unsaponifiable matter, 24%, cholesterol and_ iso- cholesterol. 3. Neutral fats, 21%, cholesterol ether and ceryl cerotate. 4. Colouring matter.

The saponification value of wool grease ranges from 90-102 ; it cannot be saponified by caustic alkali in aqueous solution, but requires alcoholic potash under pressure. Since the great increase of American cotton-oil soaps, the value of seak greases to the distiller has been diminished.

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Fic. 22.—PRESS PUMP.

(LoNnGwooD ENGINEERING Co. LTpD., HUDDERSFIELD.)

Fie. 23.—ROTARY PUMP.

(LonGwoop ENGINEERING Co. LTpD., HUDDERSFIELD.)

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88 WOOL LUBRICANTS AND WOOL LUBRICATION.

This question of lubricants for the process of yarn production has not received detailed theoretical study ; it is of the greatest importance, not only in itself, but in the subsequent stages of cloth finishing. Spinning oils vary from the high-priced olive oils of the fine white worsted yarns to the “ black oils recovered seak oils—of the mungo trade. The quantity used varies from 24—5% in the worsted trade to the 10-15% on the low woollen side. The requirements of a spinning oil are primarily those of a lubricant :—oiliness or slipperiness, low viscosity to prevent choking of the card clothing or combs, non-rusting properties, high flash-point against fire risks, and absence of any staining effects, particularly in the worsted and better quality yarn trades.

These requirements have, in former years, been met by the use of olive oils, i.e., of grades below the golden-yellow salad oils ; they were usually green from the presence of chlorophyll due to the methods of extraction, by boiling out with water or by solvents. The textile value is largely regarded from the standpoint of the amount of free fatty acid present. Before the modern expansion of the industry, and particularly prior to the European War, the needs of the trade were met as far as possible by this ‘“‘ Gallipoli”’ oil. Better-class Oleines supplemented this supply. The changes mentioned led, in the War, to the almost complete supersession of Olive by Arachis or Pea-nut oil, etc. ; it is stated that much oil sold as olive for textile purposes was really Tea-seed oil. It seems sufficient that a high-class textile oil for spinning should be a clean- working, non-staining, neutral lubricant, easily emulsified away in the scouring process ; and the traditional virtues ascribed to olive oil could be obtained from other and more economical sources.

In other branches of the wool trade, all grades of wool- lubricating oils are met with :—80, 75, 70, 60 and even 50% saponifiable matter; the entire range of sources, natural and artificial, animal, vegetable and mineral, being traversed for this purpose. On the organic side, oleins from the expression of fats in the candle and margarine factories ; from the animal fats of the slaughter houses, tinned-meat, lard and tallow trades ; palm oil, corn oil, cotton-seed oil, etc. ; fish and whale oils; and the low melting-point products from the recovery of greases from seak liquors, in wool and piece scouring. On the mineral side, suitable fractions of paraffins or petroleums. The blending of these is mainly left to the oil distiller or merchant, and is mainly a matter of flash-point, saponification value and cheapness, no regard being paid to the exact nature of the accumulated impurities of the product. In the lowest

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qualities, the black oils of the rag pulling industry, commonly of one-half or less saponifiable matter, form the usual lubricants; it is generally understood that these are compounded of filtered or distilled seak-greases and mineral oils exclusively. Oleic acid distils in a vacuum or a current of superheated steam at 250°C.

All oils are subject, more or less, to changes usually sum- marised as the development of “rancidity’’; from the chemical point of view this is mainly the production of free fatty acids from the otherwise neutral glycerides; though there may be actual bacterial decay of traces of animal or vegetable matter of a non-fat type present in the oil. Messrs. Tortelli and Pergami (in the Chem. rev. Fett. Harz. Ind., 1902, p. 182), give the following results on storing Oleic acid :—

INSOLUBLE FATTY ACID.

NEUTRAL- SAPONIFI- ISATION CATION

VALUE. VALUE. OLEIC A., fresh olive oil 199.5 201.4 + 2 yrs. old beef fat 191.0 202.8

5 yrs. old commercial 181.6 189.3

The differences are ascribed to the anhydrides or lactones not attacked by dilute alkali in the cold. The tradition of chemical inactivity and general inertness of oils in textile circles needs reconsideration; there are secondary effects arising from improper spinning oils which at the finishing end may render goods almost unsaleable.

SPINNING OILS AND THE WOOL FIBRE.

It is just as essential to remove the lubricants from the finished cloth as it is to utilise them in the preparatory and yarn-spinning processes. For this there must be present, at any rate in scouring by soap and alkali, a minimum quantity of free fatty acid in the lubricant. This has been variously stated at different amounts, as little as 30% being quoted. The figure is perhaps variable in respect of the other constituents, and experiments by the Drop Pipette method might establish a practical standard. In the meantime, the better the wool quality the better the lubricant it deserves. Admixtures of 80% of Oleic acid with 20% of mineral oil, both of good quality, have been used on fancy woollen piece goods with satisfaction. There is much to be said for the blending of wool lubricants from standard quality products by spinners themselves, or better by spinners in collaboration with finishers.

Oleic Acid is much thinner, i.e., is less viscous than the neutral fixed oils, e.g., olive, arachis oil, etc., and is less liable

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to leave a greasy stain. When applied to the skin, it wets it almost like water and is very rapidly absorbed. This wetting- out property of the free fatty acids probably has much to do with the quality of ‘“ oiliness ’’ (Cf. Messrs. Southcombe and Well’s paper, Chap. V), and it certainly has most potent results in the scouring operation.

Another aspect of wool lubrication is raised in the following illustration :—

Suppose a single wool fibre, 1 inch long, and take a mean diameter between the limits of 1/400 and 1/2000 of, say, 0.001 inch. The curved surface area of this fibre, considered as a cylinder is 0.00314 sq. ins., and its volume is 0.000,000,785 cu. ins. If the specific gravity of air-dried wool substance is taken as 1.33, the weight of this individual fibre is 0.000,000,038 lbs. Therefore the number of such fibres in 1 lb. of wool is over twenty-five millions, and their total surface is approxi- mately 580 sq. ft. If an oiling for spinning purposes of say 10% on the weight of the wool is assumed, this means on each fibre an oil film of roundly 1/25,000 of an inch in thickness. Now in a teased heap, the wool may occupy about one-fiftieth part of the actual heap, the other 98% being air space. Under these circumstances the problems of penetration, oxidation leading to rancidity, and drying in of the lubricating medium are fundamental to the scouring process.

Messrs. Hyland and Lloyd (J. S. C. L, 1911) state that owing to the production of partially hydrogenated oils having chemical and physical values practically identical with those of olive oil, such are being placed on the market as substitutes for olive oil for use in the worsted trade. Some of these hydrogenated oils have an iodine value almost equal to that of olive oil, but, unlike olive, gradually become tacky when exposed in thin films to moist air, as on oiled tops.

The classification of oils from the standpoint of the paint and varnish manufacturer is :—

1. DRYING; e.g., linseed oil, which forms a film in 24-48 hours. I 2. SEMI-DRYING; e.g., cotton-seed oil. 3. NON-DRYING; e.g., olive oil, which under ordinary circumstances remains liquid for months.

Livache (Compt. Rend., 1895, pp. 120 and 842) asserts that the property of absorbing oxygen and becoming converted into a tough or hard varnish, is shared by all fats and oils of vegetable or animal origin ; this transformation may be very slow, but it ultimately takes place. In any case, the infinite subdivision and enormous surface involved in the lubrication of materials like wool, necessitates care in applying the ordinary bulk

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properties of substances to such cases. It has been seen how, in the case of colloidal solutions, properties then become preponderant which are negligible in the mass. Now as mungo, shoddy and pulled wool, and as yarn, material may commonly lie in the oiled state for months and even years. The assump- tion that the lubricant then exists chemically and physically unchanged is unwarrantable, and certainly not in accordance with actual facts. In a paper on Wool Lubrication, Messrs. Richardson and Jaffe, referring to the subject of olive oils and free oleic acid, stated that the oxidation of vegetable oils produces :—

1. Increase in viscosity, and finally a solid varnish-like substance. 2. Increase in refractive index. 3. Increase in the melting-point of the fatty acids. 4. Decrease in the iodine number ; this last corresponds to a decrease of unsaturated, and an increase of saturated bodies. The mere percentage of free oleic acid in olive oil is no reliable guide to its suitability for oiling wool. If the film of oil dries to any extent, then on the surface of the fibre there is present, not a layer of liquid oil, but something more analogous to a varnish film. There must be, over long periods of standing, considerable penetration of oil into the fibre substance, and this will offer great difficulties to a scourer.

GILDING.

This is the staining of yarns by the wool lubricants—generally oleines—and is due to the presence of drying and semi-drying oils or rather the fatty acids therefrom. Practical experience has shown that such staining is intensified by exposure of the lubricated wool to wetting, as by rain, etc. Gilding stains are probably more evident in the finished goods than in the wool or yarn. Oleines which show high values by the Sulphuric acid test or its more exact modifications may be suspected of liability to cause gilding. There is a loose usage in non- technical circles of the term “‘oleines’’ as equivalent to wool oils, which is perfectly unjustified and very confusing. The extremely diverse sources now available for grease and oil recovery render all the cheaper and lower quality wool lubricants liable to carry drying or semi-drying constituents. Fish oils contain such bodies, and are quite common adulterants of poor grade wool oils. Oleic acid absorbs oxygen when impure, becoming yellow and acid, and acquiring a rancid taste and smell. The commercial Oleins (Oleic Acid) or ‘* Red Oils,” are obtained by hydraulic pressure of the hydrolysed products of tallow, palm oil, etc., and often contain much

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unchanged fat. When got by distillation, as of recovered seak greases, etc., there is some decomposition into Acetic Acid, Suberic and Sebacic acids, and certain hydrocarbons of the paraffin series resembling those of lubricating oils and petroleum. Thus a moderate adulteration of such “ oleines”’ by hydro- carbon oil cannot be detected ; normally there is 3-7%. Other unsaponifiable matters, e.g., cholesterol, may be present.

An interesting table—inserted by the kindness of Messrs. H. D. Shaw, F.C.S. and 8. Begg—upon the general question of wool oils and their effect upon the subsequent scouring opera- tions, appears on page 93.

The following table gives the particulars of the lubricants, ete.

TOTAL TOTAL GRADE. SAPONIFIABLE FATTY PRICE. OIL. ACIDS. %o %o £ Black oil 74 68 70 Australian Oleine 99 98 120 Distilled Oleine 70 65 76 Olive oil 99 5 150 Wool cream 4] 4.3 80 Soap 64 100 An analysis of the Wool Cream is as follows :— Free Fatty Acids 4.30 Neutral Saponifiable oils 33.14 Oil combined as soap 3.23 Unsaponifiable oils 1.52 Water 57.68 Insoluble Impurities 0.13 100.00

Several conclusions are immediately deducible from these results :—

1. The cheapest scours are those upon wool carrying large proportions of free fatty acids in the lubricant, thus necessitating the use of alkali only, or alkali and a minimum of soap.

2. Neutral oils—even neutral olive oils—are from the scouring point of view, almost as prejudicial as mineral oils requiring large quantities of soap for their emulsification.

3. On the whole, it seems probable that a free fatty acid content of from 60-70% is the practical datum for a wool lubricant.

Page 117

ensured, and the scouring should be cheap and efficient.

level sufficient to bring up the total for the combined oils to 60 or 70%; good lubricating property would thus be

appears to be that a spinning

A tentative conclusion of the wool lubrication problem centage—perhaps about 20 or 30—of mi

remainder should be an oleine having a high free fatty acid

oil may contain a good per-

neral oil, and the

% of oil on

Per 100 lbs. Wool

% of Free Fatty Acid.

Oil used and its Total Fatty Acids.

= Ss 13a

monorororrrser q

1D SO WD © UW) © 1) © 19 1 UW) S26

5.55 . 80 .35

> oD Ora rTrToOorwtavoosc

Pre-war best black oil 68% free fatty acid.

9° 99 99>

Distilled dleine

Neutral Olive oil 5, 29 99. 5% 9 4 Black & $ Distilled O. 663%, ss 4 Black & 4 Olive O. 4 Black & } Austral. Oe. 83% Wool Cream 4.3% Black 4 & Aus. 3

Soap to scour out

Total Cost

Cost Oil. per 100 Ibs. Wool.

Cost Soap

mG OD SHO CO PE CO OD

3 Ibs. . Ibs. Ibs. 6 lbs. 34 Ibs. 15 lhs. 16 Ibs. 6 lbs. 9 lbs. lbs. 10 lbs. lbs.

4/7 2/8 7/3 6/3 0/10 7/1 7/10 — 7/10 10/7 — 10/7 5/1 5/4 10/5 6/11 3/2 10/1 9/10 13/3 23/1 13/3 14/2 27/5 4/103 5/4 10/24 7/4 8/- 15/4 6/4 — 6/4 14/2 8/10 23/- — — 6/11 shs. shs. shs.

93

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A third result of wool lubrication is the chemical decomposi- tion—rancidity or actual decay—of the spinning oils, with the usual production of evil-smelling substances often very persistent and almost impossible to remove from the fabric. It is quite common to recognise the smell of fish-oils in the scouring machine arising from their employment in the lower grades of wool lubrication. In wet seasons, cotton-seed oils suffer great deterioration, and oleins and soaps derived there- from develop bad odours ; and corn oils also. Cotton-seed oil foots—a common, source of stock for lower grade textile soaps— has a characteristic smell of trimethylamine, a body of very persistent odour. When a scourer is accused of not having ‘“ bottomed ”’ his pieces and leaving them so that they smell, probably what has taken place is that the oil has penetrated the fibre and the scouring has not been sufficiently radical to extract this oil from these internal layers. It is not unusual for pieces to be clean and sweet at the final perch and, after warehousing or foreign transport, to develop some characteristic and undesirable smell. Such cases have arisen from bad spinning oils, from soaps made from inferior oils or ‘‘ and even from special additions to soaps, such as cresol, etc.

THE HARDENING OF OILS AND FATS.

The members of the series of fatty acids and glycerides thereof which are solid at ordinary temperatures, e.g., Stearin, are more valuable as candle-making material, and also for the harder soaps than the Oleic acids or Oleins, which are either liquids or greases under the same conditions. Reference to the chemical formule of oleic acid and stearic acid will show that these bodies differ by only two atoms of Hydrogen; a mere 1% by weight will theoretically convert the liquid olein into solid stearin. This eminently desirable change has in recent years become possible, and thousands of tons of low- grade oils and greases are annually converted into hard, white, tasteless, and inodorous fats by hydrogenation. (For details, see the technical literature, such as ‘‘ The Hydrogenation of Oils,” Ellis, 1920. Constable & Co.) It is a remarkable feature of the process that in addition to the mere hardening due to the production of the saturated Stearic acid from the unsaturated Oleic acid, an all-round purification takes place ; so that crude, evil-smelling, rancid oils—fish and whale oils, etc., formerly fit only for low-grade lubricants or for burning— are now treated so as to become good class soap material, and even edible fats for the margarine trade. Again, owing to the effects of the European War, the manufacture and consumption of margarine in this country has increased enormously ; fats and oils which formerly bulked largely as soap stock now pass into the more lucrative margarine

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market, and the quality of textile soaps has decreased, while their price has been enhanced. The Oils and Fats Restriction Order of 1918, operative during the War, left to the soap-maker whale oils and other fish oils, bone fats, linseed oil, and the lowest grades of the edible oils—the foots or purification residues ; and for linseed oils there was the competition of the paint trade. The position was further complicated by the absolute disappearance of potash soaps from the markets, owing to the monopoly of raw potash salts possessed by the Germans. This is not in itself so serious, as the pseudo-worship of the potash soft soaps in the textile industry was largely unfounded on scientific principles. But the result of all these changes was a complete inversion in the textile soap manufacture, a general lowering of quality and detergent power. This was perhaps not of the highest importance when military fabrics—made for strict utility rather than appearance—were the demand of the moment. But now that the manufacture of civilian and export fabrics has been resumed, the standards of cleanliness, lustre, bright- ness, and freedom from smells are necessarily higher ; and the due provision of good quality oils for lubrication and for soap materials is a necessity.

AN EXPERIMENT IN WOOL LUBRICATION.

An interesting experiment, unfortunately with negative results, was tried by the author using glycerine as a wool lubricant, the principal idea being to avoid the inevitable contamination of the ordinary oiling methods, and obtain a superior brightness, etc., in the finished fabric. The suggestion of glycerine in this way has been made over twenty years by a French inventor, and has been raised again at various times ; no matter has apparently been published upon the actual trials. Glycerine is a liquid of somewhat remarkable chemical characteristics. Its properties would seem at first sight to lend themselves most suitably to employment in this way :— specific gravity, 1.33; colourless, non-drying, hygroscopic, miscible with water in all proportions, good solvent powers and an excellent softener and penetrant, antiseptic, an electrical semi-conductor, non-corrosive, non-freezing in water dilutions, non-volatile at ordinary temperatures, etc., etc. Qualities were selected and blends made, and put through the ordinary preparatory woollen operations, comparative oiled and glycerined yarns being produced. There was an entire absence of electrification troubles in the carding, etc., process, but, after three or four weeks’ run, a choking of the cards occurred which eventually proved insuperable. The real difficulty is the extreme viscosity of glycerine (See Table of

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Viscosities, Chap. V), which is not overcome by any practicable dilutions with water. At the same time the superior cleanliness of the finished cloth was palpably evident, and the dis- advantages of the orthodox method of lubricating by oils markedly apparent. The results had their lessons. Whether a wool lubricant, an electrical conductor, non-viscous, non- staining, non-drying, etc., is discoverable or even a natural possibility is a research question for the future to determine.

W. B. Hardy, M.A., has discussed the problem of lubrication in relation to colloids. Water, ether, alcohol, benzine, and strong ammonia were apparently entirely incapable of main- taining a lubricating film on glass. “* Seizing’ occurred just as readily when they were present as it did with cleaned surfaces. Glycerine differed from those fluids in the fact that, though it would not maintain a lubricating film, it did prevent ‘* seizing ’’ when present in excess. For instance, the maximal tangential force which a certain pair of cleaned surfaces would support without slipping was, measured in grammes, 55. Flooding the surface with water, benzene, alcohol, etc., left that value unchanged. When a film of glycerine was deposited on the surfaces the force stood at 55, measured in grammes, but it fell as the quantity of glycerine present was increased to 9, when the surfaces were fully flooded. The expression film ’? denoted a layer of fluid on the solid surface, so thin as to comprise probably only a single layer of molecules. With a true lubricant the facility for slipping was maximal when a layer of such excessive tenuity separated the solid faces, and nothing was gained by increasing the thickness of the layer. Thus with castor oil the weight required just to start one face of glass slipping over another was 10 grammes, when only the invisible film of fluid mentioned above was present, and it was still 10 grammes when the surfaces were flooded with oil. Some fluids indeed seemed to lubricate better in thin than in thick layers; to act, that is to say, in the contrary way to glycerine. Acids as a class behaved in that way, the solid faces again being of glass. The pull in grammes was as follows :—

FILM. SURFACE FLOODED. Acetic acid 40 47 Sulphuric acid oF 47 Oleic acid 10 13

If that result could be fully substantiated it would be an important and striking physical fact likely to throw much upon the process of lubrication.

One broad conclusion emerged, namely, that lubrication depended wholly upon the chemical constitution of a fluid, and the fact that the true lubricant was able to render slipping

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easy when a film of only about one molecule deep was present on the solid faces suggested that the true lubricant was always a fluid which was adsorbed by ‘the solid face. If that be so, then the problem of lubrication is merely a special problem of colloidal physics.

General Discussion of the Wool Oiling Problem.

The application to the wool fibre in the various operations of pulling, carding, combing, etc., of oils is one of the neglected topics of textile literature, particularly in the secondary aspects of the problem. Primarily the oiling of wool is in essence a lubricating process intended to facilitate the progress of the fibres through the different machines; it is peculiarly an empirical routine, but little scientific study having been directed to the question, and very little published information exists in the trade journals or textbooks. In certain special cases attempts are made to dispense with oiling and its attendant drawbacks. The oil of the combing process leads to difficulties when fine goods are dyed in light and delicate shades. Here lies the superiority of the so-called ‘“ of tops, which might be more accurately termed ** tops free from oil,”’ a speciality largely identified with the French spinning industry. In the first method of pro- ducing such tops, the wool is taken from the card and backwashed ; the slivers are then twice gilled, punched and combed. The French process retains the oil on the fibre through the comb ; from.the card the slivers are gilled, punched and combed, and put through one finisher before backwashing, a good deal of the oil having thus gone with the noil. The broad outlines of fibre-oiling in the woollen and worsted trades may be summarised as follows :—

I. WORSTEDS.

The wool is sometimes worked dry, otherwise oilings of 2—3°% on the weight of the wool are employed. Olive oil is the principal lubricant along with wool creams of variable composition and the better class oleines. Admixture of mineral oils in this case is supposed to be not permissible, and neutrality, i.e., absence of free fatty acid, as desirable as price will permit.

Il. WOOLLENS OF GOOD QUALITY.

These are oiled_in the initial stages in quantity up to 15%, generally with the so-called ‘‘ Oleins ’’—i.e., crude oleic acids— containing high percentages of free fatty acid along with mineral oil in amount of 20-30%.

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98 Ill. LOW WOOLLEN GOODS.

Composed of recovered and low quality wools and cotton ; heavily oiled in both the pulling and blending operations, often more than 15% on the weight. The oils are low grade oleins with much addition of mineral oils and of low percentage saponifiability. It is thus evident that extreme diversity exists in the requirements of the wool trade for fibre lubricants, and that different criteria are applied in the various sections of the industry. Thus the topmaker insists on neutrality and absolute freedom from mineral oil ; the shoddy manufacturer demands cheapness, and the maker of fine woollens accepts cheerfully a 4 to 1 mixture of free fatty acid and paraffin oil ; The spinning requirements are rarely considered in connection with the subsequent removal of the lubricant from the woven fabric in the scouring shed, and the oil merchants are in general completely ignorant of the textile processes through which their products pass. The usual standard for the dealer in wool lubricants is to specify the oils on a basis of Total Saponifiable Matter. This is, of course, a purely laboratory or chemical having little or no relation to lubricating property or otherwise to scouring practice. In this latter aspect, it has never yet been determined how much of an average alkaline ‘scour is saponification and how much is emulsification, and it is certain that the latter process is preponderant. Hence it is desirable to specify wool lubricants also in terms of Free Fatty Acid, which is occasionally done on the worsted side for olive oils, where excess is said to be prejudicial ; it is particularly necessary for woollens, where the efficiency of the scouring process is directly dependent on the nature of the wool oils.

Oiling for Worsteds.

Olive oil, which at one time during the War was quite unobtainable, is still the highest class lubricant in this section, its value varying inversely with the percentage of free fatty acid. Fresh olive oil, likely other newly prepared animal and vegetable oils, is almost neutral. It is stated that 6% is the maximum amount of free fatty acid permissible in an olive oil for worsted yarns, but it is certain that this limit is commonly exceeded. ‘* olive oils have been found to contain even 20°% of free oleic acid and prove satisfactory in working, and Seville oils, with only 2%, have exhibited greater viscosity than the Gallipoli oils with the higher percentage. It is asserted—but needs verification—that free fatty acids :— 1. Tend to cause stickiness in the combs. 2. Diminish the fineness to which a given wool can be spun. Olive oil is said to permit 8—10 counts finer spinning than olein.

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3. Tend to oxidise more than neutral oils. This is perhaps established. 4. Diminish the speed of spinning. The subject has received so little inquiry and is so unsettled, that further discussion is desirable. The alleged ** stickiness ”’ seems inexplicable, in view of Messrs. Southcombe and Well’s conclusion that the free fatty acids are the potent cause of the lubricating power of the common oils and also the remarkable effect in increasing the “ oiliness ’’ of mineral oils. Mr. F. W. Richardson, when exposing oils to currents of hot air, did not find increases of viscosity varying with content of free fatty acid :—

OLIVE OIL. Seville, 2% free fatty acid, Increase of viscosity 32.6 units. Gallipoli, 28% ‘a £0:

Nor when tested in the Mackay oil tester for spontaneous

combustion did the oleins show much suspicious tendency :— TEMPERATURE IN 14 HOURS (F.).

Cotton Seed oil 381-540 Olive ; neutral I 214 Olive ; fatty acids 406 Olein 216 Olein 97% 216 Olein, Belgian 212

The three oleins are almost entirely composed of free fatty acids ! The question of attack by oils containing large proportions of free fatty acids is another obscure matter. It is known that such oils do not store well in iron drums or vessels ; on the other hand, traces of sulphuric acid used in the purification of oils, animal, vegetable, and mineral, are present in the com- mercial products and may be more potent for mischief than the oleic acid itself. The corrosion of card wires does not appear to be excessively rapid in the woollen section, where the oils have enormous percentages of free fatty acid. It is difficult to apportion the relative responsibility of friction, free fatty acid, and traces of mineral acid, but cards working on wool oiled with 95°% oleic acid have lasted forty years. Smith, however, has stated that in the worsted trade the average life of the card clothing was about two and a half years, on night and day working. There have been from time to time isolated instances of troubles due to oiling in the textile industry, and perhaps the most general and severe case on record occurred about the years 1919-1921, after the close of the War. In the worsted trade, the damages amounted to many hundreds of pieces and losses of thousands of pounds. There is always a sufficient

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volume of defective work going on in the textile trade to account for an ordinary percentage of damaged pieces, but exceptional quantities demand special explanation. In this particular instance, the defects were not revealed until the pieces were dyed, when an abnormal degree of variation of shade was observed, i.e., the dyeings were “ shady ”’ or unlevel. The special faults in question occurred on piece-dyed worsteds in various weaves and in diverse shades. The fabrics showed streaks, bars running sometimes with the warp or sometimes weft-way, or map-like areas of irregular outline ; the markings occasionally crossed the warp and weft in perfectly haphazard fashion. The markings were sometimes lighter, sometimes darker than the general ground shade of the piece, and they were not confined to the edges of the piece in special excess. The epidemic occurred in various textile towns, and was very general in the commission dyeing and finishing firms. On indigo and blue fabrics it was very common, but this, of course, is to be expected, in view of the relative frequency of these pieces. There is in the industry a considerable mass of information upon the nature and causes of streaky, barred, “ listed ’’ pieces, and on the origins of unlevel dyeings ; all the known hypotheses of irregular spinning and weaving, of dyers and finishers’ stains, of mildews, of defective manufacture of dyestuffs, were brought to bear, and in some instances these were possibly adequate. But the wide and general distribution of the defects and their mode of occurrence, precluded any of the more ordinary and usual faults of manufacture fully explaining the matter. In certain cases it had been noted at the grey perching, prior to dyeing and finishing, that the pieces were slightly uneven ; even on the general dirty creamy yellow of the woven pieces, areas of slightly deeper shade were noticed. Extraction tests by Ether or by Soxhlet apparatus revealed in these areas and on the uneven areas of the dyed pieces, some oily matter of a very viscous nature, and there were grounds for concluding that this was present in such areas in excess of the general average of the fabric. The oily or greasy matter thus extracted showed evidence of oxidisation or polymerisa- tion ; after extraction it was, if not actually hardened, at least “tacky.” It was very resistant to the ordinary scouring reagents, e.g., soap and ammonia, and insusceptible to emulsification. Occasionally, the scouring of these goods was assisted by the employment of special solvents, e.g., Tetra- chlorethane, and quite a stimulus to the trade in these preparations was given, owing to the particular difficulties of the time. It is known that in the case of the blues the position was complicated by the bad quality of some of the dyestuftis of British origin at the time; a well-known topping blue of

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Sulphocyanin type in general favour was at one particular period responsible for much damage. Further, the great sub- division of the worsted trade prevented the direct location of the faults and defects; it was not possible to secure the co-operation of a spinner in tracing the origin of damages which had appeared—and were probably merely developed— after dyeing. It is, however, certain that the principal cause of these very widespread defects lay in the oiling of the yarns and in the comparatively long storage which the conditions of trade at that time had brought about. The orthodox olive oil of the trade had been largely replaced—owing to export restrictions by the Italian and other governments—by substitute oils. Of these, Arachis or Peanut oil was the chief, and Tea-seed oil was also used. These have sufficient general resemblance to olive oil to make substitution easy, and possibly, if quick manu- facture of the yarn into fabric follows, their employment need cause no defects. But investigation shows that they have more marked drying properties than the best olive oils. Thus, while a Gallipoli oil showed a percentage increase of viscosity on exposure of 10.5, a sample of Arachis oil gained 116. Even olive oil in long periods is subject to changes such as are exemplified in the appended table :—

BUTYRO- IODINE MELTING POINT REFRACTO- NO. OF FATTY ACIDS. METER. Pure Olive Oil 83 27 39 Oil from old Wool Tops 52 354 48 Oil oxidised 2 hrs. in air at 400°F. 50.4 364 441

(Richardson. ).

The normal constants of the three oils mentioned above are — as follows :—

SPECIFIC SAPONIFICATION IODINE GRAVITY. VALUE. VALUE. Olive oil 0.915-8 190 82 Arachis oil 0.917-9 189-193 90-100 Tea-seed oil 0.917 185 84

NOTE ON VALUE.’’

This is the percentage of iodine absorbed by a given oil, and is a measure of the unsaturation of the oil, i.e., its general tendency to absorb and combine with oxygen from the air ; and consequently to develop colour changes and drying properties with formation of sticky films. The value for the non-drying oils, e.g., olive and lard oils, etc., is about 90 or less. That of the semi-drying oils, cotton-seed, rape, etc., is 100-140, while for linseed it reaches 180-200. (See later).

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According to Holde and Winterfeld, a sample of olive oil, after standing exposed to light and air in a flask for 21 months, showed a rise in specific gravity from 0.914—0.916 at 15°C., an increase in viscosity from 563 to 598 seconds by the English viscometer, and a decrease of 4° in iodine absorption. The relatively enormous distribution of the oil in wool lubrication must always be remembered in this connection. It is known in certain quarters that if yarn is to be scoured immediately after spinning and then dyed or sold, a lower class of oil may be used than when the yarn goes into storage for some time, or even when the pieces are woven and lie up in the grey unscoured state before ordering forward for dyeing and finishing out. Cases have been quoted where yarn spun in olive oil and stored in a light warm room showed the pattern of the wickerwork of the basket reproduced on the wool when taken out. Another dangerous factor in olive and “ red ”’ oils is the presence of iron, which in very small amounts exerts a catalytic action, leading to rapid heating and oxidation.

(A. H. Gill.)

In cases of defects involving chemical considerations, and especially in fats and oils, it is well to bear in mind the limita- tions of chemical analysis. Genuine specimens of oils vary. greatly in their constants for all kinds of reasons :—Locality, age, mode of extraction, refining, etc. In addition, the re- sources and accuracy of technical chemistry in respect of fats and oils are much less than those of inorganic substances, e.g., alloys. Large percentages of Arachis oil or Tea-seed oil could be added to olive oil without fear of detection; and in a lesser degree adulterations by Rape oil, which is distinctly semi-drying in character. G. D. Eldson, F.1.C., states that :— ‘‘ At the present time, however, it is not possible to determine with reasonable accuracy and speed the amount of any one single fatty acid in any ordinary oil....... It follows that for the purpose of testing oils and fats we have to use figures such as the Iodine,

Saponification, and Reichert values, which are of course the average values.”

Hydrocarbon oils undergo oxidation changes, e.g., bearing lubricants, in which the copper of the brasses acts as a powerful catalyst. The mineral oils used in electrical transformers deposit in course of time a “sludge,’’ a change attributed usually to oxidation. Such altered oils will yield an emulsion on shaking with water, especially in presence of alkali. Napthenic acids are said to show this effect. The presence of asphaltic or bituminous bodies is becoming suspected in certain mineral oils ; such constituents should be investigated. Oils containing such acids are sometimes treated by dilute solutions of trisodium phosphate. Messrs. Scheurer and Wallach (Bulletin Ind. Soc. Milhouse, 1913), state that no mineral oils

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could be found by them which did not stain, and they recommend that the best non-staining preparation is a mixture of 75% colza (!) with 25% of mineral oil. The selection of colza looks curious ; why not a good olein ? (Author). Soda washes used in removing the traces of sulphurous acid in the refining of lubricating oils are sometimes permanently emulsified. This has led to investigation, and the sodium salts of naphthenic and sulpho-naphthenic acids have marked emulsifying properties. Soda naphthenates have been used as soaps.

WOOL CREAMS.

These fibre lubricants are practically confined to the worsted end of the trade and are of the nature of emulsions. They are widely used, being cheaper than oils, and are stated to have advantages in diminishing electrification and preventing corrosion of the plant, besides being easily removable in back- washing and scouring. The utmost variation exists in the details of the composition of these preparations, but essentially they are soap emulsions carrying oil dispersed throughout the medium. They are commonly made up in the works and should regularly be so prepared for the double purpose of economy and the avoidance of undesirable adulterations. A typical formula is appended :— I Potash soap 1 Ib. Water 20 Ibs. that is, a 5% solution of soap. Add olive oil, one gallon, and stir to a uniform cream.

A second example varies the type of soap :—

Water 2 quarts, warm. Olive oil 1 quart. Ammonia 1 gill,

thus forming an ammonia soap carrying the oil in an emulsion,

But oleins, cotton-seed oil, etc., with various soaps, borax, pearl ash, etc., are used, and even additions of mineral oil. It is obvious that there can be no justification for paying excessive trade prices for compounds of this description. In certain cases, use is made of sulphonated oils, i.e., Turkey Red oils, the low surface tension and marked wetting-out power lending these readily to good emulsions ; but damages arise from their great penetration when there is any want of uniformity in application, and subsequent dyeings may prove unlevel. Gelatinous substances such as extracts of [rish Moss are unsafe additions to wool creams. On knitting yarns a 10% soap solution (1 lb. soap per gallon water) with 14 lbs. oil added is commonly employed. For cotton yarns the threads often run through two cakes of paraffin wax on the winding frame. The emulsion on the wool yarns increases the extensibility of the

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threads very greatly, even up to 200% on the dry fibre, but there is usually a decrease at the same time in the tensile strength. Dr. Lloyd has stated that if treated mineral oils are employed, even worsted and mohair goods may be worked with a mixture of 30° such oil and 70% olive oil, preferably used in emulsion form ; ammonia is not owing to its ready action on brass and copper. Similar emulsions are employed in the hosiery trade, where yarns are damped by passing over rollers working in the lather. One gallon of soft water containing 1 lb. of curd soap with half a pint of good yarn oil is a mixture recommended for this purpose. If more damping is required, run the roller faster in the solution.

The QOiling of Good Woollens.

Presumably the usual 10° of oil on the weight of the wool in this section is a datum arrived at from experience, and must be necessitated by the presence of the short fibre in the blend. The employment of these larger amounts of lubricant compels the use of cheaper oils, and oleines of varying quality form the basis ; admixture of mineral oil is also general. A typical oil for high-class woollens might be compounded from :— OLEIN (soap oil), of 95° saponifiable quality, 80 parts. MINERAL OIL; say, 0.885 Scotch Paraffin, 20 parts. If this is too viscous in winter, substitute part of the mineral oil by kerosene, i.e., “‘ water-white ’’ paraffin oil, commonly called lamp oil.

Now this is plainly a complete departure from the practice at the worsted end, and raises a number of novel and generally unsettled questions :—

1. Nature of the Oleins, i.e., distillation or saponification oils. 2. Nature of the mineral oils, American, Scotch, or Russian. 3. Limits of the mineral fraction. I 4. Effects on the fibre. 5. Scouring operations on the resulting fabric, etc., etc.

The operations of the producer and refiner of oils consist in the main of the following processes :— 1. Saponifying the raw fats ; hydrolysis or fat-splitting. 2. Distilling the resulting fatty acids. 3. Pressing the products of the saponification or distillation for the separation of liquid ‘*‘ Oleins ’ from the solid stearic and palmitic acids, these latter going for candle making.

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The saponification oleins obtained by pressure from the fat-splitting without subsequent distillation are darker in colour and contain some amount of neutral fat, while the distillation oleins are paler, but invariably have also some unsaponifiable fractions from the decomposition occurring in the stills; their colour may be still further improved by redistillation. The red colour is due to decomposition products and to iron soaps (Oleate of Iron). Saponification oleins may be used directly as soap stock ; diluted with mineral oil in the proper proportion, they are employed as wool oils, and the distillation oleins are similarly utilisable. Expressed olein is commonly termed ** Red Oil,’’ and there is a common delusion in the textile trade that red oil is the oleic acid portion of palm oil, which has a natural orange-red colour ; in point of fact, red oil is the product of all kinds of raw fat stock subjected to splitting and refining. It always contains some amount of more solid fatty acids, e.g., stearic, but is essentially crude oleic acid. Its saponification value is usually very high, over 95%, and as more fully described later, it can be made into an excellent textile soap. As already stated, not only the saponification value, but the percentage of free fatty acids should be known on purchase.

The mineral oils added to the oleins in the compounding of wool lubricants have in the past been derived from American, Scotch, or Russian sources. Of these, the Scotch oils are distilled from shales and the American oils tend to contain more unsaturated hydrocarbons than the Russian type, i.e., more terpene and olefine-like bodies. Statements have been made in textile circles that the order of preference is Russian, Scotch, American, but no very obvious or well-founded basis is put forward for this conclusion. Varying densities are used in summer and winter. A more important question is that of the amount of added mineral oil permissible in the lubricant. I

The fundamental principle controlling this matter is that while the olein of the wool oil is readily saponifiable and easy to emulsify, the mineral oil—being of hydrocarbon, as distinct from fatty acid constitution—is perfectly unsaponifiable, and does not lend itself easily to emulsification. There is a long record of works’ experience behind the blending of olein and mineral oils for wool lubrication, and the question has received some experimental treatment by Spennrath (Dingler’s Poly- technic Journal, Vol. 294, p. 44). Wool was oiled with varying mixtures of olein and mineral oil, and subsequently scoured with a soda solution of two per cent strength (4 Tw.). The percentage of oil remaining was then determined. A

similar set of experiments was then carried out in which the olein was replaced by olive oil.”

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PERCENTAGE OF ToTAL WEIGHT OF OIL

MINERAL OIL. LEFT AFTER SCOURING. WOOL OIL OLEIN—MINERAL OIL OLIVE—MINERAL OIL 10% is 1.19 20 1.55 30 0.4 2.05 40 1.78 2.83 50 1.98 3.50 60 2.01 10.58 70 2.17 11.66 80 4.80 15.37 90 11.65 28.20

It thus appears that 30° of mineral oil in a wool lubricant is the maximum consistent with proper scouring and complete removal from the fabric. A standard wool oil used in enormous quantities in the trade is compounded on the 80 : 20 basis and is well known to work perfectly when the woven cloths go to the scouring and milling departments. In such a case, the scouring may be well-conducted by the use of alkali alone, 1.e., it may be a Saponification Scour. As will be seen later, wool lubricants containing high proportions of mineral constituents are widely used, and it is notorious that difficulties are ex- perienced in the subsequent scouring. The complications due to mineral oil have led to widely diffused prejudices against its employment in textile particularly on the worsted side, but it is certain that even if costs permitted, the use of pure oleins would, in heavy oilings, be inadmissible. In a case within the author’s knowledge, a straight “‘ soap oil ” of 95°% saponifiable quality was employed as a wool oil, but the difficulties of scouring proved insuperable. There would in such circumstances be a tendency to form Water-in-Oil emulsions in the scouring machines; that is, emulsions of reversed type to the ordinary scour, which is of the Oil-in- Water kind. Such reversed emulsions are troublesome to rectify, and. pieces scoured under such conditions are liable to contain residual oil and develop smells. It is probable that the mineral oil has an inhibiting action in preventing oxidation of the fatty acids,

Among secondary effects due to the use of mineral oils in wool lubricants, there have undoubtedly been the production of special stains. Mineral oils turn yellow under the action of light ; quite moderate exposure to strong sunlight causes a slight browning of a fabric carrying mineral oil. Accidental oil stains from machine bearings may develop this change, but it has undoubtedly occurred from the mineral component of the wool lubricant itself. The exposure and staining may occur at all stages, tops, yarns, and woven cloth being liable and the steaming in conditioning of a certain type seems to intensify the effect. Some tests showed that the Scotch shale oils were more susceptible to this light-change than the

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American type. Mineral oils treated to remove the un- saturated bodies are on the market and have passed experi- mental tests for light-staining successfully. Oleins tend to bleach under the action of light. Many so-called * Stainless Oils ’ are sold for the lubrication of textile machinery which are supposed to have the property of scouring out without leaving a stain. In general they are better quality and more or less colourless mineral oils free from acidity due to purifica- tion, sometimes bleached by animal charcoal or china clay, etc. Their stainless character is a matter of degree. The pure white deodorised petroleum used for toilet and medicinal purposes is capable in the course of time of developing the light-change alluded to above ; a specimen in the author’s possession, kept. in a bath-room window for several months in a south-east aspect, is a pronounced yellow tint. Dr. L. Lloyd states that the yellow matter of these mineral oils is an oxidation product of the naphthene series present in the oils and that even bleached oils could oxidise and produce yellow films. Mineral oil treated with dilute acid permanganate 0.02% or perman- ganate and caustic soda 0.05°% was rendered practically colourless, but if the naphthenes and other oxidisable products were not removed, it would turn brown on the fabric. The operation of chroming tended to attack and resinify the naphthene bodies. Traces of iron or copper with mineral oil intensified the staining enormously. (Jour. Soc. Dyers & Col., April, 1921). There are some grounds for believing that mineral oils possess greater powers of penetration into the wool tissue than the oleins, and that this may be the cause of the difficulty of scouring out these bodies. The great extension of the use of ’ in the scour is due to the desire to deal more thoroughly with the unsaponifiable portions of the wool lubricants ; as will be seen later, the idea is largely a fallacy on the theoretical side. The extended growth of the margarine industry during and since the War, has led to a corresponding increase in the manufacture and use of cotton-seed oil, which is a principal “ fat-stock ’’ in the trade. Much larger quantities of cotton oleins of varying quality are now on the market, and these are invading to a greater extent the textile industry, both in the soap and wool-oiling applications. In the latter aspect, it must not be forgotten that cotton-seed oil belongs to the semi-drying type. Its purification is usually effected by treatment with warm dilute caustic soda to combine with the free fatty acids and the natural colouring matter ; on standing, the lower aqueous layer or “ foots ’’—consisting of a soap solution, vegetable gummy matter, and pigment—is made up into low-grade soaps. These, imported during the War to

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meet the scarcity of soaps, are still used in low scouring on account of their cheapness. They are usually very dark in colour and evil-smelling, and are totally unfitted for better-class work. The cotton oleins are largely blended with mineral oils for wool lubrication, and percentages of thirty or even more have proved quite practicable ; in fact, a cotton olein used by itself would be objectionable. These are distinctly useful in the lower grades of wool oils.

The Oiling of Low Woollens.

These goods, composed of the cheaper fibres, cotton and recovered wools, must inevitably be treated with corresponding- ly cheap lubricants. The “ process of recovering wool fibre from rags consumes much oil in addition to that applied in the subsequent blending for the spinning operations. The total oiling of these goods may thus exceed 15% on the weight of material. Hence large additions of mineral oil are made to the lubricants for low woollens, and the olein content diminishes accordingly. Further, the grade of saponifiable oil is lowered. Extensive use is made of recovered oils, i.e., those extracted from waste greases from all sources, whale and fish oils, foots and purification residues. In the manufacture of shoddy it has been recommended to let the rags lie for twelve hours with an addition of 18° of warm oil, in order to retain the staple fully. Carbonised rags require more than un- carbonised material. The grease from scouring liquors—seak grease—is subjected to a partial refining by sulphuric acid, etc., followed by distillation ; the resulting oleins in the poorer qualities come into low woollen lubricants. It is evident that in these operations much decomposition occurs and hydrocarbons are formed ; the proportion of unsaponifiable matter increases greatly. Oleins of all grades, 70, 60, 50, 40, and even 20% of total saponifiable matter are produced, blended with mineral oil to the necessary: liquidity. If natural oils are employed, the cheaper cotton-seed or corn oils, etc., are utilised. It should be understood that in the textile trade, at any rate, the word “‘ OLEINE ” means—not any definite or chemically exact product—but merely Wool Lubricant ; no implication of origin, purity, or suitability is conveyed. A usual mixture in the trade is made of equal parts of olein and mineral oil. Under these conditions the difficulties of the scourer of low woollens are greatly increased. Some suggestions for the working of these cloths are made later in the section on practical scouring, but much might be gained by a more intelligent selection of oils in the blending of low woollen lubricants. It is often assumed that the brown oleins are superior to the

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“black oils”? for wool oiling, a conclusion by no means legitimate. The criterion, as regards the scouring, is the proportion—not of total saponifiable matter—but of free fatty acid. In this respect some of the black oils—contaminated by fibre flock or carbonaceous matter—stand high and are easily removed from the cloth in the scour. An oil might be fairly light in colour, but if it contained much grease from raw wool. scouring, would be far less removable than a black oil rich in free fatty acids. Such oils as these are to be preferred. In any case, special methods and precautions must be used in the scouring of fabrics carrying oiling of the low woollen type. Morawski has said that 80° of a mineral oil with 10% of oleic acid is emulsifiable in a soda solution of 0.5°% concentration. The residues from raw wool scouring containing lanolin-like- substances are unsuitable constituents from the scouring point of view, belonging to the unsaponifiable portion of the lubricant. A scourer is primarily concerned with total emulsi- fication ; large additions of mineral oil and some other matters destroy his emulsions and ruin his scours, but free fatty acid favours his operations, and hence a knowledge of its presence and amount in the wool lubricant is valuable.

It would seem that in the minds of oil merchants, blenders, and some others there is a sort of hazy notion that the free fatty acids of oleins, olive oil, etc., are quite analogous to the strong corrosive mineral acids, e.g., vitriol, spirits of salt, etc. It is possible to find statements in advertisements and even in technical lectures that the acid oils have a corrosive effect on the serrations of the wool fibre; that yarns spun in acid oils form greasy soaps in the goods and will not cleanse out properly ; that “ neutral ”’ oils “‘ feed the wool ”’ better ; that neutral oils produce “ loftier’’ fabrics; that the free fatty acids produce harsh dead effects on the wool, as opposed to. the feeding and fattening effect ; that oleines of the acid type, while giving a good foam and lather in the scouring, do not lift’? very quickly out of the cloths; that the average distilled cloth oil containing a high percentage of free fatty acids is bad for wool, etc., ete. I

Such assertions, ill expressed, based on no accurate experi- ments or observations, or even on intelligent practical working, show the need for real scientific study of the subject of wool lubrication. It is remarkable, considering the large interests represented by the wool textile industry, how obscure is the basis of certain of its fundamental operations. The mechanical aspects of wool lubrication are practically unstudied. There are three main stages of lubrication which are sufficiently defined from each other to lead to the conclusion that different. laws are concerned :—

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STAGE OF LUBRICATION. LAWS. ee OF FRICTION. Unlubricated Surfaces Dry Friction 0.10-0.40

Partially Lubricated Surfaces Greasy Friction 0.01—-0.10 Wholly Lubricated Surfaces Viscous Friction 0.001-0.01 In the first class the surfaces are separated by thin layers of air, in the second by a thin layer of lubricant adsorbed by the surface, and in the third the solid moves in a quantity of liquid, i.e., there is fluid friction. The calculation on p. 90 shows that in actual working, if uniform distribution of the lubricant on the fibre is assumed, the oil film must be of the order of a few millionths of an inch. But Lord Rayleigh’s experiments ‘“‘ On the Lubricating and other’ Properties of Thin Oily Films ”’ have shown that films of this thickness are sufficient to lubricate surfaces and minimise the resistance to motion. In some cases the friction was greater with large than with small quantities of oil.

Special Notes on Qils and Fats. TALLOW.

Mutton and beef tallows, in their better qualities, formed the original margarine, but vegetable fats are now largely used, and even hydrogenised oils. Other qualities of tallows go to the soap and candle trades. Hard tallows, made into soaps, do not lather freely at ordinary temperatures. Textile soap flakes, milling soaps, and white curds have usually a tallow basis blended with a bleached palm oil or free lathering material like coconut oil or palm kernel oil in the best qualities ; but probably hydrogenised oils are now used. The soaps so generally known as “ primrose,’ often used in laundries, are

tallow-rosin soaps, perhaps with 15-25%, rosin. “Pure tallow soaps are difficultly soluble, and lather very poorly, so that the same property may be looked for in a hardened fish oil or whale (Seifen. Ztg., 1912, p. 1003.)

COTTON-SEED OIL.

The best refined qualities are used for ‘edible oils, e.g., Compound Lard, the lower sorts for soap-making, the foots also coming into soap stock. Though of fairly low melting-point or ‘*‘ titre,’ 34°C., the resulting soap is soft ; it is employed in making soft soaps possessing the “ figging ’’ feature, mistakenly considered in some textile quarters to be a sign of detergent power. The crude qualities are dark coloured and often badly-smelling ; textile fabrics scoured and milled with cotton oil soaps sometimes develop offensive odours on warehousing or transportation. Maize or corn oil in soaps may produce the same effects. Cotton oil should not be used as a wool lubricant, owing to its too spontaneous combustion and its tendency to partial drying.

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A reddish-brown grease having a characteristic violet-like smell communicated to the soap. This oil, subjected to the splitting process for the removal of the glycerine, yields ‘‘ Red oil,” or “‘ Oleine,”’ a 97-100% oleic acid, which comes into the textile industry in enormous quantities as a wool lubricant and for the manufacture of olein (?) soap. The oil from the palm kernels, very similar to coconut oil, is used in good quality soaps to confer lathering property.

RESIN OR ROSIN.

This is not in itself an oil or fat, but is conveniently treated here as a soap constituent, being commonly added to low- quality soaps to give lathering power and for cheapness. It contains organic acids capable of neutralisation by alkalies, and produces an easily soluble soap, freely frothing, and with a characteristic but not objectionable smell. It is an impossible material for textile soaps on account of its decomposition by the calcareous or magnesian salts of hard waters—resinates of these bases are produced, depositing on the cloth. Resin soaps absorb water and become sticky. * * * * * + * The question of the lubrication of wool is now becoming a subject of research. A paper by Rhys Davies (Jour. Text. Inst., April, 1926) was followed by an interesting discussion. The lecturer discussed, in particular, the changes occurring in wool lubricants and especially olive oils on storage, exposure, etc. Oil had been extracted from wool tops and showed definite characters :— A darkening of the oil. Distinct differences in odour and taste (rancidity). More viscosity. Increased refractive index. Ever diminishing iodine value. Increase of the “‘ titre ” of the insoluble acids. Notable rise in the specific gravity. The oxidised oil acids become chromogenetic and stain wool a brownish yellow colour, not removable in scour- ing by any known chemical agent. 9. The oxidised portion of the mixed fatty acids has a characteristic insolubility im petroleum ether, but is readily soluble in strong alcohol; hence they can be determined quantitatively. The above criteria may be instructively compared with Richardson’s data, and information respecting the staining epidemic on worsted goods, in Chapter III, on oiling. Commercial olive oils are dealt with on a usual basis of free fatty acid, say, not more than 5%. But it has not been

wt

OF Gr SS

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clearly recognised in the textile trade that this oil may undergo rapid deterioration. In a few months, the oil may show 15% acidity or more, i.e., oxidation of the neutral glycerides has occurred. The circumstances of this change are peculiar. Some oils will degenerate and oxidise more rapidly than others on the wool fibre, although their iodine numbers are very similar and their free acidity figures are very similar. (Cf. Richardson and Jaffe.) One oil having an initial free acidity of 2.82% and no apparent traces of oxidised products, after contact with clean scoured wool—3% of cil on wool—

gave figures :— MONTH :— ONE. TWO. THREE. Acidity as free oleic acid 5.70 10.97 ie 1) Oxidised oil acids 12.75 14.21 19.63

On four oils actually extracted from wool tops (3.15 to 3.40%), the acidity as free oleic acid varied from 6.01 to 12.28, and the oxidised oil acids from 1.02 to 14.61. There were unsaponifiable matters also, and mineral oil is often found on tops. All this shows the great need for work on the subject of wool lubrication in general. Rhys Davies says that the iodine value does not indicate the general tendency of an oil to oxidise ; it shows the final limit to which an oil can be oxidised. The varying amounts of linolic acid glyceride from negligible to dangerous percentages have been shown to be a primary cause of inequalities in the rate of oxidation, from a practical point of view. Pickering stated that linseed oil fatty acids were added by the oil manufacturer to the distillates “ to enable him to carry out his processes more easily.”’

RECENT WORK ON WOOL LUBRICATION.

In the earlier sections of this chapter, allusion has been made to the extremely important work of W. B. Hardy and his collaborators, and a summary of the broad conclusions arising out of the work is given. It is interesting and satis- factory to note that this groundwork is being developed in regard to wool lubrication by Mr. J. B. Speakman, M.Sc., of Leeds University. In conjunction with a student, W. Moe, a study has been made of the relative efficiencies of certain oils as wool lubricants. The work is being continued, but, by the kindness of Mr. Speakman, a summary of the results to date is appended ; the following abstract is taken from the thesis submitted by W. Moe for the diploma of the Department of Textile Industries :— The objects of oiling wool fibre and the properties of a lubricant necessary to these ends are discussed in detail. Good lubricating power, ease of removal, stability, good colour and no staining property, no bad smell and moderate viscosity are the chief requirements. The authors refer to

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the complete absence of previous work on the question of lubricating power of oil in the application to wool. The matter of viscosity is of much interest. If this is too high, the lubricant does not spread well. At normal tem- peratures olive oil has a medium viscosity and good spreading property. Oleic acid, with a lower viscosity spreads very easily, and indeed is considered by some manufacturers “yather On the other hand, with an oil like Castor, some special means for securing proper spreading would have to be employed. The popular impression exists that a thick oil is, per se, a good lubricant, but Hardy has shown that high viscosity does not necessarily mean corresponding lubri- cating power; there is a relation between these variables, . but only in the same chemical series. There obtains, however, a closely accurate relation between lubricating power and molecular weight ; for example, if the coefficient of friction and the molecular weight are plotted, a linear relationship holds. Hardy’s researches point to the conclusion that reduction of friction between two bearing surfaces can be effected by choosing a lubricant of high molecular weight (i.e., having many carbon atoms in the chain), or, by a proper selection of a lubricant with the most effective end groups. The terminal groups must have a powerful attraction for the bearing surfaces, in order to prevent the lubricant being removed from the surfaces. It is known that carboxyl groups (COOH) have such attractions, and hence the free fatty acids—particularly oleic, etc.—are excellent lubricants. Paraffin, a substance devoid of end groups of active properties, has a correspondingly diminished lubricating power. A very significant result of Hardy’s researches on friction is that, taking a series of solids, although the lubricating power of an oil depends on the nature of the bearing surfaces, the relative merits of different lubricants are totally independent of the nature of the bearing surfaces. In other words, if olive oil were found to be a better lubricant than oleic acid for steel, it would probably be a better lubricant on wool as - well; but there may be some reservation for very irregular surfaces like the scaly wool fibre. Coming to the experimental work, some preliminary trials were made, using two surfaces of a beaver-finished cloth, oiled and unoiled, but later rovings were employed, and it was early discovered that the breaking load was considerably greater for the oiled sliver than the unoiled. This might possibly be due to the oil bringing a greater number of fibres into contact, so that the absolute friction could be increased, though the coefficient of friction might be reduced. (N.B.—It is known that in the rope making industry, in making a 3 inch manila

H

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rope, when made in the right way with the correct oil, the breaking strength was 20% greater than when made dry.) Experiments with varying degrees of twist were therefore devised. As the rate of extension of oiled slivers is much greater than the unoiled, the criterion adopted was altered to that of the energy required to extend the roving by a given amount. (NotTE.—The oil was applied by dissolving the 20% of the weight of wool in ether and allowing the solvent to evaporate.) The lubricants were castor and olive oils, oleic acid, and medicinal paraffin. The extensions were in all cases much larger for the oiled slivers, which illustrated the utility of oiling in minimising the breakages in carding. Also, the castor and olive oils give larger extensions than the others. Using the familiar device of estimating the work or energy by the area of the stress-strain diagram, the results of the experi- ments were evaluated and the relative efficiencies of the four media deduced. These were reduced for purposes of com- parison to the dry sliver as unity. The following are the data of a very original investigation :— Castor Oil, 3.29; Olive Oil, 2.72; Oleic Acid, 2.12,; and. Medicinal Paraffin, 1.43 ; compared with dry, taken as 1.00. These are the final figures for the relative efficiency. The restrictions of the insurance companies have compelled attention to the tendency of oils to spontaneous heating, a phenomenon closely connected with their oxidation and formation of insoluble films. In some cases the determination of the flash point is required, the insurance offices regarding as ‘“‘ safe ’’? (and making no extra charge for) very few oils, such as olive oil, lard oil and oleine. A better test from the textile standpoint is some form of apparatus to measure the heating capacity under standard conditions, and the Mackey Cloth Oil Tester has been devised to meet this demand. It consists ot a double jacketed vessel of copper, in the outer compartment of which water is kept boiling. The inner chamber hoids a cylinder of wire gauze, containing a charge of 7 grammes of cotton “‘ wool,” previously soaked in 14 grammes of the oil to be tested, and a thermometer is buried in the mass; means are provided for a circulation of air. The rise of temperature in one hour is noted. A few typical results are given in the appended table :— Temper- ; Tempera- I Tempera-

Oil used. ature in {ture in in 1hr. oe ae 1 hour 15mins. I 30 mins. e.

Olive Oil, neutral I 207°F. I 212°F. I 214°F. I 455°F. 5 hrs. 15 mins. Olein, 97% 206°). I 212°F. ‘| 216°. 4 Saas. 6 ee. 15. mins. Cotton Seed 257°F. I 468°F. — 468°F. lhr. 15 mins. Cotton 4, Olive 4 I 216°F. I 243°F. -— 392°F. lhr. 29 mins.

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SOAPS AND OTHER DETERGENTS.

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CHAPTER. IV.

Soaps and other Detergents.

— ——.

Soaps are second in importance to the scourer and miller only to the water by which they are dissolved. It is possible to apply soap in unscientific and misdirected ways, but it is also possible, even with correct working, to have bad results owing to inferior materials. Hence the composition and manufacture of soaps is knowledge essential to their proper technical application to the fabric. In the strict chemical sense, a soap as a compound of a fatty acid with a base, and the process of effecting this combination is called saponification. Such compounds are strictly analogous to the salts of inorganic chemistry ; they may be prepared by the interaction of the proper quantities of acid and alkali—by heating or otherwise—to neutralisation, as tested by an indicator. This broad definition of a soap is of service to a textile scourer, although in practice the three bases :—potash, soda and ammonia, and the oleic, stearic and palmitic acids compounded therewith, comprise the soaps used as detergents. Yet fatty acid compounds of aluminium are used in water- proofing ; and the fatty acid compounds with the lime and magnesia of hard waters are familiar to the scourer, to his detriment. The reaction between alkali and fatty acid is strictly quantitative. Thus, for the formation of soda soaps from oleic and stearic acids, i.e., Sodium Oleate and Stearate :— I C,,H,,COOH Be NaHO = C,,H,,COONa + H,O Oleic Acid Caustic Soda Sod. Oleate I Water 282 40 304 18 If Sodium Carbonate is used, then :— 2(C,,H,,COOH) + Na,CO, = 2(C,,H,,COONa) Oleic Acid Sod. Carb. Sodium Oleate 2 X 2&2 106 + CO, + H,O Carb. Diox. Water The molecular weight of Stearic Acid baie practically the same :— Canta, ;COOH + NaHO = etc. 40

Se a + Na,CO, = ete.

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Thus it may be said theoretically and very approximately, that Caustic Soda neutralises seven times its weight of oleic acid or stearic acid in forming soap; and soda-ash about five and a half times, all materials supposed full strength. If the fats themselves, i.e., the glycerides, are used, then :— Olein :—(C,,H,,COO),. C,H, + 3Na0H = etc. 884 120 Stearin :—(C,,H,,COO).. C,H, + 3Na0OH = 890 120 etc. ; or approximately seven times as before. It is a frequent and in many respects excellent practice in textile mills to manufacture soap on the spot, either from tallow, or better from commercial Oleic Acid, commonly but wrongly termed Olein. One brand of this substance of about 95°% saponifiable matter, is either treated in the cold with caustic soda solution, or heated by steam jet with soda-ash solution. The maker’s recipe is as follows :—

INSTRUCTIONS FOR MAKING SOAP FROM SOAP OIL. (By courtesy of Price Patent Candle Co., London.) (Oleic Acid, commercial.) To make 50 gallons, take :— 48 gallons water. 12 lbs. Soda Ash. (Brunner Mond Alkali.) 48 lbs. Soap Oil. If open steam is used :— 36 gallons water. 12 lbs. Soda Ash. 48 lbs. Soap Oil. Put the water into a pan or tub of about 100 or 150 gallons capacity ; raise to boiling point), add the soda-ash and_ boil until all is dissolved. Add the oil, slowly and in small quantities at a time, keeping the mixture boiling briskly to keep down the foaming ; continue boiling for twenty minutes after all the oil has been added. The soap solution so made should be dark and free from milkiness. If it is not, there has been insufficient boiling, or too little soda-ash employed. Nore.—lIf the oil is solid in cold weather, the barrel should be placed in a warm place until the oil is melted. Other procedures are sometimes adopted, e.g., Ammonia is compounded with fatty acids forming ammonia soaps. The theoretical basis in the case of Oleic Acid is as follows :— C.,H,,COOH + NH,HO = C,,H,,CO0 + Oleic Acid Ammon. Hydrate Ammon. Oleate 282 3D 299 H,O Water 18

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Ammonium Oleate would doubtless, if the expense permitted, be an excellent textile soap. It has been advertised—and is in use in certain quarters—as a detergent of unprecedented power, and secret formule often involving addition of special solvents, Carbon Tetrachloride, etc., are sold to non-technical mill-owners to be made up on their own premises. It may therefore be worth while to make a comparison costing of Sodium and Ammonium Oleates produced from fatty acid with caustic soda or soda-ash and ammonia liquor.

— oe eee @ ow oe we oe mw ww oe etn ow

ere rs

Fia. 24—Soap PLANT FOR OLEIN SOAP.

CLOSED STEAM COIL DRAINAGE

STEAM

COST PER TON OF SODIUM OLEATE.

1. By caustic soda. 40/322 of a ton of caustic @ £33 = £4.1 282/322 of oleic acid @ £80 = £70.1

Total = £74.2

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2. By sodium carbonate.

106/670 of soda ash @ £83 = £ 1.345 564/670 of oleic acid @ £80 = £67 .343 Total = £68.7 RECKONED ANHYDROUS. COST PER TON OF AMMONIUM OLEATE. I RECKONED ANHYDROUS. 17/299 of NH, @ £25 = £7.08 282/299 of oleic acid @ £80 = £75 .2 ‘Total = £82.3

Notre.—Ammonia liquor; 0.920 at £.25 a ton and one-fifth is ammonia gas. This calculation is, of course, for materials only. But when transport, labour, heating, plant, etc., are taken into the costing, the comparison will not be invalidated. The above calculation, taken from the author’s “ Scouring and Milling,’ Ist edition, 1921, has been left with the original prices, which are of some historical interest ; the conclusion is still true for the decreased costs of raw materials to-day. Lewkowitch’s Theoretical Soap, assuming fatty acids of mean molecular weight 275.

. HARD. SOFT. Fatty Anhydrides 61.60% 38.70% Combined Alkali 7.18 6.84 Water, Glycerol, etc. 31.2 54.60

Actual commercial soaps differ enormously, especially in water content ; super-dried soaps may show up to 88% of fatty acids.

COLD PROCESS FOR SOAP MAKING.

It is quite possible to make soap without the aid of external heating as employed above. In this method the appropriate quantities of fat and alkali—which must be of the caustic kind—are weighed out ; the fat is then added to the dissolved alkali with as thorough stirring as available. If the fat is suitable, the saponification proceeds straight away ; there is an exothermic reaction, i.e., heat is developed by the mutual action of the fat and alkali, and this aids the saponification. Sufficient time, preferably some days, is given for the reaction to complete itself, when the soap may be taken into use. The conditions for successful results by this mode of working are easily perceived. Caustic alkali must be used as against carbonates. Such fats and oils as are approximately liquid at ordinary temperatures, or fatty acids liquid at ordinary temperatures are available. Thus the “ soap oils,” crude oleic

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acid of 95°, saponifiable quality, and cotton-seed oil, etc., are suitable stock for this purpose. The fats rich in the higher melting-point acids, e.g., stearic and palmitic, do not lend themselves to soap making by the cold process. If fatty acids are used, the saponification is likely to be readier and more complete. Clearly, the danger of the cold process is imperfect saponification and the presence of raw fat in the final product. Hence the importance of thorough stirring for emulsification and sufficient time for complete reaction.

Textile Soaps.

The general methods of manufacture of soaps are described in the special technical works on that industry ; some notes on materials are appended to the preceding chapter on Oils and Fats in their textile aspect. The chemical testing of soaps has always been a matter for the qualified technical chemist, and is not less difficult to-day because of recent developments in the utilisation of low-grade oils by the hardening processes. The action of hard waters on soaps, “* lime-soaps,’’ is discussed in the chapter on Water. The particular qualities of soap as a textile detergent per se may now be considered, together with soap adulterations and their effects. The root problem of What is a good detergent ?”’ and its deductions and inferences will constitute a separate discussion of some length and complexity. A textile soap should be of good quality, i.e., the component oils and fats should be good materials; rancid, unsound, impure samples often yield poor lathering soaps and com- municate their offensive smells to the finished fabrics. The particular fat or oil employed in the textile soap is a matter entirely in the hands of the soap-maker, whose judgment is liable to be biassed by the price fluctuations of the raw materials market. The relative scouring powers of the different soap oils or fats is a question which has received little research or technical inquiry. It is discussed to a certain extent in a later section of this book. A large firm of soap manufacturers, setting out a few years ago to supply the wool trade demand, evidently concluded that a tallow basis was, at all events, the fundamentum of a textile soap. It is obvious that where soap must be transported over considerable distances, a hard soap is, if not a necessity, at any rate extremely advantageous. This at once precludes low melting fats and oils for the bulk, e.g., Oleines, which produce soft or pasty soaps with consider- able water content. Where therefore the textile soap is provided by a soap maker, it must almost of necessity be a hard, i.e., a tallow soap ; where soap is made in the mill, the alternatives may be considered on their detergent merits.

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Whatever particular fats or oils enter into a good textile soap, it is essential that the non-alkaline components must be fatty bodies exclusively. Rosin is extensively used in the lower grades. Filling materials, such as Water-glass (Sodium Silicate), Kaolin, Starch or potato flour, etc., must be looked upon as adulterants, and prejudicial rather than mere weighty or bulking substances. Some of these are separately discussed later, in view of the special claims occasionally put forward on their behalf. Most of these substances, on keeping and drying out, have a tendency to effloresce on the surface of the soap, and thus render their presence evident. A foreman scourer, or even the managing director, may wisely examine the bottom of the soap tank now and again between the boiling up of fresh scouring solutions ; soap fillings are occasionally there revealed. A textile soap should contain nothing insoluble; anything of this nature, if thought desirable, is best added separately under control. As regards the alkaline components, a textile soap should not contain excess of caustic alkali any more than it should contain unsaponified fats ; the process of saponification should be complete. Caustic soda—caustic potash in the War disappeared from textile soap making—has an extremely vigorous action on wool, creaming and harshening it in quite small concentrations ; when used in a scouring department, it should be employed intentionally, and in known quantities. Its detergent qualities as compared with the carbonate, receive treatment separately. The perfect neutrality of a soap for scouring purposes is a point upon which there has been some over-insistence. Textile soaps are almost invariably employed with the addition of alkali—ammonia, or usually soda-ash—often in great excess ; to insist on the close neutrality of the soap under these circum- stances is scarcely rational. At the same time, the soap maker must not be allowed to use soda-ash as an adulterant ; the safety of permitting an excess of sodium carbonate is one of the chief inducements to soap making in the scouring shed ; little risk is run of sending forward to the soap tanks any unsaponified fats. Mere excess of soda in a soap, provided > that it is not a cheapener, is not injurious ; alkali, either in the soap or added with it, is necessary for the saponification and emulsification of the free fatty acids of the spinning oils. A related delusion has long persisted (and is only partly dispelled by the experiences of the war period) in favour of Potash v. Soda soaps. Manufacturers have been known to assert that it was possible to obtain their own particular high- class finish and handle only by the use of potash soaps, when their scouring department was working these soaps along with

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10°Tw. solutions of soda-ash ; and possibly milling their cloths by soap jellies of hard white filled curds. What scientific principle has failed to accomplish, the stern necessity of the War has brought about. Potash salts being unprocurable, alternatives have been employed, and succeeded. Incidentally, it was well understood in the proper circles that the soft soaps were the very focus of adulterations. Another fallacy in the potash soap preference lies in the fact that they were generally made from low melting fats and oils, and these have superior washing powers at the low temperatures, and are more easily washed out. The original olive oil soap is a case in point; the later use of linseed and soya-bean oils of titre 18°-20°C., and the employment of castor oil of titre 2°-3°C., are sufficiently indicative of this aspect of the question. A less prevalent, but still existing, delusion is that concerning the superior nature of Marbled or Mottled soaps, in which the impurities from the raw materials and the soap lyes constituted the mottling. Such soaps, when containing an excess of water, will not mottle ; hence the tradition of their superior value. The old Marseilles soap, made from the poorer qualities of olive oil and a crude soda, was a mottled soap. At the present time, mottling means nothing—or positive adulteration by mineral matter. As a rule, the lower the melting-point of a fat or oil, the greater is the proportion of the lower m.p. fatty acids; the oleates, linoleates, etc., as against the stearates, palmitates, etc. Now it is becoming more recognised that the solubility of the soaps from low melting-point fatty acids is greater, i.e., the oleic acid soaps are more soluble at ordinary temperatures than those containing principally stearic and palmitic acids and the like. Therefore, for much of the usual run of work of the scouring shed, the former are to be preferred. Sodium stearate—hard white curd soap—requires a comparatively high temperature for its best working, not far from the boiling- point of water. Again, the order of solubility of soaps in respect of their bases is Ammonia, Potash, Soda. But the gain of solubility by the use of potash over soda is hardly worth purchasing at the increase of cost ; more is obtained by proper choice of the fatty acids. In the case of a household soap, which in ordinary use may be employed for washing the hands in cold water or boiling with garments in laundry work, a mixture of fatty acids is desirable. But the requirements of textile scouring are more restricted and specialised, and may be more accurately met. Again, soaps of the higher fatty acids are more sensitive to “‘ salting out ”’ in alkaline solutions such as are the normal practice in textile scouring. The soap maker, being well aware of this property, makes his soaps by successive

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additions of alkali of relatively lesser concentration, and thus maintains continuously that condition of general emulsification which is the primary requirement of soap manufacture. Perfect emulsification is also fundamental in scouring, and all factors should be assembled to secure this. An interesting case from the author’s consulting experience illustrates several points dealt with in the present chapter. A firm of wool scourers in large practice used as detergents in the wool bowls ordinary Brunner Mond soda-ash with two soaps. One of these was an imported American cotton-seed soap made from ‘foots,’ of low grade and badly-smelling. The second was made on the premises from caustic potash and a soap oil. Incidentally, the firm stated that originally they had bought solid caustic potash, but, owing to the trouble experienced in dissolving it (?), they now purchased it ready dissolved to a 20% solution. As this was delivered to them several miles from warehouse, the increased cost may be imagined. The oil was purchased as a “soap oil.” The potash-oil soap was made in an ordinary iron pan in batches of approximately 2 cwts., once or twice per day, and used immediately and from day to day as required. <A quantity of water was run into the pan, potash solution added and steam blown in to boiling; the oil was then added, bucket after bucket, steaming and some stirring being continued for twenty minutes. The resulting solution was put into use, if wanted, straight away. The effects noticeable in the wool bowls were lack of scouring power with poor lathering, and imperfectly cleansed greasy handling wool, dull and lacking in lustre. Previous results, using a well-known soap oil high in free fatty acids, had been more satisfactory. The errors of practice and bad technique are fairly obvious. The mixing of a good potash soap with a low grade cotton ‘foots’ soap in the same scour is neither logical nor economical, especially when soda ash of 3-4% is also present. The making of soap by these rapid methods necessitates abundant free fatty acid in the oil; the “‘ soap oil’ in question was largely of a neutral type. The alkali, i.e., potash solution, was over- diluted by starting up with additional water. Hence all the conditions tended to incomplete saponification, and this was accentuated by taking the product into immediate use. In the bowls it liberated unsaponified fat, failed to lather or set up a real emulsion, and the evils followed. When the potash solution was used undiluted, the oil added more slowly, with better stirring and proper time allowed for perfect saponifica- tion, a good freely lathering soap resulted. It may be mentioned in passing that the practice of mixing a high grade and a low grade soap is quite common in textile works, and it would be interesting to know on what principles—

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either of efficiency or economy—it is based. In many cases the type of soap employed is governed entirely by the question of cost, being what ** the goods will bear,” or less! No single kind of soap can meet, either theoretically or in practice the variety of application met with in scouring, raw wool, fine worsteds, cottons, good woollens, low woollens, etc.; and further, in milling, in the degumming of silk or other special operations. It has been quite usual either to buy on a guarantee, or alternatively to secure by chemical analysis a soap with, say, 63°% of fatty acids ; and to accept this as the end of the matter. Commercial “ genuine’’ soaps contain about 63°% of fatty acids on a weight of 68-69% of perfectly dry soap, thus giving approximately 30°% of water. Soaps are now made by a process of. chipping in “ flake”’ form, and are super-dried to a water content of about 12%, with a corresponding rise in the fatty acid percentage. It is difficult to persuade many users that such soaps are essentially the same—on the actual dry soap basis—in respect of fatty acid, and that their merits must be assessed on other considerations, e.g., lessened cost of transport, ease of solution in the soap tanks, difficulty of theft by employees, etc. There is great need for wider knowledge in textile works regarding oils and soaps and their application. Hardness in a soap may be due: to drying out, an excellent fault from the buying point of view, but it may be also due to a chilling process during manufacture or to a selection of high melting-point fats not necessarily most suitable, or to adulteration by “ fillers.”” Whiteness may be secured by pickling the soap in brine. A badly saponified soap is soft, quickly goes rancid, sweating in storage. Excessive additions of alkali or silicate of soda cause a soap to effloresce on keeping, i.e., powdery deposits form on the outside of the bars. Resin soaps are invariably discoloured to yellow, brown, or gray shades. I

On Special Detergents.

In the textile industry there is always existing a strong advocacy of new detergents. The peculiar difficulties of the scouring process are continually being increased by the use of new fibres and lubricants, often of inferior kinds ; and on the other hand there is always the inducement of achieving results by quicker and more effective methods. To these is to be added the invariable claim of cheapness with efficiency. Most of the recent introductions of these substances fall into one or other of the following classes :— 1. Fuller’s earth and allied bodies. 2. Cereal soaps and products of alkaline action on proteids. 3. Solvents ; mainly organic, for direct removal of grease. 4. Detergent Powders; usually based on soda and soap powder.

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FULLER’S EARTH, &c.

The fuller’s earths are fine clays, generally non-plastic, of varying colour, usually bluish. Chemically they are hydrated Aluminium Silicates with several per cents. of oxides of iron, lime, magnesia, etc. Their characteristic property from the textile point of view is that of absorbing grease, but they are also used for filtering oils. A report by the Imperial Mineral Resources Bureau gives full information regarding the geology, chemical composition, and occurrence of the British deposits. Historically, clays were used for cleansing before the invention of soaps, and the use of fuller’s earth as a detergent is an old expedient in the industry. It is still a resource for difficult goods or as a cheap scour, e.g., on the so-called low worsteds, of cotton and recovered wool. One of its principal uses to-day is in the washing-off of indigoes, logwood blacks, and wood colours, in which its gentle frictional qualities are seen to the best advantage ; quillaia or a saponin extract are often added to this bath as foam producers. Whether fuller’s earth and similar substances remove grease from fabrics other than by friction is an unsettled question ; the claim for certain of these bodies is that they have special adsorptive properties for fatty matter. Examples of such materials are China clay or Kaolin ; Tale or Soapstone (powdered Stearite) ; Killas, an argillaceous schist ; Pumice dust, etc. The modern development of these consists in attempts to bring them into the colloidal condition by the due addition of sodium carbonate, gelatine, blood serum, etc., to their aqueous suspensions. It has been proposed to use Aluminium Hydrate directly on similar grounds. It would appear that direct absorption on the surfaces of specific materials occurs in certain operations, e.g., in purifying and decolourising processes. Thus the fuller’s earth used in refining petroleum distillates tends to retain the unsaturated hydrocarbons and the sulphur compounds selectively, and a pseudo fractionation of some components also happens. If fuller’s earth be shaken with water and then filtered, the filtrate is neutral to litmus paper or to phenol phthalein, showing that no soluble base or acid is present. If fuller’s earth be shaken with a sodium chloride solution and filtered, the filtrate is acid to litmus or to phenol phthalein. This is because the fuller’s earth has adsorbed the base. If one presses litmus paper against moistened fuller’s earth, the litmus paper turns red, and if one adds fuller’s earth to a faintly alkaline solution of phenol phthalein the red colour disappears. This is not because the fuller’s earth is acid, but because it takes the base from the sodium chloride, the litmus, or the phenol phthalein. (Bancroft.) Fuller’s earth was historically earth used in the fulling process, i.e., what is in modern language termed “ milling” ;

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though the old fulling operation was a combined scouring and milling process, such as is still used in the more primitive corners of the textile trade, rough tweeds and kerseys, home- spun blankets, etc. This question of its preferential adsorption for dirt and greasy matter arises also in the case of Kaolin or China Clay, and numerous efforts have been made in recent years to introduce similar detergents into textile practice. It is therefore opportune to give a thorough discussion to this particular aspect of the detergent problem. New develop- ments in the art of cleansing must and will arise in the progress of applied science, either by the discovery of substances with special adsorptive powers, substances with greatly reduced surface tension, or in other ways. In this present application of very fine powders there has been a proposal to use very highly ground slate in place of fuller’s earth, which in rather limited trials utterly failed; it appears that such powders must show some approximation to the colloidal state. Certain American clays of allied type, ‘‘ Bentonite,’’ have been brought forward. said that this succeeded in the difficult technical problem of de-inking, in a weakly alkaline solution, the pulp of old newspapers. More extensive trials have been made with China clay. This substance is the Kaolin of the Cornish quarries and is in the purest forms, a silicate of alumina, hydrated and in an extremely fine state of division. Alkalies, such as caustic soda or ammonia, tend to peptise the clay, i.e., to bring out the finest disintegration, even to the colloidal state ; a mass of China clay, when left covered with water, will in time fall to pieces. Kaolin has long been used in soaps as a filler, but it possesses some cleansing power. Any inert powder which makes the interface between two liquids more viscous tends to favour emulsification and confer stability. E. Weston has carried out many experiments on the use of China clay in the saponi- fication of oils by alkali, and on emulsification of oils by the addition of China clay to soap solutions, etc. It is claimed that soap and clay produce :— 1. A greater lowering of surface tension against air than a solution of soap alone. 2. Increased lathering properties. 3. Greater absorptive power. 4. Greater detergent power. Some of these criteria are merely alternative statements or consequences of the others, but it seems established that there is special detergent property. Whether this is generally available in the washing of textiles—fibres or fabrics—is. another question. An important question with regard to all these insoluble materials and which arises also in the case of silicate of soda, is the possibility of residual matter left after

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the scouring. Such dusty material in dried wool would be very prejudicial in the oiling for yarn making, and objectionable in dyeing, leading to loose colour; it is injurious also in finished fabrics. These preparations are apt to separate out in the soap tanks and the scour and leave precipitates ; there follows great irregularity in the scouring machines and risk of damages. In a case known to the writer, the scourer’s 5°, soap tank showed three inches of white mud at the bottom, where the China clay had precipitated. Another preparation, claiming to be based on the detergent properties of borax, proved on chemical analysis to have less than 1% of boron compounds, the bulk being ordinary soda-ash with a soap powder! It is perhaps rendering a service to the textile industry to warn manufacturers and their scouring staffs, and to recommend caution in taking for granted the assertions of skilfully drawn advertisement circulars. A comparison of many such shows that all their compounds fulfil completely the following desirable objects :— 1. Degreasing the wool or fabric, without felting ; producing lofty and soft handle. Lead to better spinning and do not attack the fibre ; free from caustic alkali, and of a neutral character. Kither lather very freely, or, if they do not lather, then lathering does not matter. Are invariably extremely economical, saving soap in all degrees up to 50%, or even two-thirds. Are especially effective against mineral oil and un- saponifiable matter. Do not affect colours, but produce brightness and lustre. Shorten the scour; are not affected by hard waters, and are proof against calcium and magnesium soap forma- tion, etc., etc. As the art of scouring has not yet reached either perfection or finality, it will be well to exercise judgment rather than faith ; the style of certain trade circulars in this connection is characteristic of the patent medicine literature rather than that proper to a difficult and exceedingly technical operation.

CEREAL DETERGENTS.

Another class of special detergents is apparently founded upon the familiar “‘ oatmeal soap ”’ of the toilet table. It is perhaps a fact that almost any inert substance in a fine state of subdivision will exert some detergent power, if only of a mechanical kind ; and it is an easy transition from the natural clays to powdered cereals, and thence to chemical action upon these with a view to the production of new cleansing materials. One of these is the substance known as “Sapon.” This is

2 3.

or +

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stated to be prepared by treating maize meal with caustic soda. Other suggestions have been made regarding the products of alkaline reaction with proteids, e.g., sodium caseinate (Cf. p. 61). Solutions of Sapon undoubtedly display much “ surface activity,’ as tested by the drop pipette (See Shorter, Jour. Soc. Dyers & Cols.). It must be noted that, as commercially supplied, Sapon contains a percentage of ordinary soap, though this, it is stated, is added as a concession to the popular prefer- ence for a lathering detergent. Obviously, a product of this kind stands in an entirely different relation to the lime and magnesium salts of hard waters from the alkali-fatty acid detergents, and it cannot be judged by a comparative chemical analysis. It would be interesting to examine all products of this type by a preliminary dialysis to separate the colloidal and crystalline components without chemical decomposition ; the dialysed and non-dialysed fractions might then be chemic- ally examined (Cr. Section on Formation of Foams).

DETERGENT POWDERS.

In general, the basis of most of the compounds of this type offered in the textile trade is ordinary soda-ash ; the next bulk component is usually a dried and powdered soap. . A further common addition is ordinary borax, sodium borate. To these may be added inert powders of the type dealt with in the section on fuller’s earth, kaolin, talc, etc. There may be agents of a bleaching type, e.g., Perborate of soda, which is one of the most stable of the per-salts. Frothing capacity is sometimes given by Quillaia or its extracts (Saponin). Starch or cereal flours may be present. In certain cases some gela- tinous or gummy constituent has been added, perhaps with a view to “ protective colloid’ action. Free caustic soda is a favourite component, for obvious reasons. I

SILICATE OF SODA.

or “ Water-glass,”’ is extensively used in soaps. The definite chemical salt crystallises with nine molecules of water as Na,SiO,, 9H,O; it melts at 40°C. in its own water of crystallisation, and is easily decomposed, even by the Carbon Dioxide gas of the atmosphere. The commercial forms all contain excess Silica, even up to four times the formula quantity ; this gives these products their colloidal properties. Solutions with high silica content can be concentrated to jellies having about one-third solid, two-thirds liquid. The viscous liquids are relatively more alkaline, containing nearly two- thirds of total solids. Commercial solutions are supplied with densities ranging from 69-184°Tw., or one-third to two-thirds solids. The anhydrous material is difficultly soluble. The boiling and freezing points of sodium silicate solutions indicate

I

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their colloidal nature, being little different from those of water itself. Sodium silicate is completely hydrolysed in hot dilute solutions, and for washing purposes is then equivalent to a solution of caustic soda. Used in soaps, it is apt to deposit silica in the fabric. Kind (Wirkung der Waschmittel, 1910) washed cotton and linen thirty times with 2% water-glass of 69°Tw., and found ash residues up to 14%. Pennington proved precipitates of amorphous silica in yarn. Iron is a regular impurity in silicate of soda. Soaps prepared with silicate of soda may contain up to 50% of water. On the whole, the use of this substance in textile soaps must be re- garded as an adulteration. The German technical journal ‘* Der Textil-Chemiker und in discussing the influence of Silicate of Soda in washing, states that :—

‘“'The use of hard waters in the washing of textiles may produce un- pleasant end results. When only such waters are available it is the custom in some instances to add a proportion of silicate of soda to the washing liquor with the object of softening the hard water. Besides adding to the cost of the soap, soda, and per salts employed by laundries, silicate of soda not only also seriously affects the quality of white materials but imparts to them a noticeable degree of harshness. Under certain conditions water glass yields colloidal silicic acid which in the circumstances connected with the operation of washing may become attached to the material treated, and upon drying may be present thereon as a white somewhat gritty powder, which is not readily removable. The damage it may cause to the fabric may be solely of a mechanical order. A method designed (Ger. pat. 316,293/1917) to prevent any such damage to fabrics by water glass, in the course of washing, recommends the treatment of the material after the washing with a dilute solution of ammonium chloride or other ammonium salt of a strong acid. This reeommenda- tion does not appear to be based on good facts. In analytical chemistry it is well known that ammonium chloride and the ammonium salts of other strong acids precipitate the silicic acid of water glass, in the form of the hydrate. Although this reaction may not take place quantitatively in conformity with the equation representing the reaction, it takes place sufficiently to admit of determining quantitatively the presence of SiO, on the treated material. The ammonia set free is not equal to bring into solution again the pre- cipitated silicic acid. It has been shewn that 100 parts of a 10% solution of ammonia dissolves only 1 part of silicic acid freshly precipitated from water glass, and only 0.3 parts of the dried precipitate. Details are given of the results of a number of experi- ments carried out, which lead to the conclusion that silicates should not be used at all, and: to the recommendation than an extra amount of soda and soap should be employed with the use of hard water in the washing of

The ready decomposition into colloidal silica and caustic soda brings this substance into the scope of the discussion on China clay above. There is undoubtedly some detergent power in silicate of soda, but it is probably of a kind better directed to domestic than to textile practice. The scouring of woollen fabrics has been actually performed in one factory by a combination of water-glass and stale urine, and excellent

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results were claimed for the method ; after all, scientifically, the scour was an alkaline colloid. Certainly, the combined colloid and mildly alkaline nature of silicate make it an excellent neutraliser for the peroxide bath in bleaching. But on the detergent side, it appeals more strongly to the maker of soaps rather than to the user, just as in the case of resin. A manu- facturer of silicate its employment to soap makers in the following terms :— I ““General household or laundry soaps should have several special qualities. They should have sufficient “strength” or cleansing property to act readily on the grease and other dirt which they are ordinarily used to clean, but should not be so strong that they will injuriously affect the hands, or fabric or their colours. They should dissolve easily in water, but even in hot water the cakes should not become so soft that they will be used wastefully. They should be as inexpensive as possible. Silicate of soda properly used helps to give soap all these qualities. Silicate of soda is a mild alkali, and is, therefore, itself a cleanser. in some laundries a certain amount of silicate is regularly used in the washers. The addition of silicate to soap adds to its cleansing power. A soap containing silicate makes up into firmer cakes than if made without silicate, and the cakes last longer in use. They do not soften down in hot water so much, and there is therefore less waste and greater satisfaction to the soap user. Silicate of soda is one of the least expensive of all the ingredients that go into soap. It, therefore, brings down the average cost of the soap. Silicate is, in fact, the main thing that makes it possible to have inexpensive household soaps.”’ Kramer (Kolloid Zeitung, 1922, p. 31) found that a fine stable emulsion was formed when a plant or animal oil was added to a 0.2% Sodium Silicate solution, the emulsion showing Brownian movement. He states that the free fatty acid of the oil combines with some sodium, liberating silicic acid, which acts as protective colloid.

QUILLAIA (Soap or Panama Bark)

is the bark of a rosaceous tree, possessing the property of causing frothing in water extractions. The extracts contain ** Saponin,” an amorphous white powder, capable of foaming even in solutions so dilute as 1 in 1000; the froth is very persistent, but dispersible by alcohol or ether. The commercial article is obtained by exhausting the powdered bark with water, evaporating, and boiling the extract with alcohol under a reflux condenser when the pure saponin is obtained. In the works the powdered bark or its water extractions are used as a frothing agent where soaps are inadmissible.

BORAX,

or Sodium Pyroborate, Na,B,0,, 10 H,O is a natural product ; colourless crystals with an alkaline reaction, or as a white powder; soluble in cold water about 1 in 20; in hot water

a

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2 in 1. A mild alkali, but too expensive for ordinary use.

Used for the preparation of perborate of soda for bleaching purposes.

‘* PERSIL.”’

According to the ‘‘ Textile Mercury,” 1909, Nov. 6th, this is said to be Soap, 20%; soda, 33%; silicate of soda, 7% ; perborate of soda, 10% ; and water, 30%.

‘**A HOUSEHOLD WATER SOFTENER ”’

was composed of 70 parts Diosodium Phosphate, 20 parts Borax, and 10 parts Sodium Carbonate.

‘* FELS-NAPHTHA.’’

Dr. Bela Lach, in the Siefen. Ztg. 192, 125, gives this as containing Benzine 10-15%, of high boiling-point, and the raw materials as cotton and corn oil; there is a relatively small proportion of hard stock, such as tallow or palm kernel oil, some hydrogenated oil. Another analysis gives 10° petroleum naphtha with a rosin soap mass added to common soap.

Solvents.

i.e., grease solvents. The spinning oils being, after all, the principal “‘ dirt’ of a fabric, it is to be expected that direct attack upon them will be a favourite method of detergent action. The number of solvents of fats and oils in organic chemistry is large, and it is instructive to discuss their advantages from the textile standpoint. The question of their employment in a soap-alkali scouring medium is a separate matter. The following table gives the properties of the principal solvents available for textile purposes, either as stain-removers or as additions to the scour :—

BOILI ECI caret? omens ae Cent. hal./gm. Ether 34.6 0.53 90 Carb. Disulphide 46.2 0.24 83.8 Chloroform Sri2 0.23 58.5 Alcohol meth. sp. 0.6 205 Carb.Tetrachloride 76.74 Benzole pur. — 80.3 0.41 93.4 Benzole commer. ica 0.408 95

Trichlorethylene 87.4 Tetrachlorethane 147 Petroleum Spirit 90-110 0.454 Turpentine 159 0.41 74

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Many of these substances are highly inflammable, the leading exceptions being the chlorine derivatives ; some, especially these latter, are injurious to health if inhaled. The chlorine compounds as a class are liable to decomposition, rusting the container or other ironwork. Being concerned here mainly with their use as detergents, the properties of miscibility and specific gravity are important. Alcohol is miscible in all proportions, but the others for this purpose are virtually insoluble. This miscibility is secured in some instances by emulsifying the solvent, a favourite agent for this being a sulphonated oil. The employment of this class of additions to the scouring medium is extending rapidly, and it is desirable to discuss the matter as fully as theory and the results of experience may permit. Among new bodies of the ‘“ solvent ”’

type developed in recent years are certain chlorine derivatives of Ethane and Ethylene :—

SPECIFIC BOILING GRAVITY. POINT. Tetrachlorethane C,H,Cl, 16 147°C. Pentachlorethane C, HCl, ror 159°C. Dichlorethylene C,H,Cl, 1.25 55°C. Trichlorethylene C, HCl, 1.47 88°C. Perchlorethylene C,Cl, 1.63 121°C.

(Gustav Koller.) Of these, the first, Tetrachlorethane, is being extensively introduced into the wool industry as an aid to scouring. It is a clear liquid of characteristic smell resembling that of chloro- form ; its vapour is slightly poisonous, and indeed dangerous in excess, having been responsible, when used as aeroplane dope during the War, for some deaths. It is soluble in water or ordinary scouring media only to a small extent, and rather more miscible in emulsions; but excess, owing to the high density, quickly settles out at the bottom. As supplied in the usual iron drums, it may contain some water with danger of rusting. I The name “ SOLVENTS ” as applied to these and analogous substances, is certainly misplaced in the detergent aspect. Every member of the general list above is, in greater or less degree, an active solvent for oils, fats, resins, gums, and similar bodies, but the action in scouring cannot be a matter of direct solution only. In an ordinary woollen scour of four pieces there may be 30 lbs. of wool oil to be removed from the cloth in the ratio, say, of 25 lbs. olein to 5 lbs. mineral oil. Additions of solvent to scours are usually of the order of 3-1 pint. Without pushing the discussion too far, it is surely impossible for a pound or so of solvent to exercise much direct dissolving action in a case of this kind. The author, in recent lectures, has pointed out a property of many of these bodies which is

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probably more potent in its effects than the solvent action, viz. :—the reduction in surface tension which occurs in the ordinary alkali-soap scouring medium when even small quantities of these substances are added. This phenomenon is easily demonstrable by experiments on soap bubbles, on the scattering of powders floating on the surface of the liquid, on the disruption of floating oil films, or more exactly by surface tension apparatus such as the Drop Pipette, etc. In the general table, alcohol is miscible with water in all proportions without after separation ; ether has a solubility of about 8%; all the others are practically insoluble. This requires that, as additions to the scouring bath, they must be carried in an emulsion, an operation effected by various means, of which the following are examples :— 1. Use of a strong soap solution or soap paste. 2. Blending with sulphonated oils. 3. Admixture with alcoholic solution of soap, etc. All these and possibly others are employed with the favourite solvent of the day :—Tetrachlorethane, the characteristic smell of which reveals the nature of the compound without exact chemical analysis. I An interesting experiment on the properties of certain solvent bodies is given herewith :—A drop of chloroform or carbon tetrachloride is placed on the bottom of a glass dish and water or dilute acid poured over it; the drop is well rounded. When the solution is made alkaline, the drop flattens out. Ordinarily, this would mean a direct lowering of the surface tension of the water phase, but it is further found that if sodium chloride is present, the effect of the alkali is the same. Now the addition of salt increases the surface tension of the water phase. What really happens is that hydroxyl is adsorbed at the interface lowering the surface tension and causing the organic liquid to flatten. A conforma- tion of this is seen in experiments by Von Lerch on the surface tension between benzene and water. Benzene and pure water gave a value 32.6 at 85°C. With M/4 caustic soda this dropped to 20.7, and with M/2 ammonia to 27.3, the difference being due to the greater ionisation of the soda. Also, in experiments on mobility it was found: that drops of benzene in caustic soda moved readily under electrical stress and hardly at all in sodium chloride or hydrochloric acid (Bancroft). It is thus evident that these organic solvents may show effects in scours other than simple dissolving power. It is easily possible for the scouring department to purchase its own solvent direct and mix it on the spot. There are at least a dozen preparations on the market based on Tetra- chlorethane, for which the most extravagant claims are made, and a huge mass of pseudo scientific statements put forward

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in support. It is probably the best principle that the scourer should know exactly what reagents he is applying to the wool or cloths ; it is then likely that the results will be more under control. There is little information available respecting the general properties and detergent action of these “ though it is probable that advances in scouring might be made along these lines. The matter should be taken up by one of the Research Associations connected with trades employing detergent materials, e.g., Wool, Cotton, Silk, or Laundry work. Information is needed regarding the solubilities and misci- bilities of these bodies with water, scouring media, and with each other; their efficiencies in purely solvent action and in lowering surface tension, particularly interfacial tensions ; the best modes of preparing them for addition to scours; the possibility of other organic liquids being utilised in this direction, etc. At present the subject is a mass of special details without much general principle. Alcohol is a good general solvent, mixes in all proportions with water, but is comparatively ineffective on mineral oils, one of the commonest of scouring impurities. Benzol is insoluble in water—or nearly so—is a good solvent for mineral oil, but does not work well in damp or wet materials. The extreme volatility of ether, carbon disulphide, and petroleum spirit rule these out, except where specially devised plants are employed. Further, most of these substances have vapours which are more or less poisonous. Carbon Tetrachloride, which was the earliest of the aids to scouring and is still one of the best available, is objectionable in this respect, and benzene also. Cresol has been added to soap apparently with advantage, but cases of after-smell developed in the goods have occurred ; obviously a pronounced odour of disinfectant in the merchanted cloth would raise doubts as to the quality of the raw materials. A newer development in the phenol-cresol direction is stated to have arisen in Germany. Carbolic acid or phenol has long been added to soaps as an antiseptic, but hydrogenated phenols or cresols have now been produced and added to soaps, with the direct intention of dissolving hydrocarbon oils. Cyclo- hexanol (Hexahydrophenol) C,H,,OH obtained in this way is said to be a suitable addition to soap, having good lathering properties and capable of emulsifying mineral oils. Cyclo- hexanol from phenol boils at 160°C. and has a specific gravity of 0.945, being, it is said, readily miscible with water. Similar bodies result from the hydrogenation of cresols. There is great confusion in the nomenclature applied to these bodies. Strictly speaking, benzine is a product of the mineral oil industry, as are also gasoline, petrol, petroleum spirit, and petroleum naphtha; while benzol and

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solvent naphtha are derived from the coal-tar series, and the spelling benzene should denote benzol. The petroleum benzine is a water-white liquid of s.g. 0.73-0.78, b.p. 120-150°C., and is an excellent solvent for all oils and greases ; from it are compounded benzine soaps for dry cleaning. Oleates of both the ordinary alkalies and of the alkaline earths (e.g., magnesium oleate), are dissolved in benzine, or corresponding compounds are prepared from oleic acid, with ammonia, caustic potash or soda, and alcohol. These are variously termed saponoleines, saponines, etc. The true saponin is the glucosidal extract of soap bark (Quillaia) referred to above. Dekalin and Tetralin are really hydrogenated naphthalenes, but the latter term, in various modified spellings, is applied to preparations of carbon tetrachloride and tetrachlorethane in trade circles. Another novel detergent of recent German origin is B-tetralin sulphonic acid in the form of alkali salt, which, it is asserted, in proportions of 15-20% of a soap powder greatly increases the lathering qualities. Octo-hydroanthracene sulphonates behave in the same way. It would seem that the sulphon radical will have to be regarded as the distinctive detergent group. Yet another is the sodium salt of toluene chlorsul- phamide. The Badische Co. have patented the use of certain propylated aromatic sulphonic acids as substitutes for soaps and Turkey red oils. Trichlorethylene has been accused by the laundries of giving a grey tint to goods after a few washings.

SULPHONATED OILS,

or Turkey Red oils, enter into a number of detergent compounds. The origin of these bodies was probably a rancid olive oil, but they are now prepared by treating various oils at low tempera- tures with strong sulphuric acid, slowly added (drop by drop). The best Turkey-red oil was sulphonated Castor oil, but olive oil and oleic acids have been used: even cotton-seed oil for cheapness. The usual commercial Sulpholeates contain 50-80% of sulpho compounds, the rest being water. The products are neutralised after the interaction, and various methods of separation and washing are employed. Their usefulness in the detergent aspects consists in their strong emulsifying powers; sulphonated castor oil, neutralised by caustic soda or ammonia or both, is a general emulsifier for water-immiscible solvents. A discussion of Sulphonated Oils, by Radcliffe and Medofski, with a full bibliography, will be found in the Jour. Soc. Dyers & Cols. for Feb., 1918. It is not difficult to prepare sulphonated oil or “‘ soluble oil ”’ in the works. Strong Sulphuric acid of 168°Tw. is slowly added with constant and thorough stirring to four times its quantity of castor oil, the mixture being well cooled by putting the reaction vessel in water maintained at 30°C. or less. Lack of

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cooling produces a dark-coloured result. A small quantity of water is then added and the mixture allowed to stand, when separation into two layers occurs; the lower, consisting of spent acid, is drawn off. Washing with a saturated solution of Glauber’s salt follows, to remove the excess of sulphuric acid. If the operation has been properly carried out, a few drops of the sulphonated oil mixed with a little dilute ammonia will dissolve to a clear solution. The oil is finally carefully neutralised by ammonia or sodium carbonate until a clear solution is obtained on dilution with a small quantity of water. If emulsified oils are desired, the process may be varied after the washing from excess acid, by the addition of the required amount of other oil, and treating the mixture with caustic soda; saponification then occurs and a permanent water- soluble emulsion is formed. Monopol oil is said to be made by boiling a sulphonated oil with water, and mixing the fatty oxy-acid with a further quantity of castor oil, heating, and after cooling again, sul- phonating with sulphuric acid; washings with water or alkaline water to neutrality follow. It has a higher percentage of fats than Turkey red oil, 50-75 against 30-50. It has great solubility in even cold water, and is an excellent penetrant, as in cop dyeings, used as one pint to 100 gallons. Sulphonated oils exhibit, like the true soaps, great powers of reducing surface tension, dispersing and emulsifying even mineral oil. They show exceptional penetrative powers which have sometimes, by reason of irregular application, caused trouble in uneven dyeing. Besides their utilisation in the dyeing of Turkey red, they are employed in wool creams for spinning, and as emulsifiers for various organic solvents. They are, perhaps unwisely, added to conditioning water, and have been regularly used in some mills in the milling operation instead of the usual soap solutions, in this case probably with an idea of protecting the colours. A good “soluble”’ oil, when diluted with ten times its own volume of water and allowed to stand for several hours, should show no separation ; or even on gentle boiling. It is possible that sulphonated oils, as additions to scours, would be as useful, and perhaps more useful, than many solvents.

TWITCHELL-TYPE SAPONIFIERS.

The aromatic sulphonic acids are quite comparable in acidity to the strong mineral acids such as Hydrochloric, etc.; the physical resemblance to the oils is due to the presence of the. higher fatty acids in the nucleus, conferring an increased solubility, with emulsifying and foaming properties in water. They formed the original Twitchell reagents for the saponi- fication of glycerides ; by their use, low grade materials such

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as garbage grease or oil-foots are used as raw stock for fat- splitting ; a fractional distillation of the fatty acids to improve colour and odour follows. These fatty acids are then directly employable with the cheaper form of alkali, soda-ash, for production.

SULPHONATED OILS AND HARD WATERS.

A feature of products based upon sulphonated oils is the relative freedom from interference by the Calcium and Magnesium salts of hard waters in detergent processes. Pomeranz (Chem. Ztg., 1916, p. 244) says that all sodium salts of higher fatty acids possess the power of dissolving limited amounts of fatty acids. He ascribes the virtues of the sulphon- ated compounds to their emulsification of the calcium soaps, (Cf. note on protective action of the scour against hard water.

p. 138).

TETRAPOL SOAP S.S. FORMULA. (Bayer Co.)

Monopol liquid, 45% fatty acid 3310 kg. Water 3223 Carbon Tetrachloride 1493 Marseilles soap, 63°% fatty acid 800 Castor oil soap, 60°% fatty acid 800 Perfume (Nitro-benzol) 6 Alcohol 7 144

99 3? 99 39 33

99

Monopol soap is a sulphonated castor oil neutralised by caustic soda.

Attempts are now being made to utilise the Sulphite cellulose residues from the wood pulp industry as detergent materials : ‘* Protectol ” occurs in both liquid and powder forms and may be used in quantity one-half as much as the soda ash taken. 1 to 5% retards the felting of wool, for example, in hank dyeing. It is stated that among substances under experiment or being employed, are certain Syn-tans, Lecithin, Taurocholic Acid (Ox-galls), and some dispersing agents. As wetting-out agents, there are recommended Nekal A or Oranit F in scouring and as additions to oil emulsions in spinning. A summary of the organic solvents would include Pyridine and Pyridine preparations, e.g., Tetracarnit, Hydrogenated Phenols, such as Cyclohexanol, Hydrogenated Naphthalenes, e.g., Tetraline ; Halogenated Paraffins, e.g., Carbon Tetrachloride and Tetra- chlorethane, etc.

Horsfall and Laurie, examining solvent detergents, find that on dilution, the solvent power on fats and oils is rapidly

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diminished or lost ; in general, solubilising power quickly falls on dilution. Farrow and Neale give a curve showing the reduction of surface tension when Cyclohexanol is added _ to water.

THE FOAMING OF TEXTILE SOAPS.

Kind and Zschacke (Textilberichte) found that Marseilles soap produced the greatest amount of foam, then palm oil and tallow soap, then solid potash soap, and last of all, rosin soap. Further tests showed that it is hardly possible to use a pure rosin soap for detergent purposes and that mixed rosin soaps were inferior in foaming power. Turkey Red Oil-Soda solutions gave but little foam, which is evanescent ; in hard water a lime soap slime is obtained. Again, mixtures of Turkey red oil soap and fatty acids had no special advantages. Detailed experiments with hard waters showed that in no case did the presence of soda prevent the formation of lime soap. The addition of alkali reduced the foaming in a marked degree, but on the other hand a small amount of soda had a favourable effect on the foaming power and on the lasting quality of the foam. The foaming of a soap solution in hard water increases if it is allowed to stand. The effect of adding vegetable glue (Gum Tragacanth) was investigated, with negative results, neither increased foaming nor permanency resulting. Clay, also, lowers the foaming power and the stability.

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THE 'THEORETICAL PRINCIPLES OF WASHING, CLEANSING OF

DETERGENT ACTION.

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CHAPTER V.

The Theoretical Principles of Washing, Cleansing or Detergent Action.

The problem of the removal of dirt from a textile fibre of fabric involves in its theory and in its practical methods the principles of molecular physics in general, and particularly the nature of actions at surfaces. It touches upon the properties of liquids and of solutions, surface tension, diffusion, viscosity ; upon dialysis, osmosis, electrophoresis, and the Brownian Motion ; on the modes of formation of drops, of emulsions, suspensions, and true solutions ; on the chemistry of saponi- fication ; on coagulation and precipitation ; and, in short, on all that border-land of chemistry and physics which has now become the Science of COLLOIDS. The practical detachment of dirt from a textile material necessitates consideration of the forces, chemical and physical, which are operative; and conversely, those actions which cause the adherence of foreign matters to the textile fibre. Broadly speaking, such foreign matter may be divided by its occurrence into two forms :— (1) Penetrated, (2) Superficial. Spinning oil soaked into the core of a fibre in the first case, and the gelatine film on a sized warp in the second, may be taken as typical. The common view of the scouring process is concentrated almost exclusively on the surface contaminations of the fibre; it will be seen later that the penetrated matters, e.g., oils from the spinning process, acid from the carbonising, etc., are of equal importance and usually more troublesome to remove. There may be mere mechanical entanglement, as, say, a particle of sand in the scales of a wool fibre; and on the other hand there may be complete absorption by, and saturation of, the fibre substance ; as when a chemical reagent, e.g., acid in carbonising, dyestuff or bleaching solution has sufficiently long continued action.

THE DIRTY FABRIC.

Let AB represent the surface of a textile fabric, the particles thereon being respectively kinds of dirt typical of the

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classification in Chap. VII. It is evident that mere solution in water, cold or warm, will detach the sizing matter and the crystalline salt, together with similar substances. The saponi- fiable oil will require alkali, and solution will then follow the soap formation. The mechanical dirt illustrated by the soot particle and the unsaponifiable mineral oil, can only be removed by the intricate processes leading to the formation, mainten- ance, and dispersal of an emulsion. It thus appears that, in general, the scouring process comprises :—

(1) Solution, (2) Emulsification, (3) Saponification, (4) Mechanical Action necessary to the others ; the final result being the transference of the dirt from the fabric to the scouring liquor, this latter being a complex medium carrying dissolved, suspended, or emulsified materials.

Elementary Colloid Theory.

The colloidal is, in fact, the dynamic state of matter, crystalloidal being the static condition. The colloidal possesses energia.’’—Graham. Modern physical generalisations are tending to regard matter as existing in two main forms :—(l1) CRYSTALLOID, (2) COLLOID. (Gr. kolla :—glue.) The old classification into (1) Solid, (2) Liquid, (3) Gaseous, is now supplemented as to solids mainly by the further division as above. It has undoubtedly been the general position, even among authoritative chemical circles, to regard the crystalloid state of a chemical body as typical; modern discovery is tending to show that this view is narrow and restricted. The conceptions of the colloid state of matter date from Graham’s discoveries in 1861-64. On adding hydrochloric acid to a solution of sodium silicate contained in a dialyser—a vessel enclosed by parchment—he observed that the common salt produced, a crystalloid substance, diffused through the membrane into the pure water in the vessel beneath ; the other product, the silicic acid, separated by this means in the jelly- like colloidal condition,.could not diffuse and remained within the membrane. The experiments of Graham upon a limited number of substances and restricted to a few physical properties, have, in the last half-century, been widely extended ; it appears probable that the colloidal condition is an alternative state of matter in general, and a special series of properties is now defined as characteristic of colloid bodies :—

1. LARGE AGGREGATION. Matter in the colloidal condition, when disseminated in a medium, occurs in larger aggregates than the corresponding crystalloidal forms. Those latter may occur as molecules, or by

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dissociation, even as ions; but colloidal matter is usually present as molecular aggregations visible in the ultra-microscope. While the molecular weight for sodium carbonate is 106, and for common salt 58.5, numbers have been given for colloidal silicic acid of 50,000, and for colloidal starch of 25,000, and gelatine 800. I

2. LOW DIFFUSIBILITY. Such colloid matter has much smaller energy of diffusion than the crystalloid types. Graham gives for common salt the figure 2.33, for sugar 7, while the typical colloid substance albumen has 49 for the comparative want of diffusibility. Further illustration is given in the following :—

DIALYSIS TABLE (Graham). Amounts diffused in 24 hours, at 10-15°C., through

parchment :— ~ Common Salt 100 Glycerine 44 Starch Sugar 27 Cane Sugar 21 Gum Arabic 0.4

Two ordinary crystalloidal solutions, not chemically reactive, e.g., salt and sugar, will diffuse until perfect uniformity results, but two colloids are not mutually diffusible in this way. For this reason, the cells of living organisms, plants and animals, are able to retain in the cell substance and within the walls the various nutrient and other substances necessary to their existence and development. This question of colloid permeability is of great textile importance. It is variable with different media ; thus rubber is penetrable by many organic liquids, but practically impervious to water. :

3. DIMINISHED OSMOSIS. In accordance with these lower diffusibilities, colloidal bodies show much lower osmotic pressures ; the osmotic pressure being due to a striving of the particles of the dissolved substance to permeate the whole solution. Pfeffer gives for 1% solution of sugar an osmotic pressure of 51.8 cms., that for a similar gum solution being only 6.9 cms.

4. VARIATIONS IN CHANGE-POINTS. The lowering of the freezing-point and the raising of the boiling-point so characteristic of crystalloidal substances are, in the case of colloidal bodies of lessened importance. Thus the proportionality between the amount dissolved and the lowering of F.P. occurring in crystalline bodies here

K

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fails: a highly concentrated protein solution amounting to 44% caused a lowering of only six-hundredths of a degree. Similarly, concentrated soap solutions boil at practically the same temperature as pure water. A Crystalloid such as Sodium Carbonate behaves as follows :— Temp. C. 100.5 101 101.5 102 103 104 105 P. Cent. Salt 5.2 10.4 15.6 20.8 31.1 41.2 51.2 Also, while a colloidal solution in general suffers de- composition on distillation, crystalloidal solutions are easily capable of separation in this way. 5. THE TYNDALL EFFECT. In certain researches upon the dust of the atmosphere, the late Professor John Tyndall passed a beam of light through an enclosed space in which artificial clouds of fine sulphur particles, I etc., were produced; these particles thus strongly illuminated were then viewed transversely, the smallest development being revealed in this manner. This method, highly elaborated by the employment of perfected optical appliances by Zsigmondy, Siedentopf, and others, into the ultra-microscope, has been applied to the study of coiloidal substances. The limit of

ordinary microscopic sensibility is near 0.25 vu. (where 1 wu. = 0.001 m.m.); but the ultra-microscope reveals particles no greater than 15 v.u., and by solar light

down to 5 (1 = one-millionth m.m.). It has thus been shown that colloidal solutions are two-phase systems, containing suspended particles; particles of less than half-a-millionth of a millimetre can be detected in a suspension of colloidal gold. 6. DE-SOLUTION. In crystalloids, the dissolved matter from fairly concentrated solutions slowly produces the typical crystalline forms. In the case of colloids the process of coming out of solution is termed coagulation, familiar cases being the setting of glue, starch, or strong soap solutions to a jelly. Scientifically, this is termed change from the “ sol ’’ condition to that of “‘ It may be brought about in many ways, of which mere cooling is one of the commonest. But solutions coagulate on heating, the casein of natural milk by the enzyme action of rennet or by acids, soap solutions by “ and many colloidal solu- tions similarly by addition of electrolytes. This change from sol to gel is sometimes reversible, thus a soap jelly becomes a sol again by simple heating ; the colloidal Silicic Acid, however, cannot be retransformed in this way.

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7. ELECTRICAL RELATIONSHIPS. There are signifi- cant electrical phenomena connected with colloidal, as with true solutions. Compared with these latter, colloidal solutions exhibit a diminished conductivity. A more important factor is that of electric charges on the suspended particles. If electrodes are placed in a colloidal medium, it is found that the particles wander in one direction or the other, thus proving that they are electrically charged. Thisis ELECTROPHORESIS or in medical language CATAPHORKSIS. The differ- ence of potential between wool and water is about 0.91 volt, with cotton only about 0.06 volt. Thus most substances, including the textile fibres, wool, cotton and silk show negative charges, as also do china clay, tannic and stearic acids, and the direct, acid, sulphide and vat colouring matters. It is an interesting observation that the negative charge on wool is a maximum of 40°C. If the medium is changed, this electrical charge may vary also; thus wool in an acid solution acquires a positive charge. Basic substances like Iron, Magnesium and Aluminium hydro-oxides take positive charges in water, travelling to the cathode. In general, all solid substances take a positive charge in acid liquids, and a negative charge in an alkaline liquid. It has been stated that soap solutions with cotton exhibit maximum contact electrification at about 1 in 200 of normal strength. These electrical charges on particles in a sol are much smaller than the charges carried by ions in the well-known processes of electrolysis. It is certain that these charges play a part in the phenomena of coagulation and precipitation ; thus crystalloids may precipitate colloids, and two oppositely-charged colloids may mutually coagulate each other, e.g., gum arabic and gelatine in acid solution. 8. BROWNIAN MOTION. Particles below a thousand micro-millimetres exhibit the so-called Brownian Motion, an incessant dance of apparently irregular type, probably due to an unbalanced molecular bom- bardment or some aspect of the kinetics of the particles. It is the more rapid the smaller the particles, and is unceasing even over periods of months or years, and is not influenced by light or heat directly, being in fact independent of external energy. It varies with the dilution, the path-length being inversely proportional to the viscosity of the medium. In the hands of Perrin it has yielded some remarkable measurements of mole- cular magnitudes and atomic constants agreeing in the most striking manner with those resulting from other

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and entirely different lines of research. It must obviously play a part in the mechanical detachment of foreign particles from the surfaces of fabrics submitted to a detergent operation by colloidal solutions.

Suspensions containing particles as large as 10 uw. = 0.01 m.m., exhibit colloidal properties, e.g., the Brownian Motion; for the purposes of classification, such particles are called “ microns.’”’ The lower limit

for the micron may be taken at 0.2 u., and is about the limit of ordinary microscopic visibility. Sub-microns are detected by the ultra-microscope, and range from

0.2 uw. to the lower limit, 3 =0.000003 m.m. The term ‘‘ amicron ”’ is used for particles which cannot be detected in the ultra-microscope. The magnitude of the Brownian Motion is dependent at a given temperature on the viscosity of the medium, and on the diameter of the sol sub-microns, i.e., the Brownian particles; Zsigmondy gave the following figures for colloidal gold :—

DIAMETER IN AMPLITUDE IN MICRO-MILLIMETRES. 0.001 mM.M. 6 10 & upwards 10 3-4 35 1-7

Prof. Jackson placed some cotton fibres in a cell upon the stage of a microscope. On adding pure water, some particles were detached, showing Brownian Motion. In a soap solution this was much increased, but in a 9% common salt solution it ceased entirely, clustering and quiescence resulting. Brownian move- ment slackens in jellies as they become concentrated and 7-10°% solutions are quiescent and homogeneous.

General Summary of Solution Theory and States of Matter.

Modern research is now teriding to bring into line many phenomena hitherto regarded as unrelated, e.g., contact actions—particularly electrifications—at diverse surfaces ; solution in general, i.e., the dissemination of one substance throughout another; the variation of properties with extent of surface, e.g., surface tension, adsorption, etc. ; together with diffusion, capillarity, suspension, ionisation, coagulation, crystallisation, and many others. In particular, the con- ventional notion of a solution as generally a liquid containing disseminated solid must be broadened. This type of solution— in modern language, a double system consisting of a liquid continuous phase having a solid disperse phase—is one only

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?

among many double systems. The concept “ solution ’’ must be held to include all mutual combinations of any of the three broad divisions of matter :—Solid, Liquid, or Gaseous ; that is, of a solid, liquid, or gaseous “‘ disperse ’’ phase disseminated in a solid, liquid, or gaseous “‘continuous”’ phase. The disseminated or dispersed substance is the “solute”’; the medium is the *“‘ solvent.’’ It will still remain, of course, that the liquid continuous phase type will be regarded as standard or normal, being most frequent, particularly in the common case of water as solvent, and especially in the colloid instances. But generality of treatment requires the broader point of view.

There may thus exist systems of the following types :—

DISPERSOIDS. I I I SUSPENSIONS, COLLOID TRUE EMULSIONS, SOLUTIONS, SOLUTIONS, e.g., seak ”’ e.g., starch e.g., brine, syrup, liquors, scours, solutions. etc.

etc. In the broad sense, therefore, we may have solid solutions such as the metallic alloys ; ordinary liquid solutions as of the common salts of the laboratory, and the more uncommon mercury alloys, the amalgams ; solutions of gases in liquids, e.g., ammonia liq. ; of liquids in liquids, e.g., alcohol in water ; and so on. If the particles of a solid or liquid in another medium are distinguishable, say, by the Tyndall effect or other of the properties summarised previously, the class of colloidal solutions is approached ; and at the other limit these shade off into the coarse suspensions or emulsions, according as the dispersed substance is solid or liquid. A typical colloid is gelatine, which shows in both jelly and solution a slight Tyndall effect, though the ultra-microscope reveals no definite particles. The swelling up in water is a characteristic indication of the colloidal condition as contrasted with the dissolution and dispersion of crystalloidal solutes. Gelatine solutions are coagulable by lowering of temperature, and are reversible, and they do not dialyse. Most of the components of the finishes and dressings of the cotton trade are colloidal, e.g., starch, dextrin, the gums, albumen, isinglass, extracts of sea-weeds, etc. The properties of soap solutions are typically colloidal, and the textile fibres themselves, in the normal state, are colloids. Prof. J. W. McBain gives the following table, illustrative of the circle of continuous transition between types of solutions and sols :—

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GROUP. EXAMPLES. ACTIVITY. TIVITY. Crystalloid, non- Sucrose electrolyte : Semi-colloid Dextrines -- Neutral Colloid Pauli’seggalbumen Charged Colloid Gold sol + + Colloidal electrolyte Soap, dyestuffs ++ Crystalloidal . electrolyte Pot. Chloride ttt ++4 Mercury Chloride -+-+-++ + Cryst. non- electrolyte Sucrose >

These considerations point to the necessity of regarding many textile operations—and particularly those dealing with the fibres in the wetted state, viz., scouring, milling, crabbing, dyeing, etc.—as concerned with matter in the colloidal state. Hence, in the application of chemistry to textile operations, the ordinary laboratory point of view, mainly occupied with the alternative crystalloidal side, must be modified. In particular, the immense importance of actions at surfaces of bodies, and the high intensification of such actions when the superficial boundaries of matter are extended by minute subdivision, must be realised. Consider the following illustration. If a cube of one centimetre side (2.54 cms. = 1 inch), is divided into cubes whose sides are one-millionth of a centimetre, the total surface is 60 square metres (1 sq. metre = 1.196 sq. yard), i.e., over 70 square yards. Thus, when a substance undergoes such enormous subdivision as is revealed by the ultra-microscope in colloidal solutions, and its specific surface—i.e., the ratio of surface to volume—is multiplied in the manner shown above, then special interactions occur between substance and medium quite outside the conditions of ordinary chemical or physical working. On the figures of Lobry de Bruyn and Wolff, if a cubic centimetre of dry starch could be subdivided into its molecules or dissolved in the ordinary sense of the word, it would present a total surface of several thousand square metres towards the solvent, and in doing so would pass from an average size of its individual

particles of 20 through the value 0.1 ¥., which represents the

limit of microscopic visibility, to a value of 1 a figure somewhat smaller than that of a particle hitherto observed with an ultra-microscope. Consider again the acceleration in the reaction by the use of Zinc in the form of dust in the Hydrosulphite indigo vat; and the pyrophoric properties acquired by very finely divided metals. Among the mutual actions at the interfaces of substance and medium are

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Adsorption, Surface Tension, Contact Electrification, along with Viscosity, Diffusion, etc.

Surface Tension and Capillarity, It is now almost a fact of popular knowledge that liquids possess at their free surfaces a “ so to speak; a layer having properties different from the general mass of the liquid. The familiar experiment of floating a needle on water, the varied phenomena exhibited by soap bubbles, the clinging together of the hairs of a wet brush, the formation of drops, the ascent of liquids in capillary tubes, etc., are illustrations of this effect. These and similar phenomena point to the existence in the surface layers of liquids of a condition such that the application of external force is required to distort or disrupt the surface film ; and a restoring force is brought into play to keep the form and dimensions of the surface of separa- tion constant. It is as if a contractile force were exerted tending to reduce the surface to a minimum. The thickness of this “physical surface” is of the order 10-50 micro- millimetres. This surface tension has different values for different liquids and for solutions. Every scourer has noticed that cloth pieces running in soap open out as fully as the machine permits; in the washing-off stage they bunch up again into the rope form. This is owing to the fact that the surface tension of pure water is higher than that of soap . Solutions, and the contractile force, acting in every elementary water film in the meshes of the fabric, draws up the piece into a narrow rope, exactly as the bristles of a paint brush bunch up when dipped into water or oil. A table of surface tensions, i.e., Skin-strengths, of liquids entering into textile practice in one way or another, is here appended :— SURFACE TENSIONS. (In dynes per centimetre.)

TENSION TENSION en ee! AGAINST AIR. AGAINST WATER. Water 73-81 (i.e. approx. 34 grains per inch). Carbon Disulphide 32 Mercury 540 418-370 Chloroform 31 29 Alcohol (absol.) 25 a Olive oil 37 21 Turpentine 30 12 Petroleum 32 28-48 Hydrochloric acid 70 — Sulphuric acid 62 — Ether 17.6 — Acetic acid 23 0.7 Benzene 29 35

Carbon Tetrachloride 27 ne

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The wetting-out of a solid immersed in a liquid means that a layer of liquid remains when the bulk is poured away. If T.., and T,, are the surface tensions between solid and air, liquid and air, and solid and liquid respectively, the wetting of the solid involves that ie > Da tr La The liquid will spread over the surface of the solid until there is no direct contact between the solid and the air. The inter- face between solid and air will vanish in favour of the solid- liquid interface, and the liquid-air interface ; the free energy of the former is greater than the sum of the other two. Now the lower the surface tension of a liquid the more easily it spreads upon a surface. Compare, for example, in the light of the numbers in the foregoing table, the behaviour of quick- silver and petroleum when split upon a surface ; the remarkable

Toa

Tuto Fia. 25. Fia. 26.

tendency of the mercury to remain in droplets, and the well- known spreading tendency of the paraffin oil to cover any surface, on to which it can leak, with a continuous film. Hence it is obvious that pure water is by no means in the front rank of liquids as regards “‘ wetting-out ’’ property. Hence, again, the necessity for lowering the surface tension of water in detergent processes by the addition of suitable substances. If olive oil and pure alcohol are separately placed in a vessel, the surface tension at their interface is only 12.2; if aqueous alcohol is: used (density 0.92)—-which would itself have a surface tension against air of 25.5—against olive oil the surface tension is only 6.8. These theoretical considerations have a bearing upon the removal of the olive oil and other similar spinning lubricants in the after-scouring of the finished pieces. Further, it is a common practice to put olive oil upon loom- stains—machine oil, mainly of mineral origin—before sending to the scouring process. There is, of course, a second factor in the presence of free fatty acids in textile olive oils, and their ready saponification by the scouring alkali. Some valuable

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guidance is also afforded by the table on p. 112-3in the choice of reagents for the removal of certain stains in textile fabrics. Now let us consider in this aspect some typically colloidal substances. A solution of soap of strength about 24%, brings down the surface tension of pure water against air to about one-third, or conversely, the wetting-out property is increased approximately three times. A solution of saponin—extract of quillaia or soap bark—showed an air surface tension of 46 as against a soap solution of 1 in 40 strength, 28 units.

SURFACE TENSIONS OF COLLOIDAL SOLUTIONS. (Against air, in dynes per millimetre.) Water 8.25 I Egg Albumen 4.9-5.9 Aqueous Bile 5.08 (9% soln.) Tannic Acid 5.86 (10% soln.) Gum Arabic 7.60 me 6

Tsinglass 19 vs Gelatine 7.27 Agar-agar 7.84

Thus it appears that, as regards mere reduction of surface tension or assisting wetting-out, the addition of these colloids is not of much service in a scour; they may, however, have other effects as “* protective colloids ’’ in stabilising or giving permanency to emulsions already formed. N.B.—It must be noted that the surface of water, as Lord Rayleigh’s experiments show, is always contaminated ; special precautions are necessary to obtain water with a surface tension of the tabular value given above. Some interesting light is thrown upon the use of oils in the preparatory processes :—pulling, teasing, combing, spinning, etc., in the textile trade by a research on lubrication by Messrs. Wells and Southcombe, and described in a paper entitled ‘ The Theory and Practice of Lubrication ; the Germ Process,”’ before the Society of Chemical Industry, February, 1920. By the use of the drop pipette, the interfacial tensions against water of various vegetable, animal, and mineral oils were measured. It was found that these tensions, in the case of animal and vegetable oils, were immensely lower than for the mineral oils ; further, this lowering of interfacial tension was due to the presence of free fatty acids in the former. It was demonstrated :—

1. That capillary effects—which are dependent on wetting- out and surface tension—play a fundamental part in lubrication. 2. That the presence of fatty acids lowers the tension of oils against water.

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3. That a perfectly neutral glyceride, i.e., of vegetable or animal origin, possesses a similar interfacial tension to a mineral oil. (Cf. table below.) 4. That the addition of relatively minute amounts of fatty acid, 1 or 2% or less, reduces the tension of a neutral mineral oil to that of animal or vegetable type.

SURFACE TENSIONS OF VARIOUS OILS. (From Pickering’s Oils and Fats.) Scotch mineral 880/885 39.3 surface tension. American mineral 900/907 39.4

Arctic Sperm 44.0 Stettin Colza 47.6 Castor oil firsts 54.7

The bearing of this upon the lubrication of the textile fibres is immediate and it has a further relation to the scouring process. Pure liquids will not form stable films, and per- manency of film is dependent upon small surface tension. The manufacturers of margarine have long been familiar with the fact that oils or fats containing free fatty acids much more easily emulsify with water than perfectly neutral oils or fats. Thus a coconut oil possessing 1.85% of free lauric acid had a drop number of 73 instead of the usual figure 61. But free fatty acid in very small proportions apparently exerts little effect ; against pure water, and with oils of from 0.05 to 0.5%, the following figures were observed :—

Palm kernel oil 74 Butterfat 71 Cottonseed oil 65 Lard 59 Oleo 66 Arachis oil 66 Coconut oil 61 Soya oil 68

These are drop numbers at 35°C., and correspond to surface tensions of about 20-30. (Clayton. ) It is probable that the subject of surface tension in its detergent aspect may prove in the future a fruitful field of research. Particularly is this likely in the direction of the study of interfacial tension and the wetting-out of surfaces. It must not be thought that the subject is far-fetched and over-theoretical. When pieces are put into scouring machine, instructions having been given to the scourer to run them to a given width, it is very common to find the scourer measuring the piece in ten to fifteen minutes and noting a diminution of, say, 2-3 inches. This effect is almost entirely due to surface tension; the cloth, now well wetted-out, is acted upon in every mesh of its weave by the capillary pulls of the liquid scour, and it therefore contracts ; scourers have been known to regard this as the true felting or milling effect aimed at by the designer in specifying his finished width. It is, of course, a purely false contraction, which would disappear on drying

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the pieces at the tenter; to produce a permanent reduced width, the pieces would require to run much longer. Again, some knowledge of the effects of surface tension would prevent much of the irregular and misguided scouring and misuse of materials characterising many wet finishing routines, and of which some examples are given later. The conception of a liquid “‘ skin ’’ and the idea of a “* skin- strength ”’ special to different liquids is considerably aided by practical experimentation. The books of Prof. C. V. Boys on Soap Bubbles, C. R. Darling and Worthington on Drops and — Films, etc., contain a large number of illustrative experiments of the utmost value from the surface tension point of view. If liquids of equal density are chosen, large drops, balls of 1—2 inches diameter, may be formed which will float immersed in a mass of water, the effect of gravity being thus equilibrated. To secure this, advantage may be taken of the fact that certain organic liquids, immiscible and practically insoluble in water, are equidense with water at certain definite temperatures ; such are Aniline (64°C.), Orthotoluidine (26°C.), ete. If this latter liquid at 26°C. is run from a tapped funnel below the surface of water at the same temperature, large spherical drops even two inches or more in diameter may be formed; every displacement of motion of the liquid makes evident to the eye that the surface of separation is a boundary having special properties, i.e., a kind of elastic bag, as it were, confining the mass of the orthotoluidine. Fine powders dusted on the upper surface of a liquid may be used to reveal changes of surface tension :— 1. If sulphur flour is dusted on the surface of water and the liquid heated at one point by a small jet, the powder moves away; the warm liquid has a smaller surface tension, the colder surrounding area draws the film of powder away. 2. Lycopodium powder may be dusted over a water surface and small drops of various solutions, e.g., soap, sul- phonated oil, solvents, etc., allowed to fall thereon. The retreat of the floating dust shows the reduction surface tension. Again, certain oils contaminate the surface of water, e.g., oleic acid, and excess of such oil forms into drops. If on to these drops small quantities of soap solution, soluble oil, solvents, etc., are placed, their dispersive and disruptive effects in breaking up the film as a preliminary stage in emulsification may be observed.

VARIATION OF THE SURFACE TENSION OF A SOAP FILM

The diagram illustrates a useful lecture-table experiment for showing an effect of lowering the surface-tension of a soap

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film. A bent thistle-funnel is supported with the mouth vertically downwards, and is provided with a rubber tube and clip. An approximately spherical bubble is blown (about six cm. diameter) with a good soap solution. A few drops of a mixture of equal parts of ether and soap solution are run on to the rim of the funnel, and the excess drop is taken off from

pia.

the bottom of the bubble with the pipette. The bubble becomes ellipsoidal in shape, owing to the lowered surface- tension being unable to support the weight of the film as a spherical bubble. That this is not chiefly due to the weight of the liquid added is shown by repeating the experiment with drops of pure soap solution and again removing the excess drop. As the ether evaporates, the film regains its approxi- mately spherical form. When the surface tension of a pure liquid is lowered by addition of some second substance, there follows a special concentration in the surface of this added body. Thus, soap, which lowers the surface tension of water to about one-third the normal value, is present in the surface to a greater extent than in the general mass of the water. Hence a soap froth— an enormously extended surface—is more concentrated in soap than the liquor below. The possibility of forming soap bubbles from soap solutions depends on the lowered surface tension— i.e., the weakening of the liquid skin—and this increased concentration of the soap in the films, which confers a degree of rigidity and stability on them. Dewar has kept soap bubbles in enclosures with a suitably humid atmosphere for many weeks.

INTERFACIAL TENSIONS.

The term surface tension of a liquid applies ordinarily to the surface separating the liquid and the atmosphere, i.e., the upper surface of the liquid, but such liquid-air surfaces exist in the

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bubbles of a froth and there must exist similar properties in the surfaces of separation of two liquids, and also of liquids and solids. These latter are called INTERFACIAL TENSIONS ; they are of extreme importance in scouring operations. It should be well recognised that there are distinctive properties in the surface layer of both solids and liquids. The growth of a crystal in a solution shows that an attraction exists there for atoms of a similar substance, and the facts of absorption illustrate these surface phenomena in a wider way. Lord Rayleigh has shown that freshly-formed and pure water surfaces rapidly become contaminated by greasy matter from the atmosphere. Indeed, it may be considered that in the scientific aspect, the work of the textile scourer consists in the removal of superficial films of various impurities, leaving as the result a continuous fibre-air surface ; or possibly a fibre-water surface. In general, the interfacial tensions at the surface of separation of two liquids are less—and often much less—than the ordinary air-liquid tension. W. C. Reynolds (Trans. Chem. Soc., 1921) measured the interfacial tension between benzine and a soap solution containing 1% of olein saponified by caustic soda; he found it to be equal to 3.5 dyne/em. ; when the solution contained 10% of the soap the interfacial tension dropped to 1.6 dyne/em. The ordinary surface tension of the benzine was 29, that of the first soap solution 26, and of the 10% solution 27. For benzine-water the interfacial tension is about 35, for ether-glycerine 15, water-paraffin oil 48, water-ether 9.7, water-isobutyl alcohol 1.8, etc. No data seem available for the liquids usual in the scouring of textile fabrics or fibres. Reynolds found that in general “ the interfacial tension between two liquids A and B is the difference between the surface tension of A saturated with B, and that of B saturated with A.”’ The table gives the interfacial tensions of a number of liquids against water :—

S. T. OF S. T. OF

SURFACE LIQUID WATER INTERFACIAL

TENSION TENSION ous... 9 OF sons CALCU- OB- DRY LATED. SERVED. rr gtr Bae Benzene 28.4 28.8 63.2 34.4 34.4 Ether (ethyl) te ge i 17.6 281 10.6 10.6 Aniline 41.9 42.2 46.4 4.2 4.8 Chloroform 27.2 26.4 59.8 33.4 33:3 Carb. Tetrachloride 26.7 70.8 43.5 43.5 43.8 Cresylic acid 37.1 34.3 37.8 3.5 3.9 Petrol 22.0 22.0 69.6 47.6 46.4 Paraffin oil 24.8 24.7 73.0 48.3 48.7 ‘Turpentine 27.2 a oa 63.0 35.8 34.2

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The surface tension of benzene is about 28 and that of water about 72 at a temperature of 25°C.; if the liquids are con- sidered as mutually saturated, the values become 28 and 60 respectively. The boundary or interfacial tension is 365. Hence the expression :— 60 — 28 — 35 = — 3 approx. and benzene saturated with water will not spread on water saturated with benzene, but remains in drops. Using the values for the pure liquids :— 72 — 28 — 35 = 9 and the benzene spreads until the surface of the water is reduced by the dissolved or adsorbed benzene. This explains the fact well-known to stain removers and dry cleaners that benzene does not work well on damp surfaces.

WETTING-OUT.

Solid bodies must possess in their external layers a surface tension, though it is not so apparent as in the case of liquids, for the deformations by stretching or contraction are not so striking in solids as those displayed in the formation of bubbles, for example, from a soap solution. Some values have been obtained for certain solids, but there are no general data available. There exist, however, differences in the case of the textile fibres which lead to marked variations in the ease of wetting these materials ; it is well known to all scourers that cotton is more rapidly wetted than wool. Chlorinated wool wets more easily than the normal untreated fibre. When a liquid does not spread over a solid, the surface of the liquid joins the solid at an angle, termed the contact angle ; for complete wetting, such as pure water upon a chemically clean glass surface, the contact angle is plainly zero. On contaminated surfaces or in conditions of mutual insolubility, liquids tend to collect in drops. These conditions of drop formation, or spreading, depend upon the surface tensions of the solid and liquid and the interfacial tension, and the very practical matter of wetting-out rests primarily on the study of surface tension. Thus, when a needle is floated on water it can be made to sink immediately by dropping a trace of soap solution on the surface of the fluid. Generally speaking, the lower the interfacial tension, the greater the ease of wetting-out. Leslie has given a simple physical explanation of the spread- ing of one liquid on another, say, oil on water, as follows :— ** Let it be supposed that the attraction by a molecule of water on a molecule of oil is greater than that called into play between two molecules of oil at the same distance apart. When a drop of oil is placed on the surface of water a layer of oil in the neighbourhood of

the interface, and of a thickness equal to the range of molecular attraction, will be gompressed by the attraction of the water, and

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the oil molecules will be squeezed out laterally. Similarly, if several layers of shot be placed between two flat plates, the shot can be squeezed out sideways by pressing the plates together. The flow above, if not opposed, will continue until a single layer of oil mole- cules alone (Phil, Mag., 1802.) Lord Rayleigh found that certain oils, e.g., olive oil, would spread over the surface of water until a film one molecule thick is formed, when spreading stops. Another mode of regarding the spreading of oil on water and the formation of a film is that the first portion of oil is adsorbed by the water ; any excess not so adsorbed draws up into drops on the oiled surface. If in great excess, a layer of free oil is formed over the whole surface. Plainly, in producing efficient scouring media, it is desirable to obtain the maximum of adsorption effect, an end secured by the formation of lathers on the one hand, and by fine-grained emulsions carrying dispersed grease coated with soap films on the otherhand.

Some interesting effects are observed when mixtures of liquids are employed. Thus, if finely-divided carbon, e.g., lampblack, is placed in water and paraffin oil added, the mixture being thoroughly shaken, the powder is found, partly in paraffin, and partly in the interface. With carbon tetra- chloride, benzene, or ether, it goes entirely into these liquids, deserting the water phase and also the interface. This phenomenon of preferential wetting is quite general and has a distinct bearing upon scouring practice. It would bea suitable practical problem for a research laboratory to take the textile fibres and the most frequent forms of textile ‘“‘ dirt’’ (See Chapter VII in Practical Scouring) and determine the wetting conditions for the usual alkaline scour with additions of ** solvents,”’ ete.

It appears that the wetting power of a liquid depends also upon the property of certain substances to bring about a condition of surface concentration (or capillary adsorption), a state closely connected with the power of foaming or frothing ; it would seem that in such cases there is a marked superficial viscosity or rigidity. For example, a 1% solution of saponin will wet a glass plate coated with paraffin, while a 5% solution of soap fails to do so. But it is evident that if a liquid is to possess wetting-out power in a high degree it must have a low surface tension and also a low boundary, i.e., interfacial tension, to the object to be wetted. It need not, therefore, follow that scours working well on certain fibres or solids should prove equally efficient on others, and this is in accordance with’ practical experience.

By far the commonest kind of surface in textile working is

the greasy type, but there are also special cases, e.g., the gum coating (sericin) of the silk fibre, mineral soaps in slipe wools,

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loose dyestuffs, etc, For these, other forms of treatment, to the usual alkali-soap scour—fuller’s earth, quillaia, boiling lathers, etc.—may be preferable. An instructive table of experiments by W. H. Nuttall, illustrating the attack of soap on a mineral oil (Castor oil soap on liquid vaseline) at various concentrations of the soap solution, is appended :—

CONCENTRA- SURFACE SURFACE TION OF TENSION OF TENSION INTER- WETTING- FATTY SOAP OF FACIAL OUT ACID. SOLUTION. VASELINE. TENSION. POWER. 3 Oo T 1 T 2 T 13 0.0001 70.76 Dike 129.28 —98.17 0.001 56.61 108.43 —77 .32 0.01 33.45 oa kk 76.46 —45 .32 0.3 33.45 Silt 27.39 —20.73 0.5 wes 11.98 —14.32 1.0 33.45 an kk 10.93 —13.27 2.0 33.45 8.23 —10.57

It is evident that while from a concentration of 0.01 upwards of fatty acid in the soap there is no variation in the surface tension of the solution, the boundary tension of the soap-vaseline surface diminishes progressively. It is probable that at about the value 0.1, a marked attack—disruption and emulsification— on the mineral oil would be shown. The soap solution acts as an emulsifier because of the low interfacial tension. The familiar increase of wetting-out power due to heat follows directly from the law of diminution of surface tension with temperature. In the case of water :— Temp. C. 18 36. 68 89 Surface Tension 76.7. 73.6 T.0. G68 60.9 At 100°C., when the water becomes steam, i.e., the liquid turns into the vapour phase, the surface tension vanishes ; it vanishes also in the case of perfectly miscible liquids like alcohol and water. The immediate practical conclusion from this is, that other things being equal, warm scouring is to be preferred.

FORMATION OF FOAMS, FROTHS, OR LATHERS.

The question of Lathering, Foaming, or Frothing, in detergent liquids, naturally arises from the theory of surface tension. It is characteristic of colloidal solutions to form froths, foams, or lathers by agitation, an effect which has given rise to the popular but erroneous notion that an emulsion is necessarily a mixture showing abundant frothing. Scientifically speaking, an emulsion is a disperse system, both phases of which at ordinary temperatures and in bulk are liquids. It need show no foam whatever. The property of frothing depends upon the lowering of the air-solution tension ;_ this is directly connected with the wetting-out stage of the cleansing process. The bringing of dirt from the fabric into the medium

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depends upon lowering the interfacial tension of the dirt— which is generally oil or grease—and the soap solution. This lowering of the dirt-soap solution tension as a detergent factor generally accompanies the lathering property, but not necessarily so; good detergents may, and indeed do exist, which have little foaming-power. Consider the two following illustrative cases :— In Case I, a drop of oil spreads when placed upon a water surface, but in Case II, the drop of water does not spread upon the surface of oil. Let the several tensions be (1) T,,,, tension between oil and water; (2) T,,, tension between water and air; and (3) T,,, tension between air and oil. Now the results of experiment show that the water-air tension is greater

28,

than the combined tensions of the oil-air and water-oil surfaces. a, wag + Frags Thus for olive-oil and water the inequality is 80 > 37 + 21. See table of surface tensions in Chap. V.. Hence the tendency of the water-air surface to contract is greater than the opposing contracting tendencies of the oil-air and water-oil surfaces together, and the water therefore remains in the form of a drop. In the first case, the contractile tendency of the oil-air surface represented by 37 units is less, and considerably less,

L

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than the sum of the contracting tendencies of the interfaces water-air and water-oil, 80 and 21 respectively; the oil, therefore, immediately and readily spreads as a tenuous film over the water. Returning to the “ lathering ”’ problem, it will now be seen that the foaming is a matter of surface activity in the particular case of air only, whereas the general detergent requirements imply surface activity against other substances also, among these being the solid or liquid ** dirts,”’ particularly the textile oils or greases. This second aspect needs something further, viz., the lowering of the water-grease tension with consequent wetting-out, loosening, and emulsification. But in general the capacity to lower the air-water tension goes along with capacity to lower the grease-water tension, e.g., soaps dissolved in the water. It is not therefore ordinarily a false deduction to regard foaming-power as good scouring property. Again, the mere mechanical formation and bursting of the bubbles of a froth is undoubtedly a factor in displacing dirt particles or grease droplets from a surface; just as the steam bubbles forming on the surface of a dissolving solid on boiling assist its solution in the liquid. There is another factor connected with the excessive extension of surface or multiplication of interfaces involved in the formation of foams or lathers. Prof. Gibbs has shown from the theory of thermodynamics that—at any rate in a reversible process—if the addition of a solute lowers the surface tension of a solvent, the solute will tend to concentrate in the surface layers ; and vice versa. Sisley has given experimental evidence of concentration in a foam; safranin solution, 0.02 gm. per litre and 2 c.c. of glacial acetic acid were shaken up with chloroform; the colour collected in the emulsified chloroform, the aqueous layer being decolorised. He further states that Tri- or Tetra- Nitro diphenylamines do not dye silk from aqueous solution, but will do so from a “ broken soap ” bath. Soap dissolved in water lowers the surface tension to approximately one-third the value, and hence there results a concentration of soap in the surface ; in other words, a soap lather contains relatively more soap than the body of the solution. This has been verified in experiments by Donnan, Lewis, and others. This surface concentration is a direct cause of permanency in a lather. Mere air-froths are well known to be quite evanescent, and they have, of course, no detergent properties.. There is also the special efficacy of foams in causing thorough wetting-out. This is practically applied in the technical process known as ‘** Foam Dyeing,’ used mainly for cops and cheeses on cotton with direct or sulphide dyestuffs. The goods are held in a cage clear of the liquor, to which soap or other frothing agent

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has been added ; only 3.or 4 times the volume of liquor is required. The action of wetting-out, even on dry material, by the froth is practically immediate, but the process is in- applicable where perfect evenness of shade is desired. Another example of facilitating wetting-out by the differences of surface tension is the modern Flotation Process for separating ore particles from the gangue minerals, and also the Elmore Processes for mineral separations. It would thus appear that a foam, froth, or lather has valuable properties in detergent operations, evidently pro- moting rapid wetting-out of the material, and being particularly effective where capillary penetration is necessary. When, therefore, the “shaving soap” illustration is employed to prove that foaming is futile as a factor in cleansing, it is probable that there is over-statement. The high lathering properties of a shaving-soap—sometimes intensified by added colloid, such as gum tragacanth, etc.—are required more for softening and anti-drying utility than for saponification of fatty acid or emulsification of grease. For this softening effect, i.e., ready wetting and penetration, free foaming is desirable. It is desirable also in textile scouring, but, as the mathematicians would say, it is not in itself a necessary or sufficient condition. Further, liquid foams may be produced by bodies other than soap, e.g., albumen water; and notably through the use of soap-bark in the washing off of indigo blues by fuller’s earth and its extracts by dyers. Finally, therefore, it may be concluded that the property of foaming or lathering is one of the factors in detergent practice ; other things being equal, it is desirable that.a detergent material should secure this forma- tion in general. The addition of colloids such as gelatine, various gums, etc., to a soap may be favourable ; electrolytes, whether derived from hard waters, or in the form of excess of alkali or added salts, are prejudicial ; moderate increase of temperature, say, to blood heat, is useful ; and the mechanical action of the scouring machine, with the consequent entanglement of air in the capillary channels, is necessary. The foaming of pure liquids is a temporary affair, because in this case the surface tension is constant at all extensions ; if however, there is a Gibbsian concentration in the surface layers in composite liquids, i.e., in solutions, then there is a variation in this surface tension, with extension -and permanence of films. The power of foaming, like emulsifying, is not always or entirely due to low surface tension ; for instance, saponin solutions whose surface tensions are only slightly less than that of water, have a very great power of foaming, on account of the formation of a solid or highly viscous film of adsorbed material in the surface.

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Diffusion. Graham :— all the properties of liquid colloids, their slow rate of diffusion in

water and their inability to pass or penetrate a colloidal septum are: the most useful in distinguishing them from crystalloids.”’

Parrot, 1815 :—

‘** All miscible liquids show a tendency to wander one into the other when they are brought into contact, and this process continues until they are perfectly equally distributed.”’ Another physical process which is operative in technical scouring is that of ordinary liquid diffusion. Diffusion is most marked in gases, though a characteristic property of fluids in general; the introduction of a second gas into any space already occupied by a gas is followed in a short time by the thorough permeation of the space resulting—chemical actions being neglected—in a uniform mixture of the two gases. A similar process occurs with two or more liquids mutually chemically inert, being complicated, however, by differences of density ; the process also being much very slower in liquid than in gaseous media. A layer of water placed over a salt- solution in time becomes intermingled, and a homogeneous salt solution of lower concentration results. Graham carried out many experiments on the diffusion of liquids. He showed that acids diffused about twice as quickly as neutral salts; that caustic alkalies are less diffusible than acids ; that diffusion is proportional to the concentration and varies with the temperature. It was found that a solution of common salt at 4.2°C. gave 10 gms. in the diffusate in eight days, but at 19.4°C., 13.6 gms. of salt had diffused. As regards the presence of other salts, Graham found that 9.06 gms. — Sodium Carbonate diffused in eight days from a 4% solution into pure water; and into a 4% common salt solution 8.82 and 9.1 gms. respectively for two experiments. Some com- parative results by Scheffer are here appended; “N” = number of molecules of water for one molecule of substance :—

DIFFUSION SUBSTANCE. TEMPERATURE. N. COEFFICIENT. Hydrochloric Acid 11° Cent. 2.67 I I 11 108 .4 1.84 Nitric Acid 9 35 1.78 a 426 1:73 Sulphuric Acid Li 8 18.5 1.07 Caustic Potash 13.6 166.5 1.66 Ammonium Hydrate 4.5 16 1.06

It must be remembered that the diffusing liquids are in the mass absolutely steady and quiescent ; the diffusion represents the intermingling caused by molecular or ionic activity. In textile practice, all dyeing and cleansing operations involye

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agitation, often very violent, by mechanical or other means. It follows, therefore, that any effects of diffusion proper must be completely outweighed by the mixing due to stirring, pumping, steaming, or mechanical agencies generally ; but steeping and fabrics standing in the wetted state involve this property. The diffusion of liquids is dependent also on their VISCOSITY, in common language, their stickiness or sluggish- ness ; a table of viscosities is here given :—

TEMPERA- COEFFICIENT SUBSTANCE. TURE. OF VISCOSITY. Water a eae, 0.0178 20 .0102 80 7 Water with 7 Glycerine 94% 8.5 7.444 80%, 1.022 64% 0.222 50% 0.093 Glycerine puriss. 2.8 42.180 26.5 4.944 Alcohol 0.0154

The enormous reduction with rise of temperature is apparent. Obviously liquids increase their mobility, and hence their penetrating powers, with heating ; on this ground, therefore, the theoretical contention that a warm scour is preferable to cold scouring, is borne out. Viscosity is a useful property in emulsions, tending to their stabilisation and permanence. The related problem of permeation of a solid from a liquid— both quiescent in mass—has not received equal attention. Graham found that the rate of diffusion of substances into dilute starch, gum, etc., was practically the same as into water. I And Voigtliander, experimenting with a cylinder of agar-agar jelly, confirmed this. Using a 0.72% solution of sulphuric acid, the following amounts in milligrams were obtained in 0.5, 1.0, 2.0 and 4 hours respectively ; 0.74, 1.08, 1.48 and 2.16 mgms. ; In strong solutions or gels, diffusion is diminished. The general action of membranes immersed in liquids is still a subject of controversy. There may be mere sieve-like action, or adsorption with or without chemical actions ; or possibly a pseudo-filtering action due to capillarity. ;

Adsorption.

Absorption: To swallow up; to engulf; to imbibe; to cause to disappear, as if by swallowing up; to take up by cohesion, chemical or any molecular action. Adsorption : To suckin. A common phenomenon consisting in the adhesion of the molecules of gases or dissolved substances

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to the surfaces of solid bodies resulting in a relatively high concentration of the gas or solution at the place of contact. (This may also occur with two immiscible liquids in contact, the one containing a material in solution, which is drawn from it by the other, in which it is also soluble, until it becomes relatively more concentrated in the second liquid, chemical action, of course, being out of question.) Absorption therefore means taking up the liquid as a whole just as a sponge takes up water. Adsorption means the concentration of some constituent of the liquid either on a solid surface or in a_ second liquid phase. (Webster’s Dictionary.) If dilute solutions of colour, e.g., methyl violet or methyl green, in strengths of 0.002°% are shaken with a few grams. of fuller’s earth, blood or bone charcoal, kaolin, etc., they become decolourised. Even chemical salts may be extracted from solution in this way, e.g., Lead Nitrate, 2 or 3 drops per 100 c.c. the solution after agitation with charcoal shows little or no reaction with Ammonium Sulphide. Many salt colours are soluble in alcohol and indigo is soluble in chloroform, and many sulphide dyes are soluble in sodium thiosulphate or more frequently in sodium sulphite; yet when dyed, these colours cannot be completely stripped by the reapplication of these solvents, or at any rate only by very prolonged treatment. Dreaper states that an aqueous solution of Night Blue, when passed through sand, dyes the sand, and a certain amount of the solution comes away devoid of colour. Thus from a 0. solution of the dye, the silica absorbed 2.2 c.c. before the liquid passed ; then 6 c.c. passed colourless. Similar results were obtained in other cases. Again, it is known that gases form dense films, difficult to remove, on the surfaces of glass vessels, such as X-ray bulbs; a phenomenon requiring special pre- caution when attempts are made to produce high vacua. Charcoal exhibits the property under discussion in a high degree both in condensing gases upon its surface, and in extracting matters from solutions, being extensively employed in labora- tory experiments and technical processes for this purpose. It thus appears that certain solids, immersed in solutions, may extract dissolved substances therefrom in a concentrated or condensed form upon their surfaces ; this property is known as ADSORPTION. It connotes more than the mere permea- tion of the pores of a body by a solution, i.e., absorption in ordinary language, as in the wetting-out of a sponge. There is a distinct formation of surface layers which contain in a relatively high degree of concentration substances derived from the body of the solution. Diffusion, osmosis, surface tension, contact electrification, and cohesion may, and probably do, all enter into the mechanism of this process ; and possibly

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in some cases at least, chemical action. But in general, both surface and adsorbed substance preserve their chemical identity ; for example, acid groups are still capable of forming metallic salts, and in dyestuffs basic groups can be diazotised or saturated with tannin (Mueller). Adsorption is affected by several factors. If on to the charcoal which has adsorbed a solution of methyl violet is poured alcohol or acetone, some colour is detached; thus the solvent affects the amount of adsorption. It is also influenced by the contact electric charges of different solids immersed or suspended in solutions. Thus sand, which is negatively charged in water, is capable of adsorbing by neutralization positively charged ferric hydroxide from solution ; the same explanation accounts for the retention of Night Blue,a positively charged colloid in aqueous dispersion. Strips of filter-paper—negatively charged in water—act in an analogous manner. When dipped in sols, if these are negative, e.g., Prussian Blue, the colour rises in the strip; if positive, only water rises, separation taking place at the level of the liquid. This has been developed by Goppelsroeder and others into a method of Capillary Analysis. It is possible that some of these are pseudo-adsorptions ; they may really be electrical. This process of adsorption of a substance from solution by an immersed surface is capable of quantitative estimation ; for example, the adsorption of Oxalic Acid by charcoal may be accurately followed by titration with Potassium Permanganate standard solution. As is to be expected, adsorption is a process which proceeds at a diminishing rate. Ultimately a balance is set up when a certain amount of dissolved matter y = k x! has been removed from the solution. Let be the con- centration of the external solution. Then the law of adsorption is y = k x1", where “.k’’ and“ p”’ are constants. This law has as yet no theoretical derivation, being simply a general relation for a diminishing reaction, the curve corresponding to it being of a generally parabolic type. The law has received abundant experimental confirmation by many observers on different substances; and particularly from the desire to formulate a theory of dyeing. (See P. E. King, General Review and Bibliography of Dyeing: Report on Colloid Chemistry, 1917.) It is evident that the mechanism of adsorption must enter into the processes of mordanting the textile fibres and the fixation of dyestuffs thereon ; and it is equally evident that the detergent operations must involve I adsorption effects. Much of the textile “ dirt’? which it is the object of scouring to remove, is fixed upon the fibre by adsorption ; and the treatment with reagents in scouring, the formation, maintenance, and dispersal of emulsions imply adsorption reactions in all stages. Special discussion in another section is given to the retention by the fibre of certain

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materials, e.g., soap, etc., but it is important to emphasise this matter while the subject of adsorption is under discussion. In carbonising, for example, by the use of sulphuric acid, the after-neutralisation by soda-ash must be carefully and thoroughly carried out, otherwise a superficial neutralisation — only is achieved, and the strongly adsorbed residual acid may affect subsequent operations It is not uncommon for car- bonised pieces to ‘‘ crack ’’ the soap emulsions of the scourer or miller, and precipitate fatty acids upon the fabric. It should be remembered that the carbonising acid has the advantage of first application to the newly-scoured wool, and also'a period in the drying or heating stage during which further penetration and adsorption may ensue. Hence the stage of neutralisation should be well controlled. It is possible to secure a pseudo neutrality, where, if the dried-off wool were soaked for several hours or boiled up for a few minutes, the ordinary chemical indicators would reveal liberation of acid, which, having been firmly adsorbed, had resisted an imperfect neutralising operation. Zawidski, in 1900, by adding saponin to solutions of salts with acetic acid and analysing the foam carried over by bubbles: of air, demonstrated the effect predicted by Gibbs ; and Miss Benson, in 1903, working with aqueous amyl alcohol, which foams without external aid, found that the surface concentra- tion in the foam was 0.0375 n. against 0.0304 n. in the original. It is possible, on certain theoretical considerations, to calculate the thickness of the adsorbing layer; in the case of water, it is found that 1 gramme of water can cover 16 x 10° sq. ems., and the thickness of the layer is 0.6 « 107° cm. At this limit, the properties of the substance are different from those of the substance in bulk. The mechanism of the actions in adsorption films is still a subject of investigation. Faraday’s view was that a greater molecular condensation was produced; speaking of the

occlusion of gases by platinum, he says : *“ Hence it would seem to result that the particles of Hydrogen or any other gas or vapour which are next to the platina, etc., must be in such contact with it as if they were in the liquid state, and therefore almost infinitely closer to it than they are to each other, even though the metal be supposed to exert no attractive influence over them.”

And Prof. J. J. Thomson has shown mathematically from Laplace’s theory of capillarity that at the boundary of two liquids capillarity will increase the chemical action. In some experiments upon surface tension he showed that Pot. Per- manganate solutions, deeply coloured, emerged almost colourless after trickling through finely divided silica; a piece of filter- paper dipped in such a solution is almost colourless above a certain height of the wetted area. On the other hand, a small quantity of paraffin oil mixed with water increases in strength

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by such permeation, as the surface tension of such a solution against a solid is greater than that of water. Thus in very thin films the influence of capillarity might be sufficient to modify completely the nature of chemical equilibrium, though we should not. expect it to do much in ‘the body of the liquid . . . . Thus the chemical action in a space such as a thin film throughout which the forces producing capillary phenomena are active might be very different from the chemical action in the same substance in bulk, when most of it would be free from the action of such forces. (Application of Dynamics to Physics and Chemistry). The adsorption layer appears to exert functions analogous to a solvent. Attempts to estimate the thickness of such adsorptive layers have been most successful in the case of gases, there being only a general accordance in other cases, e.g., soap films. Thus, taking the micro-millimetre as the one-millionth of a millimetre, we have :—

MEASUREMENT. RANGE IN Uy, OBSERVER. Thickness of black soap films 12 “Rucker & Reinold. Thickness of normal soap films ‘50 Quincke. Thickness of normal soap films 96-45 Rucker & Reinold. Superior film thick- ness (soap) 118 Plateau & Maxwell.

Some extremely interesting and far-reaching considerations have been put forward in a series of papers to the American Chemical Society, in 1916, 1917 and 1918, by Langmuir, who has shown that it is very probable that the adsorbed layer has its molecules definitely oriented. In the case of thin films of fatty acid floating on water, he states that the carboxyl groups are immersed in the water, while the hydrocarbon chains are in the gas space above :—

Csr.

2

I ee I I COOH COOH Liquid

Langmuir asserts that in considering “‘ the adsorption of a liquid by a plane solid surface, if the molecules of the liquid contain active goups, the molecules will become orientated and will pack into the surface layer in much the same manner as in the case of oil films spreading on the surface of

2

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there is some experimental evidence that a hydrocarbon lies more or less evenly distributed on the surface of water, while with a fatty acid the carboxylic groups are selectively attracted to the water side of the acid film. This attraction is present in a less marked degree between an ester group and water, or between an ethylene group and water. According to this, the adsorbed film should be only one molecule thick, and he differentiates the processes of solution and common absorption from true adsorption in this way. He confirms the work of other experimenters in showing that the adsorptive process is selective or preferential. The whole phenomena are intimately related to the existence at the boundary surfaces of adsorptive bodies of the electrical ‘* double layer ’’ of Helmholtz. Langmuir regards surface tension (or rather surface energy) as principally dependent on the structure of the surface layer of atoms of a liquid. ~** According to this theory, the group molecules of organic liquids arrange themselves in the surface layer in such a way that their active portions are drawn upwards, leaving the least active portions of the molecules to form the surface layer. The spreading of an oil upon water is thus due to the presence of an active group which has a marked affinity (secondary valence) for water.’ It is a striking experimental fact that while oleic acid spreads almost. instantaneously on water—with a speed of 25 to 50 miles an hour, according to Edser—pure hydrocarbons do not so spread or form films. The common mineral oils are often sufficiently impure to show spreading. Following out the general standpoint of his hypothesis, Langmuir states that “the formation of froth depends upon the presence of substances which can form a stable monomolecular film over the surface of each

NOTE ON THE HELMHOLTZ DOUBLE LAYER.

At the interface separating two bodies there exists an electrical double layer. The immersion of solids, for example, in water is accompanied by the development of electric charges the water layer adjoining, becoming oppositely charged. Bodies of the class of electrolytes dissolved in the water may reverse the surface charge of an immersed solid. These phenomena have an influence upon the permanence of emulsions. The effect of alkali in a detergent liquid is to intensify the negative charge on the oil and dirt particles of the immersed surface, at any rate, within small limits of concentration. Acids act oppositely. According to Smoluc- howski, if two particles in Brownian motion are brought near enough together, the double layer is broken, and coagulation ensues. I cet UG

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~The internal physics of solutions and emulsions is con- tinually receiving further investigation, and the phenomena of contact electricity may prove of great importance in supplying a working theory. In the apparatus shown in the accompany- ing figure, the glass tube is packed with cotton, wool, etc., and filled with water; one end is then placed in water. The electrodes are connected to some potential difference, the immersed end being positive. It is found that water moves from the vessel through the tube and drops from the open end of the tube, the reason being that the fibre has acquired a negative contact charge against the water, the p.d. being about 0.91 volt in the wool case. The water being positive moves towards the negative pole. The converse experiment of forcing the water by hydrostatic pressure through the tube results in the development of a potential difference at the electrodes. In a suspension, say of powdered glass or kaolin, placed under the microscope, between electrodes, the trans- ference of the negatively charged particles can be demonstrated. On these facts an electrical theory of dyeing has been based.

Thos Se eS ee FS Pe hey hil) ss a oe le Gos ae

SE

Fic. 29.

Some information on the Wetting of Cotton by the Research Board (Jour. Text. Inst., July, 1925) by Farrow and Neale illustrates the theory. It is pointed out that when one liquid meets another it may be aggregated into globules or spread out into thin or even attenuated films ; in the former case, the contact angle is large, in the latter small. If the following symbolism is adopted :— Tsja is the surface tension between the surface and the atmosphere, Tia that between the wetting liquid and air,

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Tijs the surface tension between the surface and the liquid ; then it is possible to derive an expression termed the Spreading Co-efficient = Ts/a = (Tia + Tis). If the wetting is spontaneous, this has a positive value ; if the wetting is imperfect (reversible) or there is no wetting, it is negative. The table below exemplifies these conclusions :—

E Vv contact: I SPREADING|BEHAVIOUR SYSTEM Ts/a Ts I co- LIQUID

ANGLE. OR OIL. Water (1), Castor Oil (s) and Air 28.9 I 20.7 I 60.3 83° —51.8 (No spread

O.1 Soda Oleate Castor Oil, Air 28.9 I 16.4 I 22.6 56.5 —10.1 No spread Water (1), I Cotton wax(s)} 27 I 14.0°; 42.6 was —29.6 — Air I 0.5 SodaOleate, Castor Oil, Air 28.9.1 +0.4 Spreads

The apparent volume of immersed and dry yarn was taken in water at 88°C.

MULL

TI AAP

Fie. 34. COTTON VISUAL DIAMETER. VISUAL SPECIFIC IMMERSED SPECIFIC (i.e., PROJECTION) VOLUME. VOLUME. Egyptian .O175 1.48 2.5 American .O182 1.74 2.1

The visual specific volume, obtained by an optical projection method, does not take into account the internal porosity, but the immersion hydrometer arrangement gives, of course, the true volume. From 88 to 98°C. the wetting is more complete, and at the latter temperature most of the air is removed, probably all at the boiling point. When a substance of high surface activity is added to water (see table) there is a fall in the contact angle.

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SoAP SOLUTIONS;

THEIR CONSTITUTION AND DETERGENT ACTION.

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CHAPTER VI.

Soap Solutions ; Their Constitution and Detergent Action.

What is a Soap Solution? How does it cleanse? How may soaps be compared in their detergent powers ? These are questions which are, broadly, in the region of inquiry, and in some aspects have received only the most casual attention. In this book a good deal of treatment has already been given to the nature of soap solutions, from the colloid standpoint, and to their mode of operation. (See Chapter V on Theoretical Principles of Detergent Action), Some additional points have come forward in the chapters on Water, on Oils and Fats, and on Soaps. It is now intended - to discuss the special action of soaps as cleansing agents, apart from mere solvent action, such as that of benzine, or mechanical friction, such as the use of fuller’s earth.

SOLUBILITY OF SOAPS.

Soaps differ considerably in their solubility ; primarily this is a question of the alkali, and secondarily of the nature of the fatty acid. Ammonia soaps are the most soluble, the potash or soft soaps next, and soda soaps the least so, of the soaps proper. The more basic soaps of the alkaline earths— magnesium, iron, aluminium, etc.—are insoluble in water. (See Chapter IX on Water-proofing). A 5% solution of ordinary soap gelatinises at the average temperature, whereas a 20°% soft soap solution will still pour, Dr. Clark’s soap-foam test for the hardness of water makes use of Potassium Oleate, the most soluble of the ordinary soaps. The solubility of a soap varies also with the Titre or melting-point of its fatty acids, an exception being cotton oil. Soaps with high per- centages of hardened oils are deficient in solubility. The position of the higher-titre tallows in this respect has already been noticed. Castor-oil soaps, with 30° fat content, have the property of remaining liquid when highly concentrated. While Potassium Oleate is soluble to the extent of one part in four, Sodium Oleate requires ten parts of water.

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It has been shown by Krafft and other investigators that the detergent power of soap is dependent on the particular fatty acid or acids contained ; oleic and stearic soaps exhibit differences in working. Soaps from palmitin and stearin are unworkable at ordinary temperatures, developing their detergent properties at temperatures approximately equal to their melting-points. On the other hand, olein soaps are soluble and exert detergent action at low temperatures, losing this power, however, at about 80°C. Donnan has shown that in ascending the Acetic Acid series of fatty acids, the surface tensions against alkaline solutions become progressively lower. Thus it will be seen that soaps made from pure tallow or high-titre hardened fats exert very slight emulsive powers at ordinary temperatures.. It would be interesting to have a surface tension-temperature curve for, say, Sodium Oleate. Experiments by Shukoff and Schestakoff (Siefensieder Ztg., 1911, p. 982) support these considerations. The so-called Marseilles soap—olive oil and soda compound—dissolved in one quarter of the time of a 20% rosin-tallow soap; and this latter again four times faster than a pure tallow soap. This is the technical reason for the very general addition of coconut or palm kernel oil to the tallow base of fine white curd soaps ; a tallow coconut oil soap, with one-fourth of its weight of the latter component, dissolved nine times faster than the all-tallow soap. It has been stated that in artificial dirt trials, the scouring liquor from tallow and cotton oil soaps held graphite in suspension for several days ; with a castor oil soap it was extensively deposited in afew minutes. In milling, high-titre non-lathering soaps show a tendency to remain in the goods ; free-lathering lower-titre soaps wash out easily.

HYDROLYSIS OF SOAP SOLUTIONS.

Soaps dissolve much more freely at higher temperatures ; their hot solutions are clear, but in the cold they are usually. turbid. This is due to a decomposition of the soap, forming free alkali and leaving an acid soap. Like most dissociations, this increases with the dilution. It depends on the nature of the fatty acids, less hydrolysis taking place in the oleic soaps. McBain and Martin’s results (Jour. Chem. Soc., 1914, p. 967) show that in concentrated solutions, this hydrolysis amounts to only a fraction of 1% ; evenina0.01/N Sodium or Potassium Palmitate it only reaches about 6.6%. This aqueous de- composition or hydrolysis of soap is inhibited by certain agents, such as caustic alkali and glycerine. Alcohol is added to the Clark standard soap solution for hardness testing with the same end in view. In alcohol, soaps are true electrolytes of a non-colloidal type.

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It was a facile but erroneous deduction to ascribe the I detergent power of soaps to the hydrolysis alkali acting by emulsifying the grease of the fabric and saponification of the fatty acid.. But soap solutions will emulsify mineral oil on which alkali has no effect ; and dilute alkali alone is an efficient emulsifier of oils containing free fatty acid. The theory of hydrolysis alkali as the source of detergent function in soaps is utterly inadequate. Jackson, lecturing on ‘‘ Laundry Detergents,’ to the Society of Arts, in 1907, states that soap hydrolysis yields about 2} grains of caustic soda per gallon in the solutions obtaining in ordinary practice ; and also that one part of caustic soda, or equivalent of other alkali, will hold about forty parts of the average kinds of grease or oil met with in a state of emulsion, even when the concentration of the

alkali is not more than 0.05%. PERCENTAGE OF TOTAL ALKALI SET FREE

SOAP. BY ADDITION OF MOLECULES OF WATER TO ONE MOLECULE OF

ANHYDROUS SOAP.

X=150 X=500, X=2000 X=5000

Sod. Stearate 0.7 2.6 3.50 Sod. Palmitate 1.45 2.6 3.15 Sod. Oleate 1.85 3.8 5.2 6.65 Cottonseed oil 3 soap 2.25 5.0 7.5 oo

It is evident that the hydrolysis alkali is a quantity of a comparatively minor order of magnitude.

THE STALAGMOMETER, THEe Drop PIPETTE. Fig. 31. A difficult obstacle in the hydrolysis alkali theory of detergent power is the fact that while hydrolysis is a maximum at low temperatures, detergent action is increased in hotter solutions. Hillyer, experimenting in 1903 (Jour. Amer. Chem.

M

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Soc., p. 1256) on the surface tension of soap solutions against kerosene, showed that the properties of wetting-out dirt and emulsifying grease are inherent in a soap solution and are absent in solutions of alkali alone. The low alkalinity thus evidenced in the hydrolysis of soaps points to the conclusion that their detergent power is not chemical, but physical. Merklen’s view was that :— Soap should not be looked upon as a compound of sodium salts of fatty acids with which a definite amount of water is combined chemically; but rather as an “ adsorption the composition of which is a function of the - environment in which these sodium-fatty acid salts happen to be at the moment of the finishing operation. Finished soap behaves as a colloid; the absorption of water by the colloid soap is a function of :— 1. The structure of the colloid. 2. The nature of the solvent. 3. The nature of the salts and the alkali. 4. The temperature. It would appear that soap solutions constitute an inter- mediate case of a pseudo-colloid nature. They are good electrolytes, but the ionisation thus indicated is not supported by the boiling-point, vapour pressure, and other osmotic properties which differ but slightly from pure water. Parker and Moore’s work on the osmotic pressures of soap solutions led them to the conclusion that soap is not dissolved in water as single molecules, but as “solution (Amer. Jour. Physiol., 1902, pp. 7, 262.) 7 Both dilute and strong solutions possess electric conductivity, indicating hydrolysis or ionisation, or both; the former is proved by : haking up with toluene, when fatty acid is extracted. The unsaturated Oleic Acid is more soluble than the other saturated soap acids, and the oleates suffer less hydrolysis.in aqueous solution.

The Physics of Oil-Water Emulsions.

Emulsions of this type (and the related oil-aqueous soap variety) are of enormous industrial importance. Apart from the special detergent emulsions, alkaline solutions are added to crude oils for purposes of purification ; the free fatty acids of the raw oils form soaps, and emulsions are thereby produced, often of a very intractable kind. A two-fold division of oil and water emulsions may be made :— 1. Those having the oil as continuous phase and the water as disperse phase, i.e., those in which water is suspended in oil. Such occur in some grease emulsions from seak recovery, in certain oil purifications, and in margarine.

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2. The converse of the above, as in the well-known detergent emulsions of textile scouring; here the water is the continuous, the oil the disperse phase. It is possible to deduce, mathematically, expressions for the volumes respectively occupied by the two phases for suspended spheres or globules of given diameters packed as closely as possible in the continuum. If the globules fill completely the space provided by the continuous phase, the emulsion is said to be ‘‘ The usual industrial emulsions contain less (and some much less) than 50% of the dispersed phase. Thus, if equal spheres are taken, and are piled so that each sphere rests directly on the top of another—the so-called minimum or cubical piling—the voids or spaces may be shown mathematically to be about 48% of the whole volume; this result is independent of the size of the spheres. If, however, each sphere rests in the hollows, i.e., equally on the four spheres of the layer below—maximum or hexagon piling—the investigation shows that the proportion of voids is about 26%, irrespective of the size of the spheres. If different sizes are used, or if the shapes are altered, the volume of voids is . indeterminate and may have almost any value. In lampblack, for example, the solid matter occupies only about 5% of the total volume, and in heaps of loose wool, the situation is much the same. In soap froths, the spherical bubbles form into twelve-sided cells meeting at 120°, i.e., rhombic dodecahedra, a more or less stable condition. A scouring liquor in the wool bowls or a piece scouring machine, is of a composite character :— 1. Coarse suspensoid, in respect of floating flock or dust particles. 2. Colloidal emulsion, with regard to the soap and dispersed oil. 3. Molecular dispersoid, or true solution, with reference to dissolved alkali, etc. Such a medium is miscible with water and capable of great dilution, a property which renders possible a practical scouring process. The successful scourer is concerned only with the chemistry of comparatively dilute solutions, colloidal or otherwise. The inverted type of oil-water dispersoid, i.e., the kind in which water is emulsified in oil, may occasionally occur in practical scouring. Heavily oiled woollens carrying 10% or upwards of spinning lubricant with much free fatty acid, may produce water-in-oil emulsions in the scouring machines. This occurs when there is an exceptionally quick stripping of the oil by the use of rather warm alkali, especially ammonia, with added soap and a comparatively “short” liquor. .The saponification of the free fatty acid and emulsification is so

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rapid in the limited amount of water, which tends to be quickly absorbed by the fabric itself—that the scour inverts. The whole machine becomes greasy and the rollers do not drive, the pieces slipping and eventually stopping entirely. The remedies are obvious and consist of preventive measures ; dilute the alkali, increase the volume of solution, and work at a lower temperature. Run the scour in more than one stage, and dispense with added soap entirely. Omit the ammonia, which is partially responsible for the undue initial saponification. (See later on the Saponification Scour.) The two types of oil-water emulsions are exemplified by milk and butter. If a suitable colour, say Sudan III, soluble in oil is used, such emulsions may be distinguished under the microscope as to the disperse phase and the dispersion medium. Lanolin may be emulsified with water up to nearly 80%, constituting a good example of a water-in-oil emulsion ; another textile example is the greasy magma formed by cracking the waste scouring liquors by sulphuric acid. A further natural case is the greasy suint of the raw wool. Pickering has made similar emulsions by using paraffin and water with small amounts of soap. When the percentage of kerosene was 70-80, the mass was viscous and with 99% of oil it was a stiff jelly capable of being cut up. On exposure to dry air the water evaporated from the soap film, which then cracked, allowing the oil to run out as a liquid. The - mineral soaps of some fatty acids, e.g., calcium and magnesium oleates, will form colloidal solutions in oil and may be used to emulsify water in oil. Certain greases are thus made by adding lime and soap to mineral oils. This action occurs occasionally in textile scouring with hard waters ; deposits of these mineral soaps sometimes form on the interior woodwork of the machines, forming pastes of great viscosity. Accidental daubs from these passing on to the pieces cause unlevel dyeings at a later stage. Brigg’s method of determining the type of a particular emulsion is to add a little water or oil and examine under the microscope ; the one that is the external phase or dispersion medium will mix readily, the other not at all. This is obviously the principle behind the common practice of rubbing a mineral oil bearing-stain on a piece with olein before sending to the scourer; the saponification of the olein by the alkali then disperses and emulsifies the mineral oil into the ordinary oil-in-water emulsion. A first stage of alkali alone is useful in scouring where the water supply tends to be hard, or on “slipe’’ wools and judicious use of caustic alkali is useful. K. L. Griffiths (Jour. Amer. Chem. Soc.), in discussing the nature of oil-soap emulsions, refers to the well-known hydrolysis ef soap in water. In an emulsion of mineral oil with aqueous

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soap, the fatty acids from the hydrolysis are dissolved in the oil; an excess of alkali tends to prevent this. Part of the soap forms unimolecular films around the oil droplets. The average areas occupied by each molecule of sodium oleate, potassium stearate, and potassium palmitate, were found to be 48, 27, and 30 x 10 71® sq. cms. respectively, which agree closely with the corresponding fatty acids in monomolecular films on the surface of water. Emulsions are unstable when there is insufficient soap to form a unimolecular film. Lewis, in experimenting upon emulsions of hydrocarbon oils in water, found a diameter of 4 x 107° cm., which apparently was a critical size, i.e., an equilibrial size, as different methods of preparing the emulsions yielded similar results :— 1. Boiling a small quantity of oil in a large quantity of water. 2. Shaking oil in water. 3. Dissolving oil in a little alcohol and pouring into water. In case (3), the oil must have been aggregated from molecular dispersion as a solution in the alcohol to give the larger particles of the emulsion. 7 : The globular oil formation in such scours as occur in ordinary - working takes two forms :— 1. Fixed globules, not agglomerating with time and which form the permanent element of the emulsion, i.e., its stability. 2. Temporary globules, due to agitation, gas-frothing, etc., readily aggregating to larger globules and_ easily subsidising. The natural oils and fats (glycerides of fatty acids) tend to form globules in aqueous soap solutions of the first type to a greater extent than the hydrocarbon mineral oils ; more olive oil is taken up by a certain soap solution than mineral lubricat- ing oil, a fact having a direct bearing upon the spinning oil problem. In the case of fatty acid attacked by alkaline carbonate solutions, the “ fixed concentration ’”’ is high. In general, the lower the soap concentration and the alkilinity, the lower the percentage of permanently emulsified oil. The effect of alkalinity in an aqueous soap emulsion is to stabilise the emulsion. It is found in attempts to separate oil from emulsions—in oil purification by alkalies forming soaps and in seak recovery operations—that the higher the alkalinity, the more permanent the suspension of globular dispersed oil.

RECENT RESEARCH ON SOAP SOLUTIONS.

Among the methods of research into the nature of solutions is that of their conductivity for electricity. This property is one of the bases of the Ionisation Theory, according to which substances dissolved in water, for example, become partially

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dissociated into their elementary atoms or atomic groups. By these the electric current is carried in such media, and the conductivity of the solution is a measure of the splitting up into the several ions. Many experimenters have found that soap solutions possess a relatively high degree of electrical conductivity in both dilute and concentrated solutions, a degree not completely attributable to the hydrolysis, as was assumed by Kahlenberg and Schreiner, in 1898. Bunting and Martin (Jour. Chem. Soc., February, 1914) made measurements at 90°C. with solutions of the potash salts of the fatty acids from Stearic to Acetic, and found the conductivity to be unexpectedly great ; the curves of conductivity-concentration are anomalous, passing through a minimum in N/5 to N/10 solutions, and a maximum in N/1 to N/2 solutions. The potash or soft soaps had higher conductivities than the soda soaps, but there was a general resemblance in the curves. Prof. J. W. McBain has worked for several years, from 1911 onwards, upon the constitution of. soap solutions, and has put forward an explanation of their structure on the basis of large molecular aggregations ; the following summary is taken from the Third B.A. Report on Colloid Chemistry (H.M. Stationery Office) :— we

‘** Soaps in aqueous solution are intermediate in their general properties, exhibiting the high electric conductivity characteristic of electrolytes and comparable for example to a salt like Sodium Acetate, and on the other hand, osmotic pressures with lowering of the dew-point and freezing-point similar to those of a typical non-electrolyte like sucrose. In concentrated solutions of the higher soaps, the osmotic activity is often only about one-half of that required to explain the conductivity. The form of the conductivity curve is remarkable, and is such as has hitherto been observed only for certain anomalous non-aqueous solutions. Both relatively and absolutely, the con- ductivity is at a minimum between 0.05 N and 0.1 N solution. Thereafter, instead of decreasing steadily with increasing concentra- tion, the conductivity rises to a pronounced maximum in 0.75 N solution. The relative conductivity, as compared with the corres- ponding acetate, has nearly doubled with the same increase of concentration. These unique relationships clearly establish that when such soap solutions increase in concentration, the palmitate ion, for example, is being replaced by some other much _ better conductor of electricity, the ‘ Ionic Micelle. A 0.6 normal Potassium Oleate at O0-18° Cent. is found to contain 0.17 normal potassium ion, not more than 0.01 of other crystalloidal matter, the remainder being entirely colloid as ionic micelle, and comprising 0.16—0.17 normal aggregated oleate ion, with a total of 0.41—0.43 normal aggregated potassium oleate. Colloidal electrolytes, therefore, are salts in which one of the ions has been replaced by a heavily charged, heavily hydrated ionic micelle which exhibits equivalent conductivity that is not only comparable with that of a true ion, but may even amount to several times that of the simple ions from which it has been derived. In other words, this ionic micelle is a typical, but very highly charged, colloidal particle of very great conductivity. When the results for the potassium and sodium salts of all saturated fatty acids from acetic

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to behenic acid and likewise the oleates, are reviewed, the utmost regularity is observed in the gradual and regular transition from a typical curve of an electrolyte presented by sodium acetate through the appreciable deviations of the lower fatty acids (hexoates and caprate), to the laurate, in which a step out or maximum and minimum is first observed (in the case of sodium and potassium laurate respectively). Although potassium and sodium soaps exhibit a close general resemblance, the solutions of the potassium soaps evidently contain rather greater quantities of ionic micelle. Soap solutions are very much more colloidal at lower temperatures than at the boiling-point and the presence of colloid extends into comparatively dilute solutions at 0°C. The formula for the ionic micelle in a Sodium Palmitate solution would be :—

(Na P)x. (P")n. (H, O)m;

indicating a ‘molecular weight’ for the micelle of the order of magnitude of at least 3000, the true value for palmitate being only 255. The viscosity of soap solutions increases with rise in concentration of the soap, at first gradually and then quite enormously ; for instance, Potassium Oleate at 20°C. exhibits a viscosity of 1.19 for N/20, 1.87 for N/5, 8.02 for 0.4 N, and no less than 1563 for 0.6 N, taking water as unity. The effect of temperature in the less viscous soap solutions is practically that of the alteration of the fluidity of water. At 90°C. a normal solution of potassium oleate is 3.8 times as viscous as water at the same mean temperature. Potassium or sodium oleate (C,,) at room temperature is very much more viscous than, say, the myristate (C,,) ; it is probably much like the stearate (C,.), except that the effect of the double bonds is to render it liquid, even at the freezing-point. Added alkali appears to favour the formation of ionic micelle. Soap solutions are remarkable for their bulkiness, a normal solution of sodium stearate being 31% greater than that of a solution of sodium acetate containing the same amount of water. Potash soaps are’slightly denser and ammonium soaps somewhat lighter than the soda soaps, and the highest members of the fatty acids produce soap solutions of the least density. The surface tensions of the various soaps against air, paraffin, oil, benzene, etc., interfaces’ exhibit interesting variations, of which Hillyer has made numerous studies. (Jour. Amer. Chem. Soc.) Even a solution of sodium oleate so dilute as 0.002 N or about 0.06%, will reduce the surface tension of water to less than one-third, and a 0.001 N solution brings it down from 80 to approximately 60 dynes per cm., against air. Hillyer found that in contradistinction to the behaviour of their surface tension against air, the surface tension of sodium oleate solutions against paraffin oil (kerosene) continues to diminish rapidly and steadily with increasing concentration up to decinormal ; it is then only about 5 or 6% of that of water. Deci- normal sodium hydroxide has almost as great a surface tension against paraffin oil as pure water. Rosin soap, whether at 100°C. or in the cold, does not differ markedly from sodium oleate, in surface tension. Care must be exercised in drawing deductions from surface tension determinations of soap solutions against special liquids, e.g., benzene, and extending such results to other interfaces.”

Factors of Detergency.

The intimaée relation between surface tension and detergent action has been already noticed in the section on Surface Tension, Chap. V; it was there stated that a 24% soap solution brings down the surface tension of water against air

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to about one-third of its normal value for pure water. The matter receives further illustration in the section on the Formation of Foams, etc. This factor of reduction of surface tension is undoubtedly one of the principal elements in detergent power. Prof. Donnan’s experiments on the diminu- tion of surface tension in the stearic series of fatty acids are exemplified in this present connection by Bunting and Martin’s research previously quoted. These authors, using warm water and soaps made from the pure acids, noted important differences between the working powers of hard and soft soaps. Potassium Myristate and Laurate are ideal soaps (for washing the hands) ; Palmitate is good, but Stearate is less so. Sodium Myristate (C,,) is good, but Palmitate and Stearate quite inferior. Potassium Hexoate (C,) is a soap only in strong solution ; Potassium Octoate (C,) is still more distinctly a soap; the Decoate (C,,) is the first to raise a typical lather, though this has not much body. Messrs. Allwood and Isherwood (Jour. Ind. Eng. Chem., September, 1916) performed experiments on detergent action and drop numbers, these latter being obtained by the drop pipette. They placed weighed amounts of lampblack on filter-paper, and tested various solutions as to their power to carry it through the filters, which were afterwards weighed. Water and solutions of alkali only, carried nothing through ; solutions of soap and alkali carried lampblack through in amounts increasing with the drop numbers (i.e., increasing with the lowering of the surface tensions); these had been studied by solutions of alkali and soap in a bath of kerosene. One of the chief points of interest im this research is in the fact that it is made on unsaponifiable solid dirt. In a recent paper (Trans. Chem. Soc., 1922, p. 121) McBain and Jenkins have submitted certain soap solutions to ultra- filtration. It is shown that soap in solution contains at least ten molecules of water of hydration per equivalent of soap. By the ultra-filter the separation of ionic micelle from neutral colloid has been effected. The diameter of the particles of ionic micelle is only a few times the length of the molecule, and its approximate formula is :— (Ol’),, mH,0. Whereas the neutral colloid of potassium laurate has particles. less than 15 in diameter, those of sodium oleate are about ten times larger. Adsorption effects must be a further factor in detergency. Spring had performed, in 1909-10 (Zeit. Chem. Ind. Kolloid), experiments on suspensions of fine powders, e.g., lampblack, fine clay, ferric oxide, etc. Even a 2% aqueous soap solution would carry soot through a filter. Compared with purely aqueous suspensions, a 1% solution of soap will carry 206

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times the quantity of clay, and 37 times the quantity of silica through a filter-paper. After observing that a soot suspension deposits its carbon on the negative pole when electrolysed, and that such suspension clears almost as rapidly as pure water, it is stated that the effect is due to adsorption between the soot and the acid soap of hydrolysis ; this latter, on electrolysis, would be deposited on the positive pole. Spring further notes that soot suspensions in water containing a trace of alkali (six parts per million), are much more permanent, i.e., deposit slower than similar suspensions in pure water or weakly acid water.

S. U. Pickering attributes the detergent action of soap to :— 1. The power of emulsifying oil ; the globules are coated with a pellicle preventing them from oiling adjacent objects, 2. The low tension between soap solution and oil. 3. Possibly to the acid soap of hydrolysis forming a colloidal compound with the dirt. The question why the elements—droplets—of an emulsion do not coalesce is also of practical importance ; it is possible to destroy the effect of a scour in several ways, e.g., over rapid dilution, etc. Alkali and soap emulsions are relatively sensitive to dilution ; the “‘ cracking ”’ of an emulsion is a coagulation of the emulsification, probably by the redissolving of the adsorbed matter which ordinarily prevents coalescence. This raises the question whether such emulsions can be stabilised, e.g., by additions of gelatine or other colloids. Colloidal solutions are stabilised by albumen, etc., for medical application. The problem awaits further development. In view of the often repeated proposals to add colloid substances to the scour as stabilisers of the emulsions—gelatin is frequently suggested for this purpose—it must be noted that proteins diminish the power of.soaps, e.g., sodium oleate, to reduce surface tension. Rona and Michaelis concluded that the soaps formed compounds with the protein. Emulsifying agents are commonly employed in the manufacture of mar- garine, as additions to the milk or oil, such as egg-yolk, lecithin, gelatin, albumin, etc. Clayton states that :— “Gelatin is an excellent emulsifier. A palm-kernel oil giving a drop

number of 73 in water at 30°C. gave 120 drops in 1% gelatine. Two samples of oils at 25°C. gave the following results :—

COTTONSEED OIL IN: ARACHIS OIL IN: Water .. .. 66 drops. Water ‘3 66 drops. 0.25% gelatine 124 _ ,, 0.5% gelatine 140 _,, 0.50% Pat. on 1.0% ‘5 4, 1.0% a, 2.0% 4 160.8%; 2.0% + 149: ,, 3.0% 108 iyi 3.0% i 4.0% a 150.0 ,,

The curve given by plotting the results for cotton-seed oil suggests a maximum effect at about 3%.”

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There may be objections to the use of gelatin in this way from the danger of setting up putrefactions, mildews, etc. Further, it must not be overlooked that some mixtures of colloids are incompatible, producing mutual precipitation ; thus soap and saponin solutions are not miscible.

A factor of very great importance in the use of soaps as cleansers is that of their extreme susceptibility to hydration, i.e., their water-holding power. A soap-water system exhibits alf degrees of mutual solubility, ranging from bar soap (which a solid solution of water in soap) down to dilutions of soap in water so great that all colloidal property is absent. This hydration is distinct from a process of hydrolysis in that no splitting of the molecule is involved. When a neutral oil is subjected to the fat-splitting operation, glycerine is separated, and the free fatty acid is reproduced by the hydrolysis. A typical hydration is seen in the case of phenol, which can pass from the stage of pure phenol in crystals by addition of water, through a two-layer system to a true solution of phenol in water; the two-layer stages may pass over at different tem- peratures from water-in-phenol to phenol-in-water. At about 8% phenol ceases to be dissolved, a further addition causing the formation of a second liquid phase containing excess of phenol and a small quantity of water, i.e., a solution of water- in-phenol. If the temperature is raised, this second phase disappears and a further amount of phenol must be added to reproduce it. At temperatures above 68.4°C., however, phenol and water are miscible in all proportions, like alcohol and water at the ordinary temperature, forming a homogeneous solution. Such changes are very analogous to those in soap- water systems at different temperatures.

McBain and his workers have investigated the conditions under which a given soap appears as sol, gel, or curd. The first portions of soap added to water go into solution apparently in the normal way and are probably subject to ionisation, as in ordinary electrolytic salts; at this stage, the resulting solutions have surface tensions differing but little from that of water itself and are not more detergent than pure water. This is illustrated by the table in the section on wetting power and also in the subjoined results :—

SOLUTION. CONCENTRATION. SURFACE TENSION. Water ; — 75 Sodium Oleate 0.025 55 Sodium Oleate 0.25 26 Sodium Oleate 1.25 26 Sodium Oleate Zao 26 Saponin 52

(Rayleigh.)

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At a certain concentration, which depends on the nature of the alkali, fatty acid and temperature, the solution becomes colloidal ; some soap now exists in this as hydrated colloid, molecularly aggregated into micelle. There is a diminished surface tension and corresponding interfacial tensions against solid surfaces, with enhanced wetting-out powers. The viscosity increases rapidly, even enormously, and the solution acquires detergent ability, i.e., it becomes a scour. Indeed, it may broadly be said that a scouring liquor is a liquid hydrated colloid having :—

1. Surface tension about one-third that of water. 2. Viscosity greatly exceeding that of water. 3. Increased powers of wetting-out. 4, Foaming power, i.e., property of forming permanent lathers. 5. Emulsifying property. Some of these, of course, are interdependent. If the concentration of soap is further increased, a solid. gel is finally formed. It is not uncommon when soaps from fatty acids of high melting-point are used in the scouring sheds, to find the soap tanks containing such soap jellies. Indeed, the writer has seen such soap “ solutions ”’ (?) applied to pieces in both scouring and milling operations !

The three types of soap-water systems to which all others may be related are :— 1. Soap Sols; more or less clear and usually transparent liquids carrying some amount of flocculent solid soap, the result of hydrolysis ; the viscosity varies from that of water to values several thousand times as great. To this section belong the working scouring liquors of the textile trade. 2. Soap Gels; as above, but with a definite shape and some elasticity. 3. Soap Curds ; opaque masses, white or coloured, according to composition (resin) and presence of impurities ; are networks of fibres enclosing soap gel or sol.

Pickering states (Jour. Chem. Soc., 1907, p. 2001) :— “In a mixture of machine oil and ordinary water well shaken, the oil is broken up into small drops which, according to the specific gravity of the oil, will rise or fall, forming a separate layer in which the separate drops coalesce as a continuous liquid. Tn a soap solution, on the contrary, within certain limits, this coalescence “sig not occur. The effect is probably connected with adsorption, , high concentration of matter from the body of the solution in he surfaces of the droplets, producing a quasi-solidity and consequent increase in rigidity.”’

Krafft has emphasised the fact that the soap must be in colloidal solution in order that there should be detergent

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action ; thus, in cold water Sodium Palmitate and Stearate are nearly insoluble, while the soluble oleate is an ideal detergent. Hot water is necessary for tallow soaps composed largely of palmitate and stearate. Bain remarks that :— the measurements of the amount of ionic micelle present in various soap solutions the washing power which the oleates exhibit par excellence, is connected with the fact that their colloidal nature persists well into dilute solutions. For this reason, stearate is suitable for washing at the boiling-point, since at this temperature it is soluble and contains much more colloid than the lower _ Hirsch, in 1898, showed experimentally that fatty oils were not more readily emulsified than were various other organic liquids ; neutral animal and vegetable oils are not much more amenable than the paraffins, though in these differences occur between mineral oils of olefinic and true paraffinic type. Such factors are of importance in the blending of wool lubricants for the spinning, etc., processes.

Hillyer (Jour. Amer. Chem. Soc., 1903) showed experiment- ally that the emulsifying properties of soap could not be attributed to hydrolysis-alkali hydroxyl ions, nor did alkali possess the power of wetting oily matter that soap did. Donnan had pointed out that the free fatty acid contained in all natural fats and oils could be neutralised with formation of soap, but this would be quite different from the saponification of glycerides, which is an extremely slow reaction. Hillyer demonstrated again the parallelism of low surface tension and emulsification in soaps, and incidentally showed that saponin emulsified through formation of solid surface film instead of through low surface tension. He further demonstrated the power of penetration into capillary interstices which is conferred upon soap solutions by their very low surface tension. Under the action of soap solutions, dirt and impurities become less adhesive to one another and to the tissues.

His experiments show that the main factor is that of the soap dissolving oils, including paraffin oil, and forming soluble compounds even up to 50% of oil. Excess of water does not decompose this oil-soap compound.

It is necessary to emphasise the importance of the solubility factor for various soaps. A bar soap made from mixed fats could conceivably consist of a mixture of the sodium salts of, say, a dozen fatty acids, e.g., oleate, stearate, palmitate, linoleate, laurate, linolinate, arachidate, caprate, caproate, caprylate, myristate, etc. ; these all of differing melting-points. Now the melting-points of the fatty acids run generally parallel to the solubilities of the soaps. The liquid soaps— oleates and linoleates—are better foaming and emulsifying agents than the higher soaps of the acetic series—the palmitates and stearates—at ordinary temperatures, for the reason that.

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the latter are more solid, i.e., less hydrated, even in the presence of considerable water. At higher temperatures these more solid soaps assimilate their properties to the oleates at ordinary temperatures. Thus a stearate soap is indicated for the process of degumming of silk in the usual boiling bath. Generally, a more soluble soap would require for a given emulsification either a greater concentration or a lower tem- perature, or both; but the increased solubility leads also to more perfect washing out from the fabric, a valuable scouring property in practice. . Those soaps are the best emulsifying agents which at the temperature of their use in the presence of water yield essentially liquid systems of the type water dissolved in soap. Hence the oleates, linoleates, etc., are of all soaps the best emulsifiers at the ordinary temperature, because besides having high hydration values, they are liquids. The higher soaps— stearates, palmitates, etc.—do not foam at ordinary tem- peratures because not enough of them goes into solution to yield a liquid hydrated colloid system. Another way of expressing this point of view in the case of soaps from potash and soda is that a soda soap becomes colloid sooner than a corresponding potash soap, because potash soaps are more soluble in water, and as a result yield molecular (i.e., true) solutions over a greater range of concentration than the soda I soaps. I

The reactions of soaps with indicators are of some interest ; the following notes are due to Fischer (Soaps and Proteins). A chemically neutral Potassium Oleate soap may be prepared by adding the molecular weight of oleic acid, i.e., 282.3 grams. to 1000 c.c. of Normal Caustic Potash solution ; this is alkaline to litmus but colourless to phenol phthalein, when a *‘ neutral ”’ soap has thus been produced by the combination of the necessary gram equivalents of free fatty acid and standard alkali, it is either Acid, Neutral, or Alkaline to such an indicator as phenol phthalein, depending on the concentration of water in the system. Thus the rather concentrated solution of Sodium Oleate made from one mol of fatty acid combined with one litre of normal sodium hydroxide (i.e., practically a molar or 30% solution of the soap in water), is, as above, colourless with the indicator ; and as water is added it becomes pink and with increasing dilution, brighter red.

Soaps, e.g., Soda Stearate, or Soda Oleate, will yield gels, i.e., colloid systems with solvents other than water; for instance, with alcohols including glycerine, also with turpentine, benzene, toluene, chloroform, carbon tetrachloride, and many other liquids. Some of these have applications in particular operations, as for example, in the dry cleaning of garments.

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The General Summary.

of the detergent problem may perhaps be presented somewhat as follows :— In the detergent operation, these actions occur :— 1. Wetting-out of the fabric. 2. Emulsification of the dirt and grease. 3. Stabilising of the emulsion. 4, Dilution of the emulsion. The FIRST STAGE is a function of the detergent material ; in the main, its power of reducing surface tension. The SECOND STAGE involves mechanical displacement of dirt of the solid kind, and the saponification of free fatty acids by alkali. This latter requires either the hydrolysis alkali of the soap or the ordinary alkali of the scour. The displacement of dirt and formation of an emulsion are the result of physical factors, e.g., Brownian Motion, liquid diffusion, osmotic pressure, electrical actions at the ‘* double layer,’ and effects of temperature. These are properties of the medium as a whole, rather than special properties of a particular detergent. The THIRD STAGE is probably largely an effect of adsorp- tion of detergent matter from the solution on to the surfaces of dirt particles or on droplets of saponified oil. This con- densation approximates these droplets to the state of solid matter, involving an increase in rigidity and a gain in perman- ence in the system ; in general, the distinctive properties of a colloidal solution. The FOURTH STAGE involves a resistance to re-solution of the adsorbed matter. A good deal of light will be thrown on the general detergent problem by the establishment of a sound Theory of Dyeing ; the problems of the absorption of mordants and dyestuffs by textile fibres are intimately related to the question of the adhesion of dirt and its removal by the action of soap solutions. Heerman, in a study of the action of mordants, in 1906, considered that “‘ when the Ionic and Electric Affinity Theories shall have become more developed, a satisfactory explanation will be found in them.’’ The purely theoretical question may perhaps safely be left here for the present.

Strength of Soap Solutions.

The natural sequence from a review of the knowledge of soap solutions is the practical question of the relation between concentration and detergent power. It will be seen from the previous discussion that the query, ‘* What is the best strength of soap solution for scouring ?’’ involves the prior question, I ‘Which soap?’’; a problem which includes. in turn the particular alkali, fatty acid, and temperature. Treating the

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problem broadly, it is resolved into :—At what concentration is the sum of the factors of detergency a maximum ? In this form it admits of an approximate answer. Not many attempts have been made to determine the washing power of soaps directly, but there is a general agree= ment in the order of these results, and a fair accordance with average practice, as governed by long experience. Messrs. Shukoff and Scheztakoff, in 1911, in the research previously quoted, prepared standard dirty material by soaking cotton goods in a benzene solution of lanoline mixed with lampblack ; the samples were then dried out. In order of decreasing washing power, they placed :—Tallow soaps, soaps from liquid vegetable oils and oleine, cocoanut and palm-oil soaps, resin soaps. They found that the washing power was a maximum at 0.2-0.4%, or about N/130. Again, Spring (Koll. Zeitg., 1909, p. 4161), experimenting on suspensions of lampblack, found that 1% was the most efficient concentration of soap, giving the greatest emulsifying power ; his results were confirmed by Donnan and Potts, in the same journal, in 1910, p. 7208; they suggested that some electrical factor was concerned. Harrison, measuring the contact electrification between soap solution and cotton, found :—At. N/100, 0.028; at N/200, 0.037; and at N/300, it was 0.013, giving a maximum at about N/200 or 0.15%. Donnan and Potts found an optimum concentration at N/300 soap solution

30 [

l

8

3

Drop INum ber

O Os j VS 20 QS v0

CONCENTRATION OF SOAP (PER CENT) (AFTER “SHORTER? Fig. 32.

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in the emulsification of paraffin oil, and pointed out that the excess of soap in the interface which is a necessary corollary of the reduced surface tension, and the viscous nature of the surface film must both contribute to the stability of the emulsions. And Briggs and Schmidt (Jour. Phys. Chem., 1915) found that the optimum amount of soap for the emulsi- fication of benzene is 1%; this is three times the value given by Harker, viz., 0.01) normal. It has been found in experiments on the action of soap in stabilising suspensions that there is a maximum effect at concentrations of 0.2-0.3%. Now Dr. Shorter has shown from the drop-number results of soap solutions against benzene, that the surface tension varies with the concentration in a distinctive way. Between zero concentration and 0.15%, the drop number is small and. fairly constant, then rapidly rises as far as 0.4°%% and assumes a nearly constant value beyond this strength. The surface tension is not materially lessened in concentrations beyond N/60 or about 0.5%. The drop numbers vary merely with the surface tension, though not in exact variation in soap solution. Thus these more scientific investigations concur in pomting to a _ solution- concentration of something less than 1°% as the most favourable detergent strength; probably 4% is an ideal figure. The common practice in the works roughly approximates to this standard ; in wool scouring, a concentration of 0.7% is advised for the first bowl. Mr. Edw. Lodge, in a lecture on wool scouring, gave 3—5 lbs. per 100 gallons of water, i.e., 0.3-0.5% for a potash soap at 103°F. In piece scouring it is usual to make up 5% solutions in the tanks, and from these 2, 3, or 4 buckets are taken to a machine charge of pieces to be scoured, a quantity of water being already present from the added alkali.

NOTE.

Sodium Oleate, C,,H,, COONa, has a molecular weight of 304. Oleic and Stearic acids have very approximately the same molecular weights, and are monobasic. Hence the relation between the fraction of normality of soap solutions and the percentage by weight is as follows :—

FRACTION OF GRAMMES PER WEIGHT OF SOAP NORMALITY. LITRE. IN SOLUTION. N 304 30.4% N/2 08 0D. 152 16.2 N/5 or 0.2 N 60.8 6.08 N/100 or 0.01 N 3.04 0.304

A 2N sodium palmitate = 2 gram mols per kilogram water = 556 grams sodium palmitate to 1000 grams water = 35.7% by weight.

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Priestman, in ** Woollen in the chapter on wool- washing, gives the following soap and alkali strengths, taking the bowls as 1500 gallons capacity :—

First bowl 120 Ibs. soap 0.80% 40 lbs. alkali O24 % Second bowl 60 lbs. soap 0.40% — alkali — Third bowl 50 lbs. soap 0.37%

The 5% solution of an ordinary commercial soap of 30% content of water will, of course, be about 34% real strength anhydrous soap. In the scouring machine mingled with, say, 15-20 gallons of alkali 2-3°%, its concentration will be con- siderably less. Suppose 10 gallons of the soap solution to be added to 20 gallons alkali, there would result approximately 34 lbs. real soap in 300 lbs. water, or roughly a 1% solution. It thus appears, as in so many other cases, that long practice and observation have arrived at results and routines which scientific investigation subsequently justifies.

EFFECT OF ALKALI ON SOAP SOLUTIONS.

When water is added to a strong solution of soap, the dilution causes a progressive decrease of viscosity. If caustic alkali— NaOH, KOH—solution is added, there is first an increase of viscosity and finally a separation of the soap from the aqueous solution. With ammonia, AmOH, there is neither the gelation nor the secondary liquefaction and separation ; the substitution of base yields a highly soluble ammonia soap, the medium becomes less colloidal, and there is a consequent fall in viscosity. The addition of alkali of any kind to a scouring solution should stop a long way short of any “ salting out ’’ action ; in practical scouring the gel condition of soaps is not utilised, still less the curd stage. Now in the much smaller concentrations the addition of alkali to soap solutions reduces the surface tension, the effect which is utilised in ordinary scouring. There is an increase in viscosity and a rise in the solidification temperature ; perhaps generally a further hydration of the colloid. The related question of how much alkali should be added to the scour cannot be definitely answered. If the amount of free fatty acid in the wool lubricant is determined, a chemically equivalent quantity of sodium carbonate can be calculated. In a Saponification Scour on good woollen fabrics, current practice adopts 4, 5, or 6 times this theoretical quantity. It is not yet investigated how much saponification and how much emulsification occurs in such scouring. It is, however, settled that an excess beyond that dictated by the limit of maximum reduction of surface tension or chemical equivalence is required in practical working. It may be noted in passing that oleate soaps are relatively insusceptible to processes of the “ salting

N

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out ” character ; in seak liquors they are well known to form very intractable emulsions. The use of alkali along with the soap has important results. It has long been known that free alkali in a soap, within limits and under certain conditions, increases the detergent power. The favourable stage of lessened surface tension noted above with soap alone, occurs with added alkali at a lower soap strength. The practical outcome of this is the scouring principally by alkali—soda ash of one-tenth or less the price of soap—and particularly so if the dirt to be removed is mainly spinning oil of high content of fatty acid. In this latter case, the first attack in the scouring process may be wholly conducted by alkali with every advantage. An excess of alkali tends to inhibit the formation of soap from the free fatty acids present or, by “salting out,’ to destroy the emulsions already formed. This upper limit of concentration appears to occur in laboratory experiments at about 1-2% or 2-4°Tw. for sodium carbonate. Current practice appears to indicate a concentration of not more than 6—7°Tw., or approximately 3%, as the most useful average working ; especially where the first scour is conducted with alkali alone, as advised above. Data with regard to ammonia do not exist, but it is certain that its alkalinity in the quantities ordinarily employed is very much lower ; it is possible that it has specific effects.

Evaluation of Detergents.

The point now arises whether it is possible to pre-determine the detergent characteristics of a particular soap or other cleansing material ; in other words, is detergency a property capable of quantitative estimation, and if so, by what standard and in what units are comparisons to be made? The com- parative washing-power tests on artificially dirtied fabrics made by Shukoff and Scheztakoff, cited above, were among the first attempts in this direction. Another series, on the same lines, has given generally similar results :—Tallow, palm oil, cotton-seed oil, and soya oil soaps being the first four ; olive oil soap was markedly inferior. The usual commercial judgment is based upon : a chemical analysis of the soap, and the amount of fatty acid thus revealed. As an indication of washing-power this is grossly fallacious, for many reasons. In the first place, it will obviously fail com- pletely with detergent materials other than the alkali-fatty acid type. Being primarily based upon the theoretic soap (See Chap. IV), having a fatty acid content of approximately 62° in the hard or soda type, it is inapplicable if the other factors of composition are varied, e.g., super-dried soaps are

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manufactured with 88% fatty acid. Further, on simple analytical grounds, it palpably takes no account of imperfect saponification. A better single test is the percentage of combined alkali. Richardson and Jaffe, in a paper on ‘*‘ The Water-Softening (or so-called Scouring) Power of give two analyses to illustrate the fallacy here discussed.

SOAP A. SOAP B. Fatty Acids 63.00% 67.00% Free Alkali 1.48% 0.60%

Combined Soda % 6.83%

On the usual interpretation of the chemical analysis, Soap B is much superior; in point of fact it was about 20° worse, tested both in respect of its lathering power—i.e., the water- softening factor—and by actual trials. Soap A was a good- class curd, Soap B was made from the saponification portion of woolgrease. (Jour. Soc. Chem. Ind., 1899, p. 998.) All the various physical properties of soap solutions have been employed to measure detergent power. Thus the solu- bility has been used, indicated by the time taken to dissolve under standard conditions of temperature, quantity of solvent, and mode of employment. The tenacity of a soap jelly of standard concentration has been suggested. The. protective action of the soap in stabilising colloidal gold solutions and its effect on the Zsigmondy “* gold number ”’ is another proposal.

GOLD NUMBERS FOR DIFFERENT COLLOIDS.

Sodium Oleate 0.4-1.0 Sodium Stearate (added boiling hot) ° 0.001 Sodium Stearate (added at 60°C. 10.0

The ‘ Gold Number” is the number of milligrams of a protecting colloid which just prevents the colour change in a 10. c.c. red gold solution, containing 0.0053-0.0058% of gold, when I cubic centimetre of a 10°, sodium chloride solution is added. It is interesting to note in the above table :— 1. The superior colloid property of the Oleate over the stearate at ordinary temperatures. 2. The gain of colloidal property by the stearate at the higher temperature. The extended use of the drop-pipette—originally based on experiments of Lord Kelvin—in researches on surface tensions between liquids, by Donnan, Hillyer, Shorter and others, has led to its advocacy for the present purpose. Hillyer proposed to use the drop numbers of a soap solution in kerosene against the standard drop number for sodium oleate in cold water and sodium palmitate in hot water, as a measure of detergent power; and a similar suggestion using benzene has been put forward by Shorter.

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Clark’s foam method for estimating the hardness of water by a standard Pot. Oleate solution, has served as a basis for other systems of detergency evaluation. Stiepel measured the volume of froth produced under definite conditions by a known solution of the soap. Messrs. Richardson and Jaffe, in the communication above, used a standard hard water of ten times the Clark unit (i.e., 2.287 gms. Ca C O, in dil. H Cl and diluted to 1000 c.c.). On 10 c.c. of this—made up to 100 c.c. with distilled water—titrations of 1% solutions of the soaps under examination were made; the frothing, permanent for five minutes, being taken as in hard water testing. This foam value, i.e., the number of c.c. of this 1% solution, was taken as the ‘‘ Scouring Power ”’ degree. Obviously this system approaches a good deal nearer to the actual conditions of employment of soap detergents than the purely chemical or physical methods above. Before a soap of the ordinary type can scour in an industrial water, the hardness must be neutralised; the method uses this water-softening power as the index of detergent efficacy. While this is probably a much nearer approach to a quantitative system than many of the methods already cited, it may be doubted whether it is in itself a complete criterion. It will obviously fail where the detergent material is not a soap in the chemical sense, e.g., in the newer cereal soaps ; yet these have undoubtedly consider- able washing power. Again, soaps are almost universally used in textile scouring with alkalies, often in great excess; a ‘* scouring-power ”’ number obtained in a water-softening test would cease, under these circumstances, to be comparative in the same way; and also, if temperature is neglected, close comparisons are impossible. Still, the method undoubtedly gives results in general accordance with known data; a few determinations are

appended.

FATTY FOAM VALUE. SOAP. ACIDS. (Water- softening power.) Entirely Tallow Curd 64.0% 108% Oleine 62.0 100 Entirely Resin Soap (cold process) 65.0 52.0 Green Olive 64.7 101.8 do. 67.8 103.7

Probably, as the authors remark, “if only one test was available for judging the value of a soap, the water-softening or ‘ scouring-power ’ degree would be unhesitatingly By saponifying fats and oils and taking the as above, the authors have compared the relative values of a number of soap bases ; taking pure Stearic Acid as standard :—

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197 Pure Stearic acid 100 Pure Oleic acid 100

Tallow 95.6 Olive oil 93.2 Cotton oil 87.0 Palm oil 85.0 Coconut oil 79.0 Resin (crude) 58.0 Wool-grease (sap. Linseed oil 35.5 part) 37.0

A table of considerable interest. McBain and his assistants (See Jour. Phys. Chem., 1924, 28, 1-11, and Jour. Soc. Chem. Ind., 1923, 42, 373-378T) have further developed the method of carrying finely divided carbon particles through filter-paper by soap solutions into a direct and standardised process for determining detergent power. This gives a “Carbon Number ”’ characteristic of the material and solution. They show that there is an optimum concentration in moderate dilution for each soap, for which the effect is a maximum; slight additions of either acid or alkali enhance the detergent action very greatly. A curious result is that rise of temperature diminishes the detergent power at first rapidly and then slowly, but there must be a sufficiently high temperature to dissolve the soap. Once in solution, the differences, e.g., between oleates and myristates, are slight. In applying the McBain variation of the Spring method, one gram of a finely powdered carbon is shaken up with 20 c.cs. of the soap solution, allowed to stand 23 hours in a thermostat, shaken again, allowed to stand 1 hour, and then poured on to an 11.3 cm. No. 31 Whatman filter-paper. The filtrate is collected until approximately 10 c.cs. have passed through. This filtrate is then examined either gravimetrically or colorimetrically, and the amount of carbon is taken as the “carbon number” of that soap. The method is really a standardised variation of the system of weighing the solid residue of a known volume of the scouring liquor, which has been previously proposed and utilised as a measure of detergent efficiency. Heermann prepared an artificially soiled fabric by immersion in a $% solution of 20% colloidal indigo paste, then pressed until it retained its own weight of liquor ; comparisons were made on a basis of final shade.

The Mechanism of Removal of Dirt from the Fibre.

How is the dirt attached to the surface of the fibre actually removed therefrom, and how is it carried in the scouring medium? Plainly, the different forms of ‘‘ Textile Dirt ”’ (See next Chapter on Practical Scouring) cannot all be affected in the same way, and their displacement from fibre to scour must be due to different agencies. Water-soluble matter, such as the potash salts of raw wool, etc., is directly removed by the operation of the laws of ordinary solutions. Saponifiable

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oils—-especially free fatty acids—undergo chemical neutralisa- tion into soaps, and their solution follows as above. This action is powerfully aided when the alkali is a carbonate by the liberation of carbonic acid gas in the greasy film; the formation of innumerable bubbles of this gas in situ must be a potent detergent factor. The swelling of the textile fibres themselves in the liquid is also a cause of displacement of matter from the surface, and all particles small enough to be affected by Brownian Motion will have their removal into the liquid medium thereby facilitated. It is an established fact that grease particles are carried in the scour by coating with a superficial layer of soap, which prevents their reunion and

BIG. oa.

Fig. 34.

MECHANISM OF EMULSIFICATION. Sketched from Micro-Photographs.

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coalescence, and thus constitutes the emulsion. It has been shown in the section on solvents that bodies capable of reducing surface tension will, when brought into contact with oil or grease films, effect their disruption and disintegration. Such substances, lowering the interfacial tension of the liquid medium of the scour and the solid exterior of the fibres, creep by diffusion and capillary action between particles of dirt and the walls of the fibre, and thus displace the solid forms of dirt—soot, sand, fibre flock, etc.—floating it into the scour. Electrical actions also play a part in displacement of superficial dirt. For example, a wool fibre and particles of solid dirt on its exterior when immersed in water become negatively charged. (Helmholtz Double Layer.) As an illustration, cotton in hydrochloric acid shows electromotive forces of the order of 1/100 of a volt. In alkaline scours, these negative charges on the fibres are increased ; in acid media they are decreased or even reversed. There will, however, between the negatively charged exterior of the fibre and the similarly charged dirt particle, be the usual electrical repulsion and consequent tendency to displacement and separation. The mechanical movement of the material is another factor promoting dis- placement of dirt, and a further one is the formation of the bubbles of a froth and their incessant rupture and re-formation by the splashing and aeration of the scour. It is therefore not difficult to see why dirt of all kinds is displaced from the fabric, and the general properties of the emulsion discussed in the foregoing sections explain its retention in the scouring medium and its ultimate expulsion from the machines.

SCOURING TESTS AND EXPERIMENTAL TRIALS. It is easily practicable to carry out simple laboratory experiments on detergent operations, e.g., comparisons of soaps or special cleansing materials, or even alternative methods of working. Some standard “ dirty material ’’ prepared so as to give uniform working conditions is the first requirement, and this is generally met by soaking white cotton or worsted cloth in solutions containing lampblack, rouge, etc. Benzol shaken up with lampblack has been used ; lanolin, oleic acid, etc., may be added for special objects. The strips of cloth are passed through the mixture as often as desired and hung up to dry. The cleansing tests may be made by simple immersion in the medium under examination or by warming, or by enclosing in a corked vessel and attaching to a shaking machine or by similar devices. The comparison of the efficiencies of the media is then made by the relative reduction of shade of the samples, and also by filtering the baths and comparing the filter-papers.

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RETENTION OF SOAP AFTER SCOURING.

It is essential that the materials used as detergents should not themselves leave residua in the wool, yarns or cloths, put through scouring routines. Yet finishing faults primarily caused by imperfectly cleansed material are very common. Excess of re- tained soap, over alkalinity due to concentrated soda solutions, uneven scouring due to the use of special detergents such as_ sul- phonated oil, etc., are quite frequent occurrences in ordinary textile work- ing, and it is important to know how far the cleansing materials are removed at the close of the scouring process.

Fig. 35. SOXHLET APPARATUS. (Large Model.)

SOAP IN THE FABRIC AFTER SCOURING.

A. Woodmansey (Jour. Soc. Dyers & Cols., 1919, p. 169) conducted some experiments on ‘* The Absorption and Reten- tion of Soap by Wool.’ Some commercially scoured cloths extracted by petroleum ether after a short treatment by mineral acid showed the following results :—

FATTY FATTY TYPE OF CLOTH. MATTER, % ACID, % Merino Serge (Average of 19 tests) 0.17 1.03 Shoddy Cloth ‘ee 0.25 Worsted Cloth i 0.56 0.20 Flannel 0.20 0.50

It was proved that wool (a crossbred serge) was capable of absorbing fatty acids from 4% Castile soap solution ; and, in

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a lesser degree, silk and cotton; and it was further proved that fatty acid was retained strongly, as in the following experiment :—

A length of crossbred serge, after immersion overnight in a 4% Castile soap solution at 14°C., was progressively scoured in moderate quantities of water and samples taken between each treatment for analysis :— FATTY ACID CONTENT, %

In original .. 0.86 After rinsing in cold distilled water .. 0.80 After boiling 7 min- utes in tap water 0.50 After boiling 30 min- utes in tap water 0.41

There is also absorption of the basic constituents of soap.

** Not only was there pronounced adsorption of the basic portion, but this occurred in greater ratio than corresponded with the simultane- ously absorbed fatty acid. In other words, an acid soap remained in the bath.” The well-known phenomenon of hydrolysis or water-splitting of soap in aqueous solution is closely connected with the present question. There is a preferential adsorption, the wool taking in relatively more of the alkali than the fatty acid, which has led to the older statements that there is forma- tion of an “‘ acid It is extremely doubtful whether such compounds have a real existence, or whether there is anything beyond an emulsion of fatty acid in hydrated soap. (See Fischer, Soaps and Proteins.) The sorption, or taking-up, of the alkali by the wool fibre is probably a chemical reaction ; such a combination is well known in the protein substance Casein. It is more probable that the fatty acid retained by the wool is precipitated on the exterior of the fibre, and it may be accompanied by actual soap. The use of alkali along with the soap appears to counterbalance this preferential sorption by the wool tissue (Griffiths), and maintains the stability of the scouring bath. It is a common device of the practical scourer to recover a “ soap liquor by a little extra alkali, usually ammonia. In this connection, the discussion in Chapter IT, on the dissociation of alkalies and the “ causticity ”’ thus produced is very relevant. Where continuous addition of detergents is possible, as in the scouring of raw wool, it may be beneficial to feed in small quantities of caustic, as against carbonated alkali. It therefore seems to be confirmed that there is a residuum of superficially retained fatty acid and possibly soap—or “‘ acid soap ’’—on the wool fibre after scouring, and that this normally passes through the washing-off without being wholly removed.

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It probably amounts in practical working to 4%, sometimes much more in bad practice. The use of specially added alkali to the wash-off waters—some ammonia or weak soda—will tend to diminish this retained matter. It is reeommended in the chapter on Practical Milling to add soda when lathering up, prior to the wash-down stage. Some indication is also gained upon the re-use of scouring liquors in working on fresh material. It is the orthodox principle in wool scouring to pass the liquors from the cleaner bowls successively forward to the earlier and dirtier members of the set; and in piece scouring, the second scours of a ‘‘lathering-up stage have been utilised as first scours on fresh dirty goods. It is patent that there are limits to this procedure ; scours over saturated with hydrolysed fatty products will lose their cleansing capacity. Some experimental facts indicate that the different fatty acids are not equally sorbed by the fibre, and it is possible that such used liquors might be revived by an active saponifying alkali like ammonia ; if the soap had been originally of the oleate type, some caustic soda would be useful.

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PRACTICAL SCOURING.

Page 229

CHAPTER VII.

Practical Scouring.

What are the objects sought to be attained by the scouring process ? Undoubtedly the principal end is the enhanced appearance obtained by the removal of the dirt; this is mainly due to the gain in brightness and lustre, and improved reflection of light from the fabric. Among secondary results are :— 1. The increased cleanliness from the sanitary standpoint as material for clothing. 2. The gain in permanency of the fibre ; a clean material is less liable to agents of decay, moulds, bacteria, etc. 3. In some cases, improved physical properties, e.g., tensile strength, elasticity, over the unscoured material. 4. Handle; including softness, absence of greasy feel, resilience.

TEXTILE DIRT.

As in other cases, so also in textiles, ‘““ DIRT ”’ is ‘‘ matter in the wrong place.’’ Thus, the wool-fat is a necessary com- ponent of raw wool as it occurs in the living fleece, but in the manufactured yarn or fabric its complete removal is essential. What then is “ dirt ’’ from the textile point of view, or, con- versely, when is the wool really clean? The question of the nature and amount of residual matter in fabrics after the scouring operation will receive separate consideration, but for the present absolute cleanliness in wool may be defined as consisting in 100% of pure fibre—wool, cotton, or silk, etc.—- on the dry weight of material, or 100% fibre together with the normal quantity of moisture. For example, surgical wadding, though scarcely a fabric in the ordinary sense, is a standard of absolute cleanliness in the present aspect ; some types of surgical wrappings and bandages are other instances. Compare the use by the chemist of extracted filter-papers as pure cellulose. Thus finally, a perfectly clean cloth would contain nothing but textile fibre and water of condition, with or without dyestuff; commercial fabrics do not in general approach this standard by several per cents., though of course

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by weighting, loading, proofing, .etc., they may depart inten- tionally very greatly from it. The sources of contamination of fabrics are as varied as the varieties of textile fibres them- selves, and are added to by the artificial conditions of transit and manufacture. A classification of textile ‘“‘ dirts’’ from the scouring standpoint might run as follows :— 1; CHEMICALLY INACTIVE, and usually amorphous : such as carbon particles from singeing, sand, soot, and mineral matter generally ; fibre dust or “ 2. WATER-SOLUBLE MATTER, often crystalline: the potash salts of raw wool, common salt, the mordanting salts, sodium sulphate in acid dyeing, sodium carbonate as neutralising salt after carbonising, etc. 3. SAPONIFIABLE GREASE, FAT, or OIL, partly in the natural wool-fat, but mainly in the teasing, combing, and spinning oils, and containing as the distinctive feature, fatty acids—oleic, stearic, etc.—capable of. saponification in the scour. I 4, NON-SAPONIFIABLE GREASE or OIL: mineral oils of the petroleum industry, ranging from greases like vaseline through machine lubricants to paraffin lamp-oils, characterised by absence of glycerides or similar saponifiable constituents. 5. COLOURING MATTERS natural and artificial: the I ordinary fibre-pigments of wool, tussah silk, ete. ; loose dye-stuffs, as the superficial indigo removed by fullers-earthing ; dye-stains; blood-stains on sheared

wool, etc. 6. “CHEMICAL” DIRT: notably lime in sliped wool ; ‘““ochre’’ stains from iron contamination; many

machine stains, e.g., from corroded brass or copper surfaces ; mineral soaps from hard waters ; unneutral- ised acid from the carbonising process, and the like.

SIZING SAPOMIFIABLE. SALT SOOT oR MINERAL OL ND Vie

ie a = Sok

Fie. 36.—THE “Dirty Fasric.” [Diag.!

There are also composite cases in which products occur belonging to more than one subdivision of the above classification. Machine oil from bearings usually carries metallic matter; mildews contribute colouring matters often of a very intractable kind. In certain cases, dirt of a special

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character is the subject of an individual process, e.g., the cotton-wax by the lime-boil, silk-gum by the soap-boil, fibre- pigments by the bleaching processes, and grease by the special solvent-extraction methods.

The Scouring of Raw Wool.

The raw materials of the worsted and woollen trades are of the most variable kind, fleece wool containing 30-80% of impurities. From the bale of raw wool to the merchanted piece, the fibre may undergo scouring processes as wool, sliver, yarn, and greasy, dyed, or milled cloth, while in addition it may be subjected to several other moisture treatments, e.g., conditioning, carbonising, bleaching, dyeing, crabbing, boiling, blowing, steaming, etc. There exists an enormous mass of technical detail in the various operations, and the present discussion will be concerned with the principles of and the reasons for the different routines. In particular, matters adequately described in other quarters, e.g., the numerous varieties of textile plant, as made by sundry machine makers, etc., will be omitted. The theory of the relations of wool to water—both as liquid and vapour—will receive separate explanation, because of its partial neglect and great importance in the trade literature. The foreign matter of wool, as it is delivered to the scourer, may be classified under four heads :—

1. Mineral matter; sand, earth, mechanically attached to

the fibre. 2. Vegetable matter; straws, fragments of plant tissue, commonly called “‘shives’’; bits of seed pods, ete., commonly called ** burrs ”’ ; portions of vegetable fibre

from the baling material, and similar substances. 3. Wool Perspiration or Sweat; Fr. ‘‘ Suint.’”? The dried excretion from the sweat glands of the skin, consisting largely of potash salts or organic acids, and easily soluble in water. 4. Wool Fat or Yolk. An impure lanolin, insoluble in water, but generally soluble in the organic solvents ; an unsaponifiable material, except by special laboratory methods. As in some cases only one-third of clean fibre is obtained, special methods of dealing with the enormous amounts of dirt are necessary. Wools containing much mineral matter may receive a preliminary opening and dusting out to prevent undue fouling of the scouring liquors. The vegetable matters require either a carbonising operation, or actual removal subsequently by hand from the woven cloth, burling”’; or by mechanical burring. There are two principal systems of

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removing the intrinsic impurities of the fleece—the wool-sweat and grease—viz.: I. Solvent processes. II. Scouring methods.

THE SOLVENT PROCESS.

Reference to the table of solvents and their properties, in Chapter IV, will show that very few of these can be available for the processing of raw wool. Cheapness is essential, and after many trials—carbon tetrachloride, carbon bisulphide, etc.—the present day extraction utilises light mineral spirit or petroleum naphtha. The system is in working on the large scale in America with nearly thirty years’ experience behind it, and to a limited extent in this country. It should be noted that it is really a two-stage process, as a mild warm scour follows the solvent stage. The chief objections are :— 1. The high cost of special plant. 2. Dangers of fire or explosion ; the modern plant is worked by means of inert non-combustible gases such as carbon dioxide circulating in the system. The claims made for the process are :— 1. Gain in weight of clean fibre secured from the raw wool, as compared with ordinary scouring. Reduction of noilage in the combing, on account of no breaking of staple and absence of matting and felting. Kconomy in soap and alkali, etc. Use of the wool oil lubricant in place of olive oil in the later stages of manufacture. 5. By products, e.g., wool fat and potash salts are recovered and can be sold. 6. Superior working qualities of tops and yarn. Lots of 1000 lbs. weight can be handled in two hours, and it is stated that on tests of 25,000 lbs. the solvent treated wool yielded 10° more cloth. An interesting point arising out of the solvent methods is the question of amount of residual matter left in the wool. (See paper by H. Hey, Jour. Soc. Dyers & Cols., 1919 and 1921.) It is found undesirable in practice to carry the extraction to the limit, as the wool becomes harsh and brittle and loses elasticity. This is overcome by the final bath of solvent carrying a known amount of suitable grease, and thus a limit of, say, 0.2% or otherwise, may be perfectly controlled.

WOOL SCOURING.

As the wool sweat is fairly soluble in water, a great deal may be removed by simple steeping, a process long favoured on the Continent and spreading in this country ; 20-30% or more of woolimpurity can thus be got rid of. The raw wool is subjected to a series of, say, half-a-dozen wash waters, preferably warm, passing in succession over batches of wool and thus becoming

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(View from Feed end.) (PETRIE & McNavent, Lrp., RocHDALE.)

37.—AUTOMATICALLY SELF-CLEANING WOOL-WASHER.

Fia.

concentrated in potash salts, which may, if cost permits, be recovered. The subsequent soap baths are protected against over-fouling, but an additional stage of working is introduced, and costs thereby raised. There are several modes of working : 1. Several tanks are arranged at different levels ; the wool is packed in cages, which are lifted by cranes from one

0

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tank to another ; the liquor is piped, when replacement is necessary, to the next tank in the series. 2. Alternatively, the wool is placed in a series of vessels and the liquor flows through these in succession.

3. The wool is carried on a travelling lattice-work over a bowl divided into compartments ; the water, etc., is pumped from the bowl and sprayed over the wool. The separate compartments and pumps enable the dirty liquors to be applied to the most impure raw material, the last bowl receiving fresh water only (Malard machine). As the time of passage through the machine is not more than ten minutes, it is certain that the cleansing action is superficial only. The wool fibre is not fully swollen in such a time at the tempera- ture of working, 90°F. In the ordinary methods of scouring raw wool, long troughs or cisterns, termed wash-bowls—usually made of cast-iron plates—thirty or forty feet in length, capacities up to 2000 gallons, are used, generally in sets of three or four. There is infinite variety in the arrangements of different machine makers, but the following appliances, in one form or another, are usually employed :—

a. Double tanks; the inner with perforated walls or a floor of grids, contains the wool: the outer or lower com- partment is a settling chamber for heavy dirt, and is fitted with channels and outlet valves. b. Feeding devices: usually travelling aprons of lattice wire or laths. Immersion rollers or boxes, ‘* duckers,”’ are fitted at the entry end of each bowl and filters, etc., at the exit. c. Propelling mechanism: consisting of rakes or narrows or forked plates, driven by chains, gears, cams and cranks, etc., to move the wool forward in the bowls. d. Side tanks: for receiving the unexhausted liquors from the press rollers, settling and skimming the same, and returning by pumps to the bowls. e. Squeeze rollers: to nip the wool free from dirty scouring liquor before delivery to the succeeding cleaner bowl.

THE DETERGENT PROBLEM IN WOOL SCOURING.

It is easy to see that the cleansing of wool in the form of dirty fibre has many special difficulties, of which the chief is that there must be little or no felting action, i.e., of the matting together of the wool fibres. This introduces many limitations into the process :— 1. A minimum of relative motion between the fibre and the scouring liquor.

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2. Mechanical squeezing action must be avoided as far as possible. A fabric run on a dolly scourer might get squeezed between the rollers 50-100 times during the scour, while wool fibre receives three to four com- pressions only. 3. Foaming and frothing of the scour cannot be encouraged.

(View from Delivery end).

Fie, 38.—AUTOMATICALLY SELF-CLEANING WOOL-WASHER. (Perrier & McNavent, Lrp., Rocupate.)

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Fie. 39.—WOOL SQUEEZING MACHINE. (JAS. BAILEY, SLAITHWAITE, HUDDERSFIELD.)

Now the frequent displacement of scouring liquor from the surface to be cleansed is one of the most powerful aids to efficient washing; the wool bowl is relatively inadequate in this respect. An alternation of saturation, mechanical ing or draining and resaturation is a desirable cycle in a scouring process. It occurs in wool washing only at the end of each bowl! before transference to the new liquor. On the other hand, the high state of subdivision of the material—the individual fibres of wool have diameters of the order of 1-2 thousandths of an inch—facilitates the attack of the detergent liquid. Again it must be admitted that the special dirt of raw wool is not of the most intractable kind. The wool grease, an impure lanolin, is a readily emulsifiable fat and the suint is freely soluble. The melting-point of wool fat is approximately 40-45°C. (104-113°F.). This raises the question of the temperature of wool scouring, and for convenience some average practice in the use of detergents may be tabulated therewith :—

BOWLS. DETERGENTS. TEMPERATURES, I Alkali and Soap 120-130°F. II Alkali and Soap ner. III Soap 100°F.

IV Water 90°F.

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But there is the utmost variety of practice between different wool-washing sheds, both in materials and temperatures, just as in piece scouring. Now it is clear from the nature of the impurities that the cleansing of raw wool requires an operation of the kind described later in this chapter as an Emulsification Scour. There is in this case no free fatty acid to attack by saponification, and mechanical action is precluded by the necessity of avoiding felting. Hence, every factor tending to the formation of perfect emulsions must be utilised. One of the worst obstacles is the relatively enormous amount of dirt to be removed, and the consequent difficulty in preventing quick fouling of the emulsions. It is plainly desirable to free the wool from mechanically adhering dirt by preliminary beating, and also by steeping wash away soluble matter; this view being concerned only with scouring efficiency and not with costs of working. It appears further that machines which permit of continuous removal of the settled sand, dirt, etc., from the bottom of the bowls—by the action of a slowly revolving worm or otherwise—are preferable ; the intermittent discharge and clean-out of large wool bowls is, at best, an imperfect mode of working, and it is well known that wool washed towards the end of a run is less clean than that passed through in the earlier stages. Indeed, such variations may amount from 1% to 5-6% of foreign matter. The theoretical discussion of the detergent action of soap solutions shows that their utility ceases when, by adsorption of matter in the interfaces of the colloid, a certain maximum has been reached. This sets a boundary also to the re-use of liquor which has already taken part in the scouring process. But experience has shown that it is quite practical to remove continuously the precipitated sediment from the bowls and sustain by frequent additions of fresh detergent substances, the scouring properties of the bath ; and with corresponding advantages in economy of working and uniformity of output and product. The employment of alkali in the scouring of fleece wool is a question of technical interest. In general, the main functions of alkali in textile washing operations are :— 1. Saponification of free fatty acid. 2. Lowering the surface tension of the soap solutions. 3. Softening action on the water. In these respects, caustic as against carbonated alkali is more potent, but it has a distinct browning effect on the wool, and in greater concentrations at higher temperatures, soon attacks the fibre. Now the whiteness of the wool on its emergence from the scouring set is one of the fashionable indications of its cleanliness, especially to the topmaker and spinner, and hence the use of caustic soda, for example, has

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never been very popular with wool scourers. It is, however, fairly well established that, judiciously used in moderate strength, it is a valuable addition to the earlier bowls. In the first bowl of 1800 gallons, along with 25-35 lbs. soda-ash, add, say, 5 lbs. of caustic soda as an initial trial. Whether wool is satisfactorily scoured by the use of alkali alone in the first bowl is a different problem. Some practical trials point away from this, and in view of the known nature of the wool impurities, it is perhaps desirable to use some soap from the start and induce emulsification straight away. It is probable that in an alkali bath alone a slight saponification of the wool grease occurs and the fat becomes “set ’’ as the scourers say; the phenomenon is analogous to the formation of “‘ curds’ in soap making. The use of the softest available water is very necessary, and its general character should be known ; modification of the scouring materials may then be made to secure the best results. The general operation of raw wool scouring is an exceedingly interesting detergent problem, and offers some instructive contrasts with the routine of piece scouring. It is true that solutions of alkali only have some scouring power over and above that of pure water, but it is not perfectly clear why this is so ; there is preferential sorption of caustic soda by wool and an enhanced hydration and swelling of the wool tissue. Lord Rayleigh’s experiments demonstrated the almost universal presence of greasy films on the surfaces of solids, even short exposure to the atmosphere causing contamination. Possibly the alkali acts upon this film, or in the case of colloids, like the textile fibres, the alkali may lower the surface tension of the solid; the swelling is perhaps the initial stage of a process of dispersion. The common practice is certainly in favour of omitting alkali entirely in the later bowls of the set, probably with the object of getting maximum whiteness and softness in the wool. But there are few or no water supplies of absolute or zero hardness, and a proper addition of alkali acts protectively against the hardness of the water, lowers the surface tension of the soap solution, and thus secures a better cleansing of the wool from residual matter. A wool scourer must use observation and judgment ; the quantity of alkali required for greasy or washed fleeces must be considerably increased for skin wools and nearly doubled for slipe wools. In wool scouring, as in other branches, Fines is great diver- gence in the routine of different sheds. It would be an economical and efficient practice to adopt—and manufacture on the spot—olein soaps, which work very well under the conditions of the wool bowls. The concentrations of soap and alkali vary greatly, but the following data represent an average case :—

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Bowl I 1800 gallons Soap 0.75% Alkali 0.25% Bowl If... ,, 55 0.50% js AA Yo Bowl III 1000 __ ,, ig. a Ua Bowl IV Water only. But there is much variation, depending on the kinds of alkali and soap used, and on the varieties used, and also on the qualities of wools scoured. Tinting with Methyl Violet, etc., is often practised in the last bowl ; it has no real utility, and reliance should be placed on the properties of well-cleansed fibre other than mere whiteness. Temperature should be well controlled and the scourer of wool must invariably work to the thermometer, each bowl being fitted with an instrument. It is not uncommon to find the first bowl run at 140°F., but it should be borne in mind that the wool grew on the sheep’s back at a body temperature of about 98-100°F. It is bad practice for scourers to copy the ways of the dyers, whose long boilings of the fibre with strong chemicals, however necessary for fastness, do not enhance the softness and handle of the wool. Loss of spinning property and diminished yield follow from excess in wool scouring, either of temperature, working, or detergent materials. But Colledge (Jour. Text. Inst., 1921) scoured yarns for half an hour in 5% soda-ash as follows :—One at 100°F., two at 140°F. and three at 180°F., and found the loss of strength at 180°F. I only 4%, as compared with 140°F. He continues “I may say that a man may scour many qualities of wool at 160 to 180°F. without detecting which is which, in feel or handle.”’ SLIPE WOOLS, i.e., wools which have been stripped from the skin by the use of lime, are a separate and difficult case to the scourer, the lime breaking down the soap emulsion and forming the mineral soap discussed in the section on hard waters. Such wools may contain several per cents, 6—-8%, of lime, an amount equivalent to about 2 lbs. per pack of 240 Ibs. wool. It is absolutely necessary to put such wools through the willey and remove mechanically as much as possible of the mineral matter. From the scientific aspect, the next process should be an acid bath, the choice of acid being that which yields the most soluble lime salt for the least cost. Common vitriol or sulphuric acid forms Calcium Sulphate, a compound of slight solubility, one part in 450 of water. Spirit of Salt or Hydrochloric Acid at 14°Tw. forms Calcium Chloride, a freely soluble substance, even deliquescing in the air. A suggestion has been made of using Sulphurous Acid, H,SO,, for this purpose ; in this case calcium sulphite is formed, which has some solubility in solutions of Sulphurous Acid, and the wool would be partially bleached, All these propositions have grave difficulties, special plant being necessary, the tanks having to be made on the lines of

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carbonising bowls; the two latter acids being volatile, their vapours cause much corrosion. In all cases of such acid treat- ments, the wool is left in the acid condition and a process of neutralisation must follow, to enable the wool to be after- wards scoured in the ordinary way. limey wools which do not pass through an acid bath, the first treatment must be by alkali alone, and there should be caustic as well as carbonate present. Caustic alkalies have some power of decomposing the lime soaps, and as these wools are already much yellowed or browned by the alkaline lime, the further browning action does not matter so greatly. In any case, the subsequent dyeings control this matter of initial shade of the wool ; its state of cleanliness is much more important.

The soap-alkali system of cleansing wool causes some loss of strength in the fibre, and some experiments made on individual fibres—not on yarns, which would be fallacious— show diminutions of tensile strength amounting to about one-quarter. Even simple steeping, apart from specific effects of alkali, causes some loss, perhaps due to the removal of the superficial fat and suint.

Backwashing.

This operation is a scouring process applied to the fibre in the form of slivers from the carder intended for worsted tops.

The objects are to get rid of any dirt left in from the wool scouring, together with the oil applied to the fibre and any dust or similar contamination—“ top dirt,’’ as it is sometimes called, i.e., superficial dirt—acquired by the passage through the cards. Such matter, allowed to remain, tends to accumu- late on the flyers, caps, and rollers, to wear out the pins of the combs and choke machine parts with greasy dirt, producing slubs and lessening output, while reducing quality.

While these are the reputed advantages, strongly stated, of the operation, it cannot be denied that the main purpose is to obtain an improved shade, i.e., superior whiteness in the tops. This raises an interesting technical question, and following thereon the general usefulness of the backwashing process. The commercial value of wool tops is assessed on the following features :—Fineness, length, soundness, and lastly COLOUR. In this last factor, colour is taken as indicating wool quality ; indeed, over the whole range of wools, there does exist a parallelism of Quality and Colour, the finest being the whitest. From the lowest crossbreds to the finest merinoes, the transi- tion is from butter yellow through creams of varying depth to white. (See Chapter XII on the Intrinsic Colour of Wool.) It is also perfectly true that wool defective in several ways will

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usually be of lower shade. (See section on the Browning of Wool.) Diseased wool, carbonised, overscoured, scorched or overdried, and dirty wools, all show a lowering of shade, and so far a lack of whiteness may reveal poor material. But it is fully explained in other sections of this book that alkalinity in the wool substance is directly connected with a yellowing or browning of the shade ; and that acidity is correspondingly associated with a whiter colour. Now this alkalinity or acidity of the wool substance, producible at will, has no relation to the capacity to spin to fine counts, or to length of fibre, lustre, or even with soundness or good mechanical qualities. If the wool, alkaline from the scouring bowls, were acidified, its shade would be considerably improved, a species of pseudo bleach being produced ; but the subsequent stages of conversion into yarn could not be properly carried out on an acid and corrosive material. When sulphur bleached fabrics are to be put through the finishing operations, special attention has to be paid to the details of the plant, to prevent corrosion and staining of the goods. It therefore follows that mere whiteness cannot be taken as an absolute standard of judgment of wool tops, more especially as it cannot be decided with certainty that a given top has or has not passed through the backwashing process. Further, all the validity of this colour standard of wool quality is destroyed when tops are tinted. This is carried out by the addition of a suitable quantity of some very soluble and easily diffusible dyestuff such as Methyl Violet, to the backwashing liquor; the “blueing,’’ by complementary colour effect, partially annuls the natural creamy shade of the fibre or that part due to its alkaline state. This practice was forbidden during the War, but has suffered revival and is probably quite general. It will be admitted without question that Methyl Violet and Wool quality cannot be proportional ! N.B.—Tinting or blueing can often be detected by examina- tion in a good light, folding the material and looking into the crease; this shadow-light by multiple reflection appears to show up the superficial tinting component. Comparison of a strip of pure white, e.g., a bit of chemical filter-paper, is Usetul; - . I Quality and latent whiteness may thus be present even in a top of inferior shade. There are occasions when tops are given a peroxide bleach to secure the much-sought whiteness. It is very doubtful whether, when the material is afterwards oiled and scoured, this bleaching is at this stage of any value whatever, and undoubtedly the best bleaching results are achieved upon a clean fibre in the state of scoured cloth. In these days of strong peroxide bleaches, when quite low cross- breds are bleached up equal to Botany whites, the whole case

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for blueing or bleaching at the backwashing falls to the ground. In the case of tops destined for dyed piece goods, it is equally difficult to see the special significance attached to the factor of Whiteness in tops. At the best, the blueing up of tops is a temporary and evanescent affair, whose effects do not last as far as the cloth finisher, and the nature of the process itself precludes any permanency or even uniformity of effect.

It appears to be agreed among practical producers of yarns that backwashing prejudices the spin, perhaps due to dis- turbance by the scouring, or more by the special nature of the drying off, usually carried out on *‘ can driers.’”? Wool dried from the scouring bowls is certainly in superior condition to that of sliver subjected to the cylinder driers of the back- washing plant; this portion of the machine has been pro- gressively improved, as the defects of the older devices, baking and scorching, were experienced.

The backwashing plant is practically a two-bowl scouring set of diminished size, fitted with a drying system, usually consisting of heated cylinders, perforated and supplied with hot air in the later machines. As the dirt to be removed is not excessive, no drastic scouring is necessary, and it is quite as important to wash out all soap completely as it is to remove the primary dirt; residual soap becomes “ dirt.’’ Alkali is usually omitted and a plain soap scour applied. Probably a little weak alkali, 1-2°Tw., with an olein soap at a moderate temperature, 60—70°F. in the first bath is desirable. The second bath, which invariably acquires some detergent material from the first bowl, should be fed with a constant supply of warm soft water, and its overflow passed into the starting bow].

The Scouring of Yarn.

The scouring of wool in yarn form is required before certain dyeings or bleachings, and the remarkable extension of the hosiery trade has led to great developments in the methods applicable at this stage. Yarn is sometimes spun from raw wool, but usually the scouring at the yarn stage is intended to remove miscellaneous dirt and particularly oil from the combing and ‘spinning operations. The amount of such extraneous matter varies from 2% in worsted to over 20% on carpet yarns. The scouring may be preceded by a steaming of the stretched yarn. This is intended to produce a “ set,”’ and prevent curling during the scouring ; it is quite analogous to the preliminary crabbing or blowing of greasy pieces before scouring, and may, on certain machines, be carried out along with the scour.

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—THREE-BOWL YARN SCOURING MACHINE & McNaugut, Lrp., RocHDALe.)

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The appliances used in the scouring of yarns are usually adapted to the treatment of hanks :—

1. The hanks may be hung on sticks, suspended in the liquor, and frequently turned by hand.

2. The hanks are fed on to a travelling apron or lattice, and run backwards and forwards in tanks or bowls, having squeeze rollers as in wool scouring ; a succession of cleaner liquors and finally warm water is used. Earthenware rollers may be fitted to pass the hanks up and down in the trough.

3. In some machines used also for dyeing, the hanks are stretched with slight tension on rods carried in a frame; this frame is then rotated in and out of the scour.

4. Hanks made into a chain or rope are run many times through a bath and between squeeze rollers; then finally washed off.

The scouring of yarn is an ordinary emulsification of the dirt and spinning lubricant, and the general soap scour, made mildly alkaline, worked at a moderate temperature, is indicated. It is plainly necessary to guard against milling or felting.

The Scouring of Wool Piece Goods.

The details of a practical scouring scheme must necessarily vary with the nature of the goods being manufactured and the kind of finish necessitated thereby. Not only must the time of treatment, the active materials applied, the due regulation of heat, and a host of other factors be varied, but entire processes become essential or are wholly omitted as the case demands. In general, however, the major changes in the finish of cloths occur beyond the scouring stage; the milling operation, for example, broadly differentiates woollen and worsted fabrics, and the raising process is the means by which some of the most characteristic effects are obtained.

STANDARD SCOURING ROUTINES.

For scientific purposes, scouring methods may be classified according to their mode of action, as follows :—

1. SOLVENT SCOURING, in which oily and fatty matters

are extracted from the fibre by the direct solvent action of benzene, petrol, etc.

2. SAPONIFICATION SCOURING, in which the free fatty acid of the oils are converted into soaps in the scouring machine by the action of the alkali.

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3. EMULSIFICATION SCOURING, in which the greasy dirt is removed mechanically by the formation of a frothy lather or emulsion ; the wetting-out power of this latter causes the breaking up and detachment of the oil, etc., from the surface of the wool fibre. This is obviously a physical process as contrasted with the chemical process of scouring by saponification.

4. MECHANICAL SCOURING, e.g., by fuller’s earth.

Fie. 42.—ROPE OR DOLLY SCOURER.

(JAS. BAILEY, SLAITHWAITE, HUDDERSFIELD.)

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These are ideal types of scouring to which practical methods conform more or less. Thus, scouring of raw wool in the usual bowls is chiefly of the emulsification type; the scouring of fancy worsteds by weak alkali and some soap is a further example of emulsification working ; so also is the degumming of silk by a boiling soap bath. On the other hand, good woollens carrying oil with large percentages of free fatty acids may be scoured by alkali alone; sufficient soap is formed in the machine to use up the oil both directly as soap and in- directly as emulsion. This is a typical saponification scour. The scouring of low grade goods has usually to be of a com- posite kind.

The saponification scour is scientifically justifiable, is easy to carry out, and is thoroughly efficient. It is a standard scour on heavily oiled woollens. It is obvious that the oiling of wool for spinning and the subsequent scouring operations are intimately connected. In the case of good woollens it is assumed that the spinning oils are “* oleins,’’ with some mineral oil, say,-20%. In this case the oils will contain 20 to 75% of free fatty acids, and hence the scouring of such goods is quite practicable by alkali alone, as follows :—

Stage 1.—Run in soda-ash solution of 5°-6°Tw. at about using, say, 20 gallons per 100 Ibs. of wool. Let this saponify, running for 10 minutes or so, and then without. addition of water open the sud box and run the dirty emulsion away to the drain. When the machine is thus Stage 2.—Add alkali as before, about 5 gallons per 100 Ibs. of wool, scour for 20 minutes or so, and— Stage 3.—Wash first in warm water slowly, then more rapidly and colder.

The principles of this saponification two-stage scour are :—

1. Attack by alkali on the free fatty acids of the spinning lubricants with formation of soap. 2. The resulting emulsification detaches the superficial dirt of the fibre, and this is removed at an early stage from the machine. 3. This cleansing action is intensely assisted by the genera- tion in situ of carbonic acid gas by the action of the fatty acids on the alkali in forming soap; this is an extremely powerful detergent factor peculiar to saponi- fication as contrasted with purely emulsification scouring. 4. The use of a clean and unexhausted scour, of good diffusibility, for the removal of the dirt and oil which has penetrated more deeply into the fibre, and which requires longer continued action for its saponification

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and emulsification. It must be remembered that colloids do not diffuse through colloids ; soap as soap is not a penetrant of the wool fibre. But a crystalloid like soda carbonate possesses high diffusibility.

This method is probably the most efficient scour in point of cleanliness of the fabric. Seeing that much of the free fatty acid of the wool oil is oleic acid, the resulting soap formed in

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Fic. 43.—Back View, ROPE WASHER.

(Jas. BartEy, SLAITHWAITE, HUDDERSFIELD.)

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the machine is sodium oleate, which is soluble at comparatively low temperatures.

In the scouring of high-class worsteds, the oiling is much less in quantity and is usually of a more neutral character. The saponification of a neutral oil—even when of animal or vegetable origin—cannot be effected by carbonated alkalis at ordinary scouring temperatures. Hence a _ straightforward saponification scour is not feasible on these goods, and the usual process is as follows :—

FANCY WORSTEDS SCOUR.—Alkali of 2°-4°Tw., together with some soap is used from the outset, the idea being to work up an emulsion which, by diminished surface tension or in- creased wetting-out capacity, will detach the oil and dirt and float them away from the fabric.

It would be interesting to know the practical reasons, if any exist, why worsted spinners do not use oils with large fatty acid content. The addition of small amounts of free fatty acid to mineral oil for machine lubricants has been found to increase their efficiency, diminishing the friction in some cases to one-half that of mineral oil alone. In the textile case, the presence of free fatty acids enormously facilitates the work of the scourer. As an actual fact, many worsted “ oleines’”’ contain moderate percentages of fatty acids. In these cases it. is possible—and often superior practice—to conduct a worsted scour thus :—

1. Run in alkali 2°-4°Tw., warm for 10 minutes, and then, without any addition of water, lead the sud off to the drain.

2. Add more alkali—preferably weaker—and some soap, and complete the scour.

3. Wash off, warm and gently at first, colder later.

Over-strong alkali solutions prevent the proper solution of the soap; it is far preferable to work with weaker solutions and in more than one stage.

THE *“ LOW GOODS ” SCOUR.—In this class of trade the scourer meets with his worst difficulties. There may be excessive bleeding of colour due to loose dyeings, poor dyestuffs, dyeing in the grease, low grade oilings, often with much mineral oil; sizings ; recovered wools, flock, and the rest. In many cases the conditions to be met are in- compatible, e.g., the necessity of scouring at low temperatures. to prevent bleeding, thus losing the advantage of the decreased. surface tension (i.e., enhanced wetting-out power) of a warm scour.

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The low grade oilings in these goods offer the maximum of difficulty. There is often much mineral oil, which tends to prevent the formation of proper emulsions, and being itself unsaponifiable; is removable only by a process of emulsification.

r= ie) iE aoe ne

Fic. 44.—Sripe Evevation, DOLLY SCOURER. (Jas. BatLEy, SLAITHWAITE, HUDDERSFIELD.)

There is usually an undue proportion of other unsaponifiable matter and a corresponding lack of free fatty acids; a sufficiency of these would in many cases simplify the scouring of the goods, enabling, at any rate, the first stage of a saponi- fication scour to be effected. Many so-called * black oils ”’

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are excellent from the scourer’s point of view, owing to their high content of free fatty acids ; much of the scouring of low grade goods would be vastly improved by a judicious addition of suitable black oil to the spinning lubricant. It is un- doubtedly desirable that wool oils should be specified in terms of free fatty acid, in addition to—or in place of —total saponi- fiable matter.

It is therefore not possible to lay down the exact lines of a low goods scouring operation. If the oiling can be modified in the direction of securing a proper quantum of free fatty acids, then a two-stage scour of the following type may be practised :—

1. Run in alkali 5°-6°Tw. warm if the colours do not bleed ; otherwise, cold. Scour for 10-15 minutes and, without added water, open the sud box and run this away to the drain. I 2. Add further alkali, weakened, together with some soap, to build up an emulsion ; scour out. 3. Wash down, preferably with warm water at first, if the dyeings will permit. There are some special points in the practice of low goods scouring which merit further discussion.

In some cases slight additions of caustic soda to the first stage of the scour may be found useful. Caustic as against carbonated alkali will saponify free fatty acid in the cold ; it is further more active in the softening of possible hardness in the water. But the concentration of such caustic alkali must be small in view of its strong tendering action on the wool fibre ; a strength of perhaps not more than 2 ozs. in 10 gallons of the scour may be tried. Further experiments are necessary.

Another question bearing on the low grade scour more particularly, is the use of the so-called “ solvents.”’ Only a few, viz., alcohol, carbon tetrachloride, tetrachlorethane, etc., are adapted for employment as adjuncts to a textile scour ; and their true utility is not the dissolving of oil or grease, but their property of lowering the surface tension of the scour, in which they act more efficiently than soap. Hence there is scientific justification for their use under proper conditions, but further experience is necessary to determine which sub- stance, and under what conditions, the highest efficiency is obtained. The whole question is one requiring further investigation. Some useful notions respecting the principles of scouring and the proper modes of procedure may be gained by con- sidering certain extreme cases not necessarily met with in practice :—

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Suppose fabrics were “ oiled ” as follows : 1. Oiled with pure mineral only. 2. Oiled with pure neutral animal or vegetable oil only. 3. Oiled with pure free fatty acids only. 4. Lubricated with dilute glycerine. Taking the last case first, a simple steeping and working in warm water would cleanse the fabric. The cloth oiled by free fatty acid could be completely scoured by the use of alkali alone. The fabrics having either mineral oil or neutral glycerides would require soapy emulsions, perhaps repeated several times, or, alternatively, extraction by solvents.

Fic. 45.—DOUBLE MANGLE For PIECES.

(Jas. BatLEy, SLAITHWAITE, HUDDERSFIELD.)

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Preparatory Operations to Scouring of Pieces.

The pieces as received by the finisher from the weaving shed may, in the case of some worsted fabrics, have a general resemblance to its final condition as delivered on the counter of the merchant’s warehouse. In other cases, as in woollens. it can hardly be identified as the same fabric, even in embryo, In general, unfinished cloths are “‘thready’’ and of harsh handle ; they show all kinds of defects, e.g., knots, loose ends, slubs, holes, floats, breakages of weave, ete. Along with these is the presence of actual impurities. Finally, the special finishing effects characteristic of the fabrics as worn are undeveloped. As the efficient scouring of cloths is a funda-

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Fie. 46.—POWER PERCH WITH MEASURiNG, OPENING, AND MoTIONs.

(SELLERS & Co., )

mental process in the finishing routine, it is desirable to consider the related operations. There are certain preliminary details which have attention on the ‘“‘ grey ’’—that is, the undyed or greasy pieces, as received from the loom—such as Burling, Knotting, Mending, Perching, Numbering, Measuring and weighing and entering in the “‘ grey piece ’’ book, hand- perching for loom stains, etc. For a commission finisher to _ begin work on pieces without first perching is extremely unwise, as it is in his own interest to safeguard himself against damages in the finished goods, in which state it is often difficult to determine the responsibility as between maker and finisher. PERCHING consists in the thorough examination of the cloth when drawn over a pole or roller—the perch—in a good

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light, preferably a window with a north aspect, the object being the detection of all faults and defects so as to remedy them at the mending table or elsewhere. Many cloths are perched through, i.e., the percher’s assistant stands between two vertical lengths of the fabric, inspecting it for holes, thin places, certain stains, etc., by the aid of the transmitted light. Obviously very thick double or backed cloths are not suitable for this method of examination. In general, both face and back of the cloth are inspected. The of a cloth is usually the upper surface as the piece is woven in the loom and the external surface in the made-up garment. It is generally smarter and cleaner, even in the unfinished piece, and has fewer projecting fibres, etc., than the back. If the weave of the cloth shows diagonal lines, ** twills,’’ as in serges, etc., these as a rule run upwards from left to right on the face of the pattern. The face of the cloth is often distinguished by having a short length of yarn stitched in at the end, so as to show most of its length on the face side. This is the “* Face Mark ”’ or *“‘ Shuttle Pick,’ the weaver threading in a number of differently coloured threads about six inches long so as to show long floats on the face and little on the back. For dyed goods, light blue (indigo) cotton, which does not take the wool dye, is used. It is usual for the numbering to be done at the head end of the face side, but this is not invariable, some firms numbering on the back. In default of a shuttle pick, the numbering is a guide to the face side, but in such a case the finisher could hardly be blamed if the piece got finished ‘back up.’ In all equal weaves, plain or canvas, hopsack, Celtic or regular herring-bone twills, where the warp is all one colour, either side could be made into the face, but in the great majority of patterns it is fairly obvious by the smarter appear- ance and nicer design (particularly in fancies), which is the face side and which should therefore have the superior finish. In warp and weft backed cloths the face is generally obvious from the back weave being looser, owing to the longer floats in the back warp and weft.

HEAD AND TAIL ENDS.

It is usual for the weaver to commence with a tail end and finish the piece with a head end. This is not universal, however, as different firms and even different weavers at the same firm do the opposite. _Again, in three or four “ cut ” warps, many weavers make two headings together at the end of the first and the beginning of the second pieces, then two tails together when ‘“‘ middling ”’ the second cut. This causes the second piece to be finished the opposite way to the first, so that a damage in the warp running through both would therefore be on opposite sides of the two pieces.

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_ The repeat of the weft bobbins will vary according to the weight of yarn on the bobbin and the counts of the yarn, that is on the fineness of the counts and the number of picks per inch. In the Bradford trade, for example, white worsteds are woven on “ plain’ looms, single shuttle, and a bobbin may weave 4-8 inches of cloth. If the work is well done, it is very difficult to tell where the bobbins are changed, although there are bound to be the broken threads at the lists. Some weavers break these off carelessly, causing the last pick to be pulled very tight. Again, if the shuttle spindle is not true— either bent or worn slack—it will cause friction in the thread leaving the shuttle, which increases‘as the bobbin empties, thereby tightening the weft and narrowing the piece.

DEFECTS AT THE PERCH.

Generally speaking, any defect which occurs at regular intervals in the piece or in a regular sequence, is due to a mechanical cause. Again, any mark in the piece which runs absolutely straight, i.e., with the threads either warp way or weft way, is a manufacturing damage, as it is almost impossible for it to be caused in the finishing processes. 1. Ends or picks missing. 2. Trailers-in, intakes or runners during weaving; extra portions of yarn dragged in near the list. Where there are two or more shuttles and the pick in going through the shed catches the stationary thread and draws it forward into the shed, this causes a double portion of wrong weft to be “ trailed in ”’ at the lists. 3. Temple marks; caused by bad rings, worn or bent points, which may cut the weft or pull it into loops or staples. 4, Tight, jammed, slack, thin (or hollow) places; due to uneven weft or uneven letting-off of the warp beam or uneven taking up of the cloth beam. 5. Warp defects due to bent reeds or harness ; causing the warp threads to be unevenly distributed. In some goods remedied in finishing. 6. Bad places caused through flying shuttle and “ traps ”’ heald traps or weft floats through the a running down and holding the shed. 7. Streaks due to dirty carding, neglected “ fettling ”’ (cleaning) ; allowing the cards to get too full of shoddy. 8. Weft bars due to uneven or mixed yarn. 9. Loom stains ; generally near the middle or at selfedges, caused by careless oiling of the weft forks or the temples. 10. Coloured ends wrongly replaced or working wrongly from the design or plan.

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11. Mistakes in draft or lags on loom; these should have been corrected in the * passing bit.”’ ; 12. Cracked places; the irregular working of the let-off or take-up motion of the loom, generally at regular: intervals, varying with the diameter of the warp on the beam, or irregular working of the *‘ ratchets.”’ 13. Ends over or under picked. 14. Small holes. 15. Pulled threads due to “ gratter ’’ on loom ; or staples. 16. Tight picks. 17. Stains ; in commission work, * maker’s strings.”’

Knotting, The knots in the grey piece are due to breakages in the threads and tying in either in the spinning, winding, warping or weaving processes. They are found by the methods of eye examination and hand feeling, and in clear finished goods are pulled through the piece to the back for cutting off; the first passage through the cropping machine cuts the back before the face, or in multiple cutters, the first blade operates on the back. In this stage, also, slubs, i.e., thick places in the yarn, are thinned down or removed by the use of burling-irons or scissors. Clear surface goods may have the knots left to the cutting stage to allow for shrinkage. Pressed face goods have the knots drawn to the back and removed after scouring. Flannels and vicunas have the knots drawn to the back and removed before scouring. The guiding principle in these matters is that the knots must not be felted in during the scouring or milling. Clear cut piece goods, coarse and medium counts, have the knots drawn to the back and removed before cutting. Colour and weave effects (worsteds); the knots are passed to the back and removed before cutting. Saxonies, semi or covered finish, the knots are cleared before the wet processes. Cheviots, according to finish, fairly clean and loosely set ; the knots are removed after the wet processes if there is a contrast in the warp and weft. If there is fair or much cover or dark shades, the knots are removed before the wet processes. In blankets, moss finish, and velours, the knotting is before scouring, milling, or raising. In some goods it is necessary to unfasten the knots and leave the loose ends until after scouring, or in very open weave serges (thick counts), to stitch the ends in according to the weave.

Mending (or Darning).

This department is an index of the efficiency of the weaving shed. It consists in the repairing of faulty places in the texture by actual hand work, i.e., a species of darning. These places are usually marked by the percher with chalk. The

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kinds of defects and inequalities dealt with by the mending staff include the following :—

1. Short ends and picks. 2. Picks missing. 3. Jack missings ; improper interlacings of threads, due to wrong working of jacks on the loom. 4. Tight picks ; over tension on weft during weaving. 5. Skimmed picks, floating picks, portions of weft not interlacing at all. 6. Long ends missing ; lengths of warp missing. 7. Ends working wrongly ; ; due to replacing broken ends through wrong gates or broken gates. 8. Weaver's traps, difficult for a mender to deal with

satisfactorily. 9. Different sized threads ; different counts wrongly used, or twofold in place of single yarn or tightly twisted threads. These must be replaced by correct yarns. 10. Slacks or loops (staples). In some goods occur during the weaving; may be drawn up and passed to the back or cut off before or after scouring, according to finish. 11. Holes. Mending is obviously simpler in plain as against fancy goods, also in loosely woven fabrics of coarse counts versus tightly set cloths of fine counts. It is not always possible, because of the tightness or fineness to mend cloths in the grease. Some woollens, which shrink considerably in the scouring, are better mended after scouring and milling. Some dress faced cloths, e.g., Beavers, are mended both before and after scouring, i.e., previous to milling. Portions of similar yarns are inserted according to the weave, the loose ends being drawn to the back of the goods and either then cut off short or short tails left for skrinkage. After the removal of ** slubs,’’ the threads surrounding these patches are preened ”’ into place.

CLASSIFICATION OF GOODS FOR MENDING.

1. Colour and weave effects, clear or semi-covered finish. These require every attention from the mender. 2. Plain clear cut cloths, piece-dyed or self-coloured. The mending varies, in the coarse counts they should all be mended. On cloths which are well set and of fine counts, short single ends and picks may be often omitted, the weave having an influence in this respect. Thus in a 3/3 twill the threads are not so prominent as in a 2/2 twill, where a clean cut is produced in the weave by a breakage. 3. Fancies for clear finish, where colour or fancy weaves are used. Coloured threads are always mended and generally other defects.

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4, Dark shades, as Oxford greys or similar dark mixtures ; clear or covered worsteds or woollens. It is less necessary to mend these thoroughly, the shade tending to obscure the inequalities. 5. Vicunas, flannels or similar goods. Knotting is usually sufficient, only the worst defects being mended. 6. Cloths for raised finish, blankets, moss and velour finish. As vicunas, above, except that ends out, causing weft floats, must be mended, or will show stripes when mended. 7. Dress faced goods. These must be well mended to secure perfect fabrics. In doeskins, single ends are left unmended. 8. Compound structures of all above classes. In lined cloths equal attention is given to the back and face, but in many cloths only the serious backing defects are mended.

WEAVES AND MENDING.

Plain weave goods are all mended. In regular twills, the 2/2 are all mended in clear cut goods; the 3/3 and 4/4 are more frequently overlooked; fineness and closeness are helpful. In whipcords, the short single ends may be safely omitted and sometimes single picks. In Barathea and many spot weaves, single ends are not always mended, preference being always given to fine yarns and close settings.

Numbering.

Pieces are usually given a series number and other par- ticulars, e.g., width for finishing, etc., may be put on the cloth. This is often done by the sewing machine, but an alternative system is to attach a tag of calico, padded in aniline salt, and use a developing solution on rubber stamps. The developer is a weak solution of permanganate, bichrome, and a little vitriol. The piece book in the grey warehouse should contain particulars of the grey weight, length, and width. A general piece book might be arranged as follows :—

PIECE BOOK. Finisher’s I 1, 2, 3, 4, 5, 6, 7, 8, 9, Grey I Grey Piece No. I for Scouring, Tenter, I Weight. Length, _ Cutting, Blowing, I I I Pressing, etc. I Grey Width. ‘Finisher’s Weight I Width. I Length. I Strings. |Date delivered.

The various particulars being entered in convenient columns.

The Crabbing Process.

The operation of crabbing is intended to give to piece goods the characters of “permanent set’’ with the intention of preventing distortions in subsequent processes. It therefore makes use jointly of the effects of heat and moisture upon the

Date. I Order No.

I

I I I I

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wool tissue, but in the exact details of their application there is great variation. A.typical crabbing includes treatment both by hot water and by steam applied to the fabric while wound in roll form, but the term is often restricted to the former only. Where is the crabbing process necessary or desirable? As its primary function is to eliminate or prevent distortion, it is required wherever the structure of the cloth, the nature of the wool, the presence of latent strains, or the needed fixation against later treatments come into question. Reference to

Fie. 51.—SIMPLE CRABBER.

the chapter on the Physical Properties of Wool and to the table of fibre lengths and qualities, will show what possi- bilities of uneven shrinkage may occur in certain fabrics. Union dress cloths (cotton and wool), Glorias (silk and wool), and cloths of mixed fibres, generally may require crabbing ; also, if of widely differing qualities of the same fibre, hard and soft. Cloths with very tight spin or tight setting have hidden strains which cause crimping and cockling in the scouring, unless previously released and set. A typical case of mixed fibre quality occurs in the cloths called “* wool backs,”’ having a thin worsted face overlying a thick wool, often shoddy, back ; a preliminary crabbing is required to prevent streakiness. Some worsteds have a Botany warp and Crossbred weft, a combination likely to yield a crapy effect if not well set from the beginning. Another case of interest in this connection is that of lustre dress fabrics—cotton warp and thick mohair

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weft—in the grey state the dull cotton shows prominently. In crabbing, the cotton warp is pulled straighter, the lustrous mohair weft comes to the surface, giving the cloth its requisite finish. One of the most frequent applications of crabbing is in worsted cloths made of crossbred wools of the lower qualities, which combine great tensile strength with a high degree of toughness and harshness of handle. Such fabrics are un- workable in the finishing processes unless given an enduring Moreover, the beauty of the final finish is greatly enhanced, the regularity and parallelism of the twills of serges, etc., being very marked. In some cases these cloths are double blown—that is, once head end first and next tail end first— but this is not quite so effective as crabbing, though it is less dangerous. Cloths, of this kind, in the lower qualities, are often dyed unscoured from the crabbing, the so-called ‘* Leeds In some other instances, a complicated weave, or interlacings of warp and weft, render it desirable to crab the fabric, e.g., hopsacks, corkscrews, gabardines, etc. Crabbing machines may be arranged in various ways, but the essential elements are as follows :— 1. A roller, often perforated, generally of copper, running in a trough. Circulation of warm or cold water from the roller through the roll of cloth to the trough, or vice versa. 2. Perforated rollers at the front and back of the machine, for blowing pieces with steam. 3. Twitch rails and drag rollers and rails for supplying the necessary tension and even feed. 4. Gearing with clutches and brakes, to run and reverse the rolls. 5. Steam and water connections. One of the greatest dangers of crabbing is the production and fixation of stains, not only because it is carried out on the dirty and unscoured cloth, but also because of the nature of the machine with steam, water, and oil, and the brass, copper and iron surfaces and moving parts. A great gain in cleanli- ness results from the use of aluminium rollers, an improvement made by the author many years ago. In addition, the steam rollers should be fitted at each perforation with the self-draining nipples, to prevent condensed water being forced into the cloth roll, with consequent water-marking, which are usually rust and dirt marks as well. The crabbing trough may be also made of aluminium.

ROUTINE OF CRABBING.

A couple of ten-yard lengths of cotton wrapper will be needed for each roll. One of these is wrapped round the roll

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previous to winding on, for the purpose of preventing contact with the metal of the roll and securing an even distribution of water or steam ; the other length forms the external closing and binding envelope for the piece. If the wrapper is too short, each perforation will be reproduced on the cloth. The pieces

Fic. 52.—TWO-BOWL CRABBING MACHINE. (SELLERS & Co., HUDDERSFIELD.)

to be crabbed are first cuttled out straight on scrays in front of the machine, the end passed through the twitch rails, which are adjusted to give sufficient tension, and on to one of the side rolls by two operatives standing at each list ; these guide the piece, pulling it out weft ways, so as to secure perfectly parallel edges in the roll. From this the cloth, now evenly

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rolled, may be run to the crabbing roller in an even and uniform manner, the tension being adjusted by the brake drum on the side roller ; meanwhile, the trough has hot water at the correct temperature and at a sufficient level to secure a proper wetting and penetration of the fabric. In some cases the cloth is run direct from the cuttles to the crabbing roller. In others, a winding-on machine, a combination of a short length of tenter chain and rolls, is employed. While on the main crabbing roller, hotwater may be forced through the piece by a circulating pump drawing from the trough, or oppositely from the trough through the piece to the roller and pump, etc. The temp- erature should depend on the kind of work done, but 140—180°F. are practical limits. Some crabbers make additions of weak alkali and soap to the water, and there is possible utility in this ; it will favour quick wetting-out and tend to prevent the setting of dirt in the cloth. The next stage is the unwinding of the cloth from the crabbing roller on to one of the steaming rollers. Steam is blown through the cloth until it is freed from the dripping water and is steam dry; this may take 10-15 minutes, and with very thick or long cloths a reversed blowing may be necessary. Cold air is now pumped through from the atmosphere by an air-pump, of the piston or Root’s type, and the piece unwound and laid out in even cuttles to cool down completely. In all cases the most thorough job is obtained by doubling each stage, running the cloth on in the reverse way; this is to correct the inevitable inequalities of treatment which must occur between the inside and outside of a rolled fabric. The underlying principle of the crabbing process will be obvious from the description of the effects of heat and moisture upon wool substance in Chapter X. The effect of the hot water and the subsequent steaming is to put the wool into the plastic state. In the act of rolling, the piece is in longi- tudinal tension, the warp yarns, of course, carrying the stress. When the heat and moisture have removed the initial rigidity of the wool, this stress is automatically relaxed, all latent strains of spinning and weaving are released, the intersections of the warp and weft take up their proper geometrical relation- ships, and the fabric becomes a balanced structure, which is permanently set at the cooling stage. There is usually con- siderable shrinkage in width in the crabbing process, 1-2 or even 3 inches on the broad width often resulting. This is sometimes checked by winding the cloth to the roll from a short length of tenter chain, where an initial lateral stretch may be given. Crabbing, honestly and skilfully carried out, yields on the proper fabrics a finish unattainable by any other means, but it is full of dangers. The question of tension in the winding of the roll is of primary importance, and eannot

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be judged except by experience and observation. It is easy to see that a slackly wound cloth will become baggy and cockled on the rolls and will show unevenness on winding off ; it will also be raw in appearance and will not have acquired the necessary set. Excess of tension is rather more complicated, It is a well known practical point, and can be mathematically -deduced, that the winding of a roll under tension produces in each layer a pressure on subjacent layers, and that this pressure increases with the number of layers in the roll. If the tension

Bia. 53:

REFITT’S STEAMING-OFF MACHINE. (SELLERS & Co., HUDDERSFIELD.) Arranged for continuous working : five pieces in process simultaneously.

is excessive, the pressure in the inmost layers may be so great as—when the wool has come to the plastic state—to emboss or print the weave or design on the adjacent layer of cloth. Such printings are quite common and are wrongly termed ““water marks’’; they are properly pressure marks. True water marks come from condensed steam blown out of the roller into the cloth and are invariably accompanied by staining. Pressure marks may sometimes be removed by reversing the ends and reblowing, or by crabbing at a higher temperature. Uneven flow of the crabbing liquor or the steam causes differences in the “‘ set’? at various parts of the piece ; if the flow or escape is not fairly equal at both ends of the roll, one side may show “ listed’? when dyed up. Very dirty pieces are troublesome in crabbing, as the water and steam tend to

Q

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drive the dirt in front of the current, and curious “ barry ”’ effects sometimes result from this cause. If pieces have been treated in the grey state with preparations to remove stains, or if they show bad patches of loom grease, etc., such areas almost invariably get worse by crabbing, which often appears to actually facilitate the penetration of dirt into the wool tissue itself. The lustre of a cloth is much improved by the crabbing operation, an obvious consequence of the increased regularity of the elements of the cloth structure. It is much simpler and obviates many troubles to crab with the aid of a wrapper wound on fold and fold with the piece; but it is plainly expensive, as the routine is drastic and the life of the wrappers comparatively short ; also, they tend to collect dirt and must be frequently scoured. Immediately any tearing or other faults develop in them, they must be discarded for fear of printing defects. Crabbing stains usually dye up darker than the rest of the cloth. Creases may be formed by the roller wrapper if not well smoothed down; these are revealed by their occurrence at intervals corresponding to the roller circumference and by their becoming fainter and fainter on the different layers, until they die out. Creasing may also occur at the cuttles, if wound off too hot. In severe cases of printing or creasing, the pieces may have to be slightly milled. It must be noted that the whole operation of crabbing has a weakening effect on the yarns. Piece-dyed goods are sometimes crabbed to improve the lustre and give a solid handle, but the dyestuffs must be carefully chosen, as otherwise both bleeding and alteration of shade may occur. Negligent winding on is apt to cause the selvedges to be up,” i.e., present a waved or corrugated appearance, generally down one side of the piece. If the steaming is overdone, the piece becomes “‘ steam-blown,”’ and this portion in dyeing behaves like a resist. Conditioning faults in yarn are very liable to be developed in the crabbing process, evidently because there are differences of absorptive power in the various parts. I

NOTE ON ROLL WINDING.

As there are many instances in textile work where material is wound into rolls, it is interesting to examine the mechanical results. An elementary mathematical investigation leads to the conclusion that the internal pressure developed varies directly with the number of turns, and inversely with the radius of the layer; this, with a constant winding tension. In this, the effect of elasticity is neglected and also that of friction. The actual internal pressures are considerably less than other- wise on these accounts. Compare, for example, the effect obtained when large guns are wound with many layers of steel wire. .

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Discussion of Scouring Principles.

Most of the machine details will be separately considered in the chapter on Machine Design and Lay-out of Plant, Chapter XIII; the present discussion applies directly to the Rope or Dolly Scourer, and also with little modification to Open-width

FRONT VIEW.

Back VIEw.

Fic. 54.—Cross-DRAFTING IN THE ROPE SCOURER.

Scourers and combined scouring and milling machines. The pieces are entered into the machine dry ; the use of the soaper, wetting-out machine, or “lecker,’’ should be exceptional, a. general law of the scouring shed being that pieces must lie in the wet state as little as possible to avoid mildews, stains,

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Fie. 55.—PIECE END SEWING MACHINE. BrrcoH, SALFORD, MANCHESTER.)

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bleeding of dyeings, etc. As a rule, cross drafting of the pieces in the scouring machine is a good practice; it is usually sufficient to cross-draft in pairs :—Thus if the two pieces are denoted by the lines A B C D I then, the pieces being crossed on one side of the rollers, the end B is sewn to C and D to A, thus ensuring the pieces running in non-parallel tracks, and tending to avoid rigs; they encounter different parts of the rollers, producing uniformity of treatment. It is necessary in cross-drafting that the rollers. should be even and in good condition, as indeed should be the case also for perfect wringing out of the scour, and the avoid- ance of stains from decaying wood. If the rollers are worn unevenly at different parts, the peripheral speeds at these parts vary, and therefore the speeds of travel of the cloth ; hence one part of a draft may tighten up. The machine must then be stopped and the slack pulled in. Cross-drafting of three pieces may be practised, but the possibility of tightening up is increased. Obviously the device is applicable to milling also. The pieces having been passed into the machine and stitched into endless bands, the run is ready ; the question of the particular scouring detergents to be used and their amounts now arises. Some outline of the principles underlying the choice of a scouring medium has already been given in treating of fatty acids, of proper strength of alkali, etc. In the main, there will be distinct systems of scouring corresponding to the heavy and light oiling on the goods in the yarn stage ; and this, broadly speaking, is defined by the dividing line between woollen and worsted. The heavy oiling of the former goods requires a scour chiefly based on alkali for the preliminary saponification of the free fatty acids of the spinning oils. The comparatively light lubrication of the latter indicates a combined alkali-soap scour aimed more at general emulsification from the start. No sharp line of demarcation is possible, but the heavily oiled woollens are best scoured in stages, whereas the cleaner worsteds may usually be carried through in one operation. The best strengths of both soap and alkali for the scour have already received theoretical consideration, and it may be assumed that a thorough wetting-out of the cloth needs some- thing like 2, 3, or even 4 times the dry weight of the piece ; say 15-30 gallons per 100 lbs. cloth. Many scourers have a tendency to run their pieces with too little liquor in the machine ; it is true that undue thinness of the scour is detri- mental to the proper formation of the emulsion, but a real wetting of the piece is necessary for the penetration of me fibre substance.

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246 WHEN IS A SCOURED FABRIC CLEAN ?

The average scourer is accustomed .to test his pieces for cleanliness by allowing the edge of the piece to run through his fingers ; there is a peculiar slip or greasy feeling about a piece not thoroughly clean, quite recognisable by those with practical experience. There is also the appearance of the cloth as regards eye observations when a handful is wrung out; if it is a black-and-white, there is the contrast of the check or twill, etc. An even better test is to take a pint pot, preferably white, and draw a sample of the effluent from the shuttle as it leaves the machine. This may give several indications :— _ 1. There may be a grease or soap film on the surface ; in this case, continue the scouring. 2. Colour may be coming away freely ; see that the wash- 7 water is not too hot. Of course, colour bleeding may be the fault of the dyeing department, or the use of inferior dyestuffs. 3. When tasted, there may be slight traces of soap or alkali still washing away. As in (1) above, run a little longer.

Theoretically, a Soxhlet extraction of a portion of the fabric would be required to determine whether all traces of lubricant had been removed in the scour, and the question of residual soap or grease naturally arises at this juncture.

Prof. J. W. McBain remarks (Third Report on Colloid Chemistry, p. 26) :— I ‘““As a matter of fact, it is often extremely difficult to remove soap from a fabric after the operation of washing.”’ Numerous special adaptations of plant and modifications of operations are made for the scouring of particular fabrics. Thus plushes are washed upon a winch machine, the goods simply passing over a skeleton roller to secure the necessary movement of cloth and liquor. Some of the attention paid to heavy squeezing in rope scouring could be diverted to the detergent medium with much advantage in other branches of the trade. In the scouring of Curls, Olympians, Marlboroughs, etc., practice has shown that the best results are obtained by a preliminary running of the pieces through the “ lecker ” in a solution of about 6°Tw., cuttling them out and allowing them to stand aside from 4-6 hours. This gives the curl time to commence before the actual scouring, and secures an even permeation and wetting-out ; in the scouring the curl forms much more evenly. They should be turned frequently, say every five minutes, first on the face and then on the back, during the run. I A useful detail in the scouring shed is a hose-pipe—ordinary canvas rubber garden hose—permanently attached to the

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water supply, for washing away clots of lather from the sides of the machine, the draftboard, the ends of the rollers, etc. Before the pieces are removed from the machine, all the dirt should have passed away to the drain and perfectly clean have run for some little time. Anything falling on the piece after the washing-off process means unlevel dyeing or bleaching, stains, or local differences of finish. Goods of

Fig. 56.—ELECTRIC DRIVEN PIECE WINCH VAT.

(JAS. BAILEY, SLAITHWAITE, HUDDERSFIELD.)

superior quality are best handled in clean cotton wrappers, at least until tentered. This brings up the question of machine cleaning in general.

The design of scouring and milling plant in order to secure cleanliness receives consideration in Chapter XIII; but the

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ordinary operations of the scouring and milling department should include regular cleaning down. It is not uncommon to find a scouring machine normally carrying two or three buckets of sludge, composed of wool-flock, soap residues, grease, iron- rust, in short, a complex mixture of all the forms of textile dirt and filth. The view apparently holds that this is of a permanent character and undisturbed by the successive scouring operations ; and is therefore harmless and negligible. Hardly a moment’s thought is necessary to realise the fallacy of this notion. The material in question is the result of former scouring operations ; each scour brings its quota and— also removes a portion. Quite commonly it is removed from the machine by being deposited on the cloth as a stain. No

Fig. 57.—THeE Rope Scourer.

accumulation of clots of dirty, greasy, and soapy flock should be permitted, all ledges and crevices being regularly examined. The ends of the rollers should be cleaned by a long-handled scrubbing brush and hot alkali ; actual fungoid growths some- times occur in these places. It must not be overlooked that the end grain of wood is peculiarly liable to early decay. No purity of shades, no lustre, no high finishes are possible with machines operated under dirty conditions. In milling in the grease, it is quite usual to find the interior of the machine

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thickly crusted over by a deposit of alkali and partially saponified grease with abundant flock ; pieces of which must infallibly be frequently detached upon the fabric. In the conditions under which this process is quite usually practised, it would be more fitly described as *‘ milling the grease in.” It is known that the method does not produce so close and good a felting as the milling of properly cleaned goods. Every holiday stoppage, the iron-work of the scouring and milling plant should be painted, preferably by a medium having a non-metallic base, e.g., a tar or bitumen preparation. The woodwork cannot be painted internally, and hence it need not be painted externally, as there is probably no gain in working life thereby ; rotting takes place from the inside. But the outside must be kept clean. The maintenance of rollers has already been touched upon; good scouring cannot be performed with uneven, knotted, cracked, or decaying rollers. Holes and cracks are apt to absorb dirty scouring liquors and pump them out again during running, accompanied by decaying wood, the result being a crop of stains or cloudy dyeings. Special scouring machines should be reserved for burl dyeing, staining of cotton warps, shower-proofing, etc. ; trouble may ensue if the ordinary scouring operations follow these without a thorough wash-down. There is a psychological factor in a cleanly environment, which is not without its: effect on the staff of the department.

COLOUR-BLEEDING.

This is a common trouble in the scouring, and is mainly a question for the dyer either of faulty operation or inferior dyestuffs. The use of overheated water or excessive alkali- strengths by the scourer may cause this defect even on properly dyed materials. Acid colours and cotton colours are par- ticularly prone to bleeding. In the fancy mantle trade it has been found an advantage to use of common salt in the scour of 6°Tw. alkali; without prejudicing the scour very greatly, this prevents the loss of colour. Glauber’s salt (sodium sulphate) is used for the same purpose, but excess must be avoided, or the soap may be salted out and the formation of an emulsion rendered impossible. The “ smutting-off ’’ of colour on dried-off fabrics is due to a number of causes; hard waters depositing mineral matter, the setting back of dirt owing to faulty dilution of the scouring emulsion, unsaponifiable matter in spinning oils, badly washed wool, and generally to dirt not removed from the fibre. Badly cleansed wool means loose dyeings ; the fabric in the scour then loses colour continuously ; even when the waste waters flow cleaner, a little squeezing in the hand brings away further colour.

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Actual tearing of the cloth in the scour may occur if the rollers, draftboard, etc., are damaged by decay or splintered. Over-carbonised cloth is tendered and easily torn. Wrapping round the rollers may cause tearing ; this is due to running over-dry, or over-crowding of the machine ; also to want of tension from the dicky roller at the front of the machine. This should be placed high up, and may have a ribbed or corrugated surface. I In some worsted fabrics containing effect threads of silk, etc., with delicate colours, the scour is by fuller’s earth, with or without alkali. Pieces in which stripes or coloured lists have bled may sometimes be cleared by a weak soap scour and ammonia as the alkali. Basic dyes are apt to rub if the scouring takes place with hard waters. On wool, the Acid Alizarine dyes and the After Chrome dyestuffs are generally fast, and in cotton the vat dyes of the Anthraquinone and Indigoid types.

MECHANICAL ACTION IN SCOURING.

The merely mechanical actions occurring in the scouring machine are of two kinds :— 1. Pressure; of the rollers upon the fabric, expelling the scour already applied and allowing new and more effective liquor to attack the dirty surface, and also by penetration, swelling the fibre and diffusing out the absorbed oil, dirt, ete. 2. Agitation; which establishes the emulsion by the formation of small globules, entanglement of air, production of colloid films with high absorptive powers, etc. It must be noted that mere shaking is at best an incomplete method of making emulsions. As the emulsion becomes more perfect—i.e., as its particles become finer—the disintegration becomes feebler ; the smashing action of the mechanical forces on the light particles is relatively less. A different factor, and probably a powerful one, is the liberation of carbon dioxide gas in the saponification of free fatty acid by sodium carbonate in scouring by alkali. The powerful effect of this agitation factor is seen in some experiments by Briggs (Jour. Phys. Chem., 1920). Using a mechanical shaker giving 400 shakes per minute and 1% solution of sodium oleate, 80% by volume of benzene could be emulsified in fifteen minutes ; it took, however, two hours to emulsify 96% of benzene, and 99% of benzene was not completely emulsified after eight hours of continuous shaking. The result shows the importance of working in more than one stage if very large quantities of dirt are to be emulsified out of a cloth into a scour. If the shaking was done intermittently

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25]

by hand, so that the emulsified benzene could separate out at intervals, the number of shakes was reduced enormously :— from 48,000 to 80 in the case of the 96% emulsion, and 6000 to 7 in the case of the 80% one. Continuous shaking in a bottle disintegrates both the benzene and the soap solution

ae a ws

ea % 2,

\S

HAAS 7 Cz

Fig. 58.—OPEN WIDTH SCOURING sanp CRABBING MACHINE. Yates and Wilkinson’s Patent.

(JAS. SLAITHWAITE, HUDDERSFIELD. )

into drops, and this latter is disadvantageous, the soap solution being the continuous phase. When benzene is dispersed into drops in the soap solution, the soap coats the drops and

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prevents them from coalescing. The first few shakes cause the most dispersion of the benzene, and the disintegration of the soap solution, and consequently the intermittent agitation

gives the best results.

OPEN-WIDTH SCOURING. Certain fabrics which are liable to rig or crease in the rope scourer must be cleansed while running flat or in the full width. Among such are light dress stuffs, clear finish worsteds,

+, eo. 6 te

VIZ ET A I

; > i US

7 I AS LN TS LALIT Li oy SS

( is

~ Sy ON St Teo 6 oe

Fia. 59.—OpEN-WIDTH SCOURER.

or even extremely heavily felted cloths which might be cracked in the dolly scouring machine. The open-width scouring machine has lightly built rollers, sometimes rubber covered,

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and with the pressure adjustable by springs; it is always fitted with spirally fluted or scroll rollers, to keep the piece fully open, and scrimp rails to maintain a proper tension for the same object. It is not so effective a dirt remover as the rope scourer, but the goods for which it is best suited are generally cleaner. Its output is of course considerably lower. The open-width machine is used in the hosiery trade for the scouring of continuous knitted fabrics. With some slight modifications, the ordinary rope-scouring machine may be used to wash pieces full width. For this purpose the back roller and draft board are removed, and a rail inserted, the width of the machine. This rail is of about four inch stuff and is tapered from the ends to the middle so as to give a crowning effect, as in a beit running upon a pulley. The pieces will be found to run with very little attention, and experience has shown on worsted and mohair fancies that successful results can be obtained by this device.

LOSS OF STRENGTH IN SCOURING.

In Chapter VITI, the changes in strength of fabrics due to the milling process have been fully treated. It was shown that there is always a real loss of yarn strength, which may or may not be regained by the felting up of the fabric. Similar conclusions apply to the scouring operation, but in a smaller degree. The diminished tensile strength of the yarn in these cases may be due to several causes :—

1. There may be a loss of fibre by friction, i.e., flocking. 2. There is undoubtedly a diminished interlacing of the fibres in the spun yarn; this is probably due to the fact that the yarn is continually under a longitudinal stress during the operations of scouring and milling (i.e., roller milling); that also the internal friction is diminished by the soapy liquids ; hence the lapping of fibre-on-fibre, which is the chief cause of yarn strength, is lessened. Mere steeping in water—or even extraction of grease by solvent—slackens the fibres and often lessens the tensile strength by a few per cents. Any mechanical working not leading to felting, e.g., un- twisting or unravelling action, will diminish it further, and the presence of tensile stress while under machine scouring and milling will contribute still more to the weakening. It is not necessary in such cases that

there should be chemical weakening of the wool substance.

Some further results from the Leeds University on the

scouring of yarns are here appended as of interest in this connection. :

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Fig. 60.—CLOTH CONVEYOR. (WriLLiAM BrircH, SALFORD, MANCHESTER.)

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The tests were all made from the same yarn, the greasy strength of which was 30 ozs. on an 18 in. test. When hand scoured in a solution of milling soap at 100°F. its strength fell to 21 ozs. In other words, it lost 30% of its strength. The same yarn scoured in a cold solution of soda 6°Tw. gave a drop in strength in 5 ozs., or 17%. The cloth tested was made from 10 sks. with 28 ends and picks per inch, and the greasy test was taken as registering 100°% of strength in warp and weft. The scoured cloth was tested and found to yield 83% in the warp and 67.4% in the weft, or an average loss of 24.8%. As the cloth was scoured at the same strength as the yarn sample scoured by hand, it is of interest to compare the two. Yarn fell from 30-25 ozs., a loss of practically 17% against 24% in the cloth, or an excess in the fabric over the yarn of 7%. If the yarn and fabric were scoured in a liquor of similar strength it might be expected that the loss in strength would be the same, but results show that there is a 7% increase, and further, that increase is in the direction of the weft. This action was at first thought to be a rubbing of the fibres in two directions, and to test this, two cloths were fixed on boards, one warp way and the other weft; the cloths were scoured: with a fair amount of pressure in the rubbing and continued for 20-30 minutes ; the cloths were washed-off in the direction of the rubbing, dried and allowed to condition. When tested, they showed no >» appresiabls difference, which disproved this idea. Another idea was that owing to the warp running in one continuous line, there would not be the same likelihood of these threads being damaged as for the weft threads which, in the ordinary scourer, would be subjected to a kind of torsional strain owing to the rope-like manner in which the piece is scoured. To test the action of a heavy roller on a cloth scoured under these conditions, one cloth was folded in the warp direction and pinned to a board, while another folded in the weft direction was pinned alongside, the cloths being then in a similar state as they are in the dolly scourer, the scouring was done by throwing the scouring liquor on to the cloths and then passing the roller over them, the cloths were then washed off, dried and allowed to condition. On testing the cloths, it was found that the cloth pinned in the direction of the warp suffered most in the direction of the weft and the opposite took place in the other cloth. A further test was made to confirm this result by scouring a cloth in the usual dolly scourer, one part of which was scoured with the warp running in the direction of the length, the other with the weft running in the direction of the length.

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The results of testing the two showed practically a reversal of conditions, i.e., the cloth running warp way suffered most in weft and the cloth running weft way most in warp. (Law.)

The Washing-off Process in Scouring.

There is a well-known mathematical theorem which has been developed in chemical work, mainly in regard to the washing of precipitates free from entangled liquors, which may serve as a basis for further discussion of the textile case. If a = volume of entangled liquid after draining, i.e., soap and dirt emulsion held in the interstices and capillary channels of the cloth. m = volume of liquid poured on for washing, then the total volume of liquid is equal to m + a. If x, is the concentration of the soluble matters in the original liquid, then the amount of substance left in after ”’ Ve 1S :—

& -) .aX, ; this will be less the smaller the multiplying m-+a

factor (a/m + a)", that is, “‘n’’ must be large. Theretore :— 1. There should be at the start a well-drained mass. 2. It is much better to wash often with small quantities than. to hued on a large volume at once, i.e., ““n’’ is to be large, “*m ”’ small. Now the textile differ in many respects from this theoretical case. In the above, the assumption is made that the impurities to be removed are soluble, whereas the usual situation in textiles is that of dealing with an emulsion and adsorbed impurities. In this case it is absolutely essential to proceed at first by slow dilution of the emulsion to a lower concentration in order-to avoid coagulating the scour and precipitating these impurities which would settle again on the fibre. In piece scouring this can be well achieved, and there are two methods used in practice :— 1. Use of a sprinkler pipe. 2. Diluting the scouring liquor directly. In the second method the washing-off water is led into the scour at the bottom of the machine, often under a grid; a progressive and graduated dilution occurs, the first effect usually being to raise the lather; the weakened emulsion is then run out of the machine. With a sprinkler pipe, the wash-off water is discharged on to the fabric passing just in front; that portion of the cloth and scour carried with it is immediately strongly diluted, and the excess water falls into the scour below. There can be little doubt that the method of diluting the scour directly is preferable and practical working

Page 281

- Fig. 61.—B-TYPE WOOL WASHING MACHINE

(PETRIE & McNauGut, ROCHDALE.)

257

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over extended periods has proved its reliability. In each case a second point of detail arises. After the lather has risen, the - scourer opens the shuttle to the drain and runs off the excess. Is it better to do this continuously or to close the shuttle now and again, allow the liquid to rise in the machine, and thus draw off intermittently ? In other words, to proceed by down and concurrently drawing off, or by flushing ? The point is not so important as that above, but it is probably desirable to wash down by a series of flushes. In the scouring of raw wool in the usual set of bowls, it is plainly impossible to conform to the theoretical principles of washing. The masses of wool fibre, with their attached scouring liquor, after a simple squeeze are plunged straight into a very large volume of water where the comparatively slow process of diffusion is left to complete the washing off. The prime necessity for avoiding felting governs all the pro- cedure in this case, but it is an interesting question whether an application of the sprinkling and draining principle would not be useful in this connection. The reason that raw wool is satisfactorily scoured on the present lines is probably to be found in the great subdivision of the material, facilitating easy penetration and escape of the detergent medium. The nature of the impurities in raw wool makes their removal a comparatively easy matter, as compared with other commonly occurring cases, e.g., the scouring of low woollens. The ready emulsifying power of the wool fat (lanolin), the free solubility of the wool sweat (i.e., the potash salts), and the large pro- portion of the dirt, which is mere mechanical contamination, all these factors make the scouring of wool a problem of lesser difficulty. It has been mentioned that quite large proportions of the dirt are removable by ordinary steeping, and it is now the tendency to raise the temperatures of the scouring bowls to secure the complete melting of the impure lanolin—the melting point is about 110°F.—and bring a larger amount of extraneous matter away. A further development on these lines is to separate from the emulsions obtained the solid matter and the grease, and use again the remaining liquor as a scour. This is the so-called Scouring by Natural Emulsion. It is said that from practically every standpoint the results are superior to those obtained by the usual soap and alkali procedure. The following advantages are claimed :— COST is very considerably reduced, and with the machines suitably arranged the consumption of soap and alkali will be only about 20% of what has been customary. COLOUR.—This is unquestionably improved, the finished wool being both whiter and brighter. CONDITION.—Wool scoured in this way is more free, open and lofty, and works better in all the after processes, resulting in less noil and waste.

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I

er er ae eet ee er er eral a eat es ar ana 1

Fig. 63.—NON-SELF-CLEANING BOWL.

(PETRIE & McNavucut, Lrp , RocHDALE.)

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REGULARITY.—It is much easier.to maintain a regular and even degree of cleanliness. EASE OF WORKING.—The whole process being rendered more automatic, the scouring attendant has: much less work to do. GREASE WORKS.—Where the effluent has to be treated, the quantity of acid for “ cracking ”’ is greatly reduced, the sandy deposit is cleaner and less bulky, and a finer grease is obtained. Instead of emulsifying the grease of the wool by the usual ‘method of employing soap, soap and alkali, or alkali alone, as emulsifying agents and working at a temperature of about 120°F., the new method makes use of the natural features of the grease, and no soap or alkali is used, except in the final stages, to remove the small portion of grease, etc., not naturally detached. In the first bowl of the scouring machine, only water is used, but at a temperature of 145°F. (Cf. previous paragraphs on the detergent problem in wool scouring.) At this temperature an effective natural emulsion is formed, and the wool, after passing through the first squeezing rollers, is to have lost about 50° of its original grease and most of its original soluble salts and earthy matter. In the second bowl, also, only water is used, and at the same temperature. On leaving this bowl, the grease content of the wool is reduced by about 75%, and very little other dirt remains. In a large plant a third bowl can be employed in the same way. In the next bowl practically all the remanent grease and dirt are eliminated by the usual method of emulsification in a soap solution, which may consist of the common 0.5% solution (4 to 5 lbs. of soap to 100 gallons of water). This soap solution not suffering much contamination by dirt or grease, may be used for a long time, and it is only necessary to add sufficient fresh water and soap to prevent the liquor becoming over- charged with grease, i.e., it is necessary to maintain the proper condition of emulsification. This depends entirely on the amount of wool and its grease content. Following this soap bowl, a further bowl is required as a rinser. It is stated that, working on these lines, alkali can be entirely eliminated and the soap consumption may be reduced to 14 lbs. per 100 Ibs. of clean wool, when dealing with greasy merinos, and to about 1 lb. per 100 lbs. when scouring crossbreds. It is nearly certain to be beneficial to use a little alkali in the first soap bowl (see paragraph on the functions of alkali in scouring), and possibly-in the others ; the use of alkali in general scouring has very probably been overdone. It will be noticed in this natural emulsion system of wool scouring that the bowls work distinctly better after a while, when the liquor has become somewhat charged with matter from the wool.

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The ideal is for the “‘ water ’”’ bowls and the “ soap ”’ bowls to maintain a constant condition of emulsification. This requires that the bowls must not be periodically run off and refilled, but that there should be a regular inflow and outflow to each bowl. The system of self-cleaning, adopted in the new Petrie & McNaught plant, is peculiarly adapted to scouring by natural emulsion. Indeed, practical trials have shown that so little dirt passes beyond the second bowl that the following bowls need not be let off for cleaning more than once a week. For the proper working of this method, at least four bowls must be used, and there is advantage in adding a fifth. The

Fie. 64.—AUXILIARY DELIVERY MOTION FOR WOOL WASHING MACHINE. (PETRIE & McNAauGuT, ROCHDALE.)

cost of soap with five, four and three bowls is said to vary approximately in the ratio of 1, 14 and 3. The quantity of water needed in the natural emulsion bowls depends on the wool being treated ; when sufficient wool has been put through to bring the liquors up to the desired concentration and emulsifying property, the discharge from the first bowl is arranged at a suitable rate, say, about 250 gallons per hour, when dealing with greasy merino wools at the rate of 1,000 Ibs. per hour. This is replaced by fresh water. The liquors of the soap bowls are worked together, the discharge from the first “‘ soap ’’ bowl—say, 200 gallons per hour—passing to the

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drains and being replaced by a corresponding amount from the second ; this second soap bowl is replenished by addition of fresh soap solution. In further modifications of natural emulsion wool scouring, the liquors are taken, sedimented, centrifuged free from grease, and then returned in whole or part (with or without

Fie. 65.—VIEW OF SCROLL OF SELF-CLEANING WASHING MACHINE.

(PETRIE & MoNavuaeut, LTp., ROCHDALE.)

addition of fresh water) to the various stages of the plant. It should be noted that wools which have already been washed or steeped, such as Colonial Scoureds and Slipes, are not adapted to this system, but only wools retaining their natural grease ; when blended with greasy wool, however, the former varieties may be dealt with. As a description of methods employed in the extraction of lanolin, the following matter, taken from the Scottish Tweed Book, October, 1923, is appended :— ‘‘ The suds from three scouring sets working only on merino

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wools are run into a well holding 18,000 gallons, and this is pumped up to fill one of three 6,000 gallon settling tanks on the roof of a shed. Here the sand, etc., is allowed to settle and the liquor run off by means of a floating pipe, to get the liquor from the top first ; these suds are run into a tank of approximately 300 gallons continuously and maintained at a temperature of 160°F. Under this tank are six ordinary cream separators through which the heated liquor runs. The _ lanoline comes out at one spout and is pumped up to a couple of purifying tanks made of wood, of a capacity of 500 gallons each. The rest of this extracted liquor goes with the suds from the ‘crossbred’ bowls, to be cracked in the ordinary way. The crude grease from the separators contains a certain amount of soap and fatty acids; these latter are saponified with Caustic Soda and the whole washed with water, to remove all soap. The amount of fatty acids is determined in the usual way, and the quantity of Caustic Soda required is added, well diluted, in three separate lots. The washing is carried out with warm water in two separate washings, stirring well up, the 250 gallons of lanoline being made up to about 450 for the washing. When washing is complete, a little time is allowed for settling, and cold water is run into the bottom of the tank until the lanoline overflows into the next tank. Bleaching follows, generally by Sodium Peroxide. The yield is about half a ton of lanoline per 8 hours from 18,000 gallons of liquor.”’ It is evident that problems of wool scouring—now receiving much-needed attention—raise anew all the questions of soap hydrolysis, retention of alkali by wool, formation of acid soaps in detergent liquors, etc. As there have been questions of priority of discovery raised in connection with these matters, it is reommended to refer to the chapters in this book on the theoretical side of detergent scouring; much of the recent work on these problems is only extension, possibly more accurately carried out, of the researches of earlier workers in the field. Dr. O. Herzog, in discussing the structure of animal hairs, points out that there are at least three layers : Cuticle, Cortex and Medulla, as is well known to all workers on the histological side ; he asserts that these layers are distinguished in their chemical properties. For example, Von Brunswick has found that the outer layer of wool hair does not give the so-called diazo-reaction which is given by the inner layers. As it is easy to remove the outer scales by a process of abrasion, this result may be easily confirmed. Again, the wool fat plays an important part in the general structure and behaviour of the fibre. If this fat is completely extracted, the hair is seen to be of a capillary nature, the fatty matter having been previously distributed throughout the whole hair. A moderate

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magnification, < 500, on a fibre with the scales removed, shows the porous structure. Now the lanolin grease is, as shown elsewhere (see Wright’s results on absorption of moisture) very absorptive of moisture, swelling up in the process ; it is therefore certain that this absorption extends to other com- pounds, e.g., alkali, soap, etc., and that the process of emulsification in scouring includes this factor. Hirst and King have revised much of this problem, and have confirmed that in the case of Sodium Oleate, for example, the Sodium Hydrate is removed by hydrolysis and is absorbed by the wool, that further soda is released and that the acid soap thus produced is partly suspended and partly absorbed. They show that there is a “ of soap by clean wool, and that the alkali is removed predominantly ; the difference between absorption of alkali by wool from soap solutions and solutions of alkali alone is merely a question of degree. Inert materials, such as crockery, do not show this property, and ‘vegetable fibres, such as cotton, exhibit it to a less extent. Methods have been evolved, based on the use of Terephthalic Acid, for the quantitative estimation of acid and alkali in wool. From a 0.01% solution of Caustic Soda wool picks up about 0.4% of its weight after two hours’ immersion at ordinary temperatures, and three-quarters of this absorption occurs in the first ten minutes. The work of Speakman has confirmed the conclusion stated in the previous edition of this book that this combination—a sodium keratinate—would be analogous to the corresponding sodium caseinate. It must be well realised that this hydrolysis alkali is absorbed from all or any solutions (soaps, soda ash, borax, silicate of soda, or special detergents containing these) to a certain extent. It is of interest to note that there is a standard allowance for dry combed tops of 0.634°% of wool fat, and soap residues and insoluble matter. Townsend says that up to ? of 1% of yolk left in wool after scouring is beneficial. I It thus appears that the ordinary soap and alkali scouring is capable, not only of removing dirt under normal scouring conditions, but may in abnormal circumstances contribute matter—residual alkali or fatty matter—to the fibre. It often happens that scoured pieces, from accidental contamina- tion, may require rescouring ; such cloths may be even more difficult than ordinary greasy goods. The writer may cite, as an illustration of this, a number of white worsted serges and gabardines, bleached in peroxide and finished out, which, by gross carelessness, had been exposed without protection in a Bradford warehouse, and had consequently acquired along all ‘the exposed cuttled edges a fine deposit of the soot of an industrial urban atmosphere. It may be that extremely finely divided matter of this nature is capable of actually

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penetrating the capillary pores of the fibres, or of lying em- bedded in the surface irregularities, but it is undoubtedly the case that such a problem constitutes one of the most difficult situations which can confront a scourer. Only by the most painstaking handwork in the way of local treatment, with special detergent solutions, were the pieces in question refinished. : There is always the temptation before the scourer to increase the strengths of his solutions when difficulties are encountered. Mr. Burford Petrie, in a lecture to the Huddersfield Textile Society, cited two cases within his personal knowledge of large firms, one of which in scouring wools of merino quality uses alkali alone in the first bowl and on crossbreds soap only ; the second firm stated that their practice, founded similarly on practical experience within their works, was to employ a soap bath only for merinos and soda ash alone for crossbreds. When actual works’ practice on the large scale can diverge to an extent illustrated by these instances, it is full time for scientific research into the bases of these technical operations. What seems to be most necessary in the scouring of raw wool is the formation of perfect emulsions by the best means possible, either natural or artificial. Veitch and Benedict (Text. Mfr., Oct., 1925) in an examina- tion of wool scouring liquors, state that purified wool fat consists of approximately two portions :— (a) One of melting point 60°C. (i.e., 140°F.), insoluble in alcohol and unsaponifiable. (6) One of melting point 15°C. (60°F.), soluble in alcohol and unsaponifiable. It is evident that the first component will require an emulsification at a temperature above its melting point. In a paper on “ Lanoline Extraction from Suds ” (Text. Mfr., Aug., 1920) some figures are given of general interest from the present standpoint. Taking an average basis of raw wool :— Fibre 45%; Fat 6%; Soluble Yolk 20%; Dirt 15%; Moisture 14%. The scouring of a full shift of 4,000 Ibs. of this raw wool is assumed to yield 15,000 lbs. of sud containing 150 lbs. of fat, 700 lbs. of soluble yolk, and 570 lbs. of dirt approximately. It is estimated that nearly the whole of the dirt and about one-third of the fat with it would be separated by simple sedimentation and skimming. The writer continues, “‘ A good centrifugal clears out not only the fat, but the remains of the insoluble dirt, so that the speculation arises, COULD THE SUD THEN BE USED OVER AGAIN ? But it is very evident that the sud could be used over again to a certain extent, this extent being determined by trial under the actual conditions prevailing in

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the works. Perhaps an addition of 50% of fresh water, or possibly 75% of fresh water would provide a suitable recipe. In any case, a very appreciable saving of soap is easily possible.”’ The Duhamel *“‘ Natural Emulsion ”’ system of scouring raw wool employs the principles elaborated in the foregoing discussion. The bowls are of much smaller capacity than the average English plant, and are designed with special settling troughs, combined with gearing, to allow of regular discharge of the sediment. Liquor contaminated by grease is separated on lines similar to those described above, the lanoline being - recovered ; the scour remaining is pumped to a reservoir and is fed along with the raw wool by a conveying device to the first bowl. A second bowl contains plain water, the third is a soap bowl, and the fourth a rinsing bowl. The process is continuous in respect of both recovery of the grease and supply of the liquor, water, etc. The following notes have been supplied by Messrs. Petrie and McNaught for working their machines by emulsion methods :— When this system of wool scouring is employed :— (a) The quantity of water, soap, etc., required depends mainly on the amount of grease to be removed from the wool. Hence, an estimate of this, based on the weight of wool and the percentage of grease, should be obtained ; thus, if washing 1,000 lbs. of wool per hour containing 15% of grease, there will be 150 Ibs. of grease to be removed per hour. This is the “ grease content,’ and in the following matter soap and alkali are given per 100 Ibs. grease content. For such a grease content of 150 lbs. per hour, these quantities would all require increasing by 50%. (6) When the scouring plant consists of four bowls, the first bowl is supplied with a constant inflow of fresh water at the rate of about 200 gallons per hour. (Grease content of 100 lbs. per hour.) The second bowl requires a constant inflow of about 100 gallons of fresh water. The third bowl should be supplied with a flow of water taken from the fourth bowl at a rate of 250 gallons, with the addition of 8 lbs. of soap and 5 lbs. of soda ash. The fourth bowl requires 250 gallons of fresh water, to compensate for the amount passed back to the third bowl, and 2 lbs. of soap.

(c) In the case of a plant consisting of five bowls, one of two methods may be adopted. In the one which gives the most effective scouring, but is less economical, and

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which will be found best suited to greasy merino wools, the first and second bowls are operated as above. The third bowl will be supplied with a flow of liquor from the fourth bowl at the rate of 200 gallons, and requires the addition of 4 lbs. of soap and 4 lbs. of soda ash. The fourth bowl needs 200 gallons of water from the fifth bowl, to replace the amount passed to the third, along with 4 lbs. of soap. The fifth bowl requires 200 gallons of water, to replace that passing back to’the fourth, with or without the addition of a little soap, as preferred. The alternative method of working with a five-bow] machine, suitable for wools more easily scoured, is as follows :— The first and second bowls, as above. The third bowl, water only, at the rate of 100 gallons. The fourth bowl requires 44 lbs. of soap and 3 lbs. of soda ash and 150 gallons of liquor taken from the fifth bowl. The fifth bowl requires 150 gallons of water (to the amount passing to the fourth) and 14 lbs. of soap. (d) When starting up with clean water, the addition of water is not required in any of the bowls until sufficient time has elapsed to make the corresponding additions equal to the bowl capacities, i.e., if the wool being washed calls for 300 gallons an hour and the capacity of the bow] is 1,200 gallons, no addition would be required for the first four hours. Addition of soap and alkali should obviously be made from the commencement. When starting up the first soap bowl should contain 3 lbs. of soap and 14 lbs. of soda ash per 100 gallons bowl capacity, assuming in each case that soft water is being used. If the water is hard, additional soap will be required. (N.B.—And soda also.—Author.) (ec) Some trouble may be experienced when starting up after a stoppage, due to the wool sticking at or wrapping round the rollers. Too overcome this, throw a bucket of soda ash solution on to the wool entering the rollers, and probably no further trouble will be experienced. (f) It may be advisable to use less pressure on the first and second rollers than usual. A pressure of 2 to 3 tons is sufficient, and may be found preferable to a heavier pressure. (g) The temperature of the first and second bowls should. be kept up to 145°F. <A lower temperature, 135°F., may be used in the third (soap) bowl, and 145°F. if worked with water only.

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(2) If only three bowls are employed, this system of scouring may not produce sufficiently clean wool, but if the first bowl is used as described and the second and third bowls are used as for a four-bowl machine, but with twice the amounts of soap, alkali and water, it may be found that, compared with usual practice, the results are both better and cheaper. («) To take full advantage of this method of working, four or five bowls should be employed, and the first and second should be of the self-cleaning type. With the non-self-cleaning plant it will be found that the first and second bowls can be worked 24 hours in many cases before it is necessary to empty the bowls to clear away the deposited sand. When the first bowl is cleaned out, it should be refilled with the liquor from the second. The third and following bowls only require to be cleaned out once a week. (j) The side tanks of the first and second bowls should be cleaned out twice per day. (k) Automatic steam control valves should be fitted, to ensure the maintenance of correct temperatures, and flow meters to indicate the quantity of water admitted. (1) The foregoing quantities of water, soap, etc., are neces- sarily only approximate, and may require modification by the scourer’s judgment. The discussion of the methods of natural or emulsion scouring, given above, must seem strangely reminiscent to persons of long technical experience in the trade, and must provoke the reflection that any novelty in working resides rather in combination of systems and devices than in original principles. The practice of using scouring liquors over again, for example, is of long established standing in both wool and piece scouring ; it has been customary to pass clean or only partially exhausted scours from one bath to another. The writer, within the last year or two, listened to the complaints of an employer that the scouring staff ran away to the drains good soap liquors which his father would have retained to do a preliminary scour on much fresh wool. It has also been common—and doubtless still persists—in scouring the fairly clean worsted piece goods to keep the soaping-up liquors in a special tank and begin the next batch of pieces therewith. The question of temperature is fairly obvious. As pointed out in the *“‘ Wet Processes of the Wool Industries,’’ in dis- cussing this matter the critical factor is the melting point of wool fat, 40-45°C., or 104-113°F. It is mentioned that Colledge conducted some scouring experiments at 180°F., etc. It is undoubtedly the case that much wool goes forward from scouring containing a little grease and is spun—possibly not

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much the worse for it—and woven, being only really cleaned when passing through the operation of piece scouring. It will probably be a useful subject of enquiry how far the fibre

should be stripped of the ‘“ Natural ” fat before it is worked up into yarn and woven cloth.

Another curious factor mentioned in this discussion is the slipping of the wool at the first rollers, which reminds one of the similar—and probably identical—phenomenon sometimes occurring in the Saponification scour when, by over-warm alkali, the stripping of the wool oil proceeds too rapidly for a

i}

= 3 52 ES =

Fig. 66.—SCOURING MACHINE WITH ADJUSTABLE

PRESSURE. (JAMES BAILEY, SLAITHWAITE, HUDDERSFIELD. )

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Fic. 67.—SCOURING MACHINE.

(JAMES BaILEy, SLAITHWAITE, HUDDERSFIELD.)

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proper emulsification. The use of the centrifuge on wool liquors for the recovery of lanolin and for the purification of seak liquors has been a subject of experiment for many years past in the wool industry ; in the converse aspect of treating a scour for re-use it may be novel. As the power requirements for high-speed centrifuges are not small, this factor will require taking into account and fairly long working trials needed to determine the costs. The close specifications of temperatures in these large scale workings are somewhat doubtful, and arouse curiosity as to how far actual practical wool scouring is conducted within these limits.

The present interest in emulsions and colloid phenomena is bearing fruit and the working of the scouring bath is becoming better understood. Polonovski has centrifuged a washing liquor, collected the impurities from the walls of the centrifuge and determined the relative quantities of soap in this: layer and in the residual liquor ; nearly the whole of the soap was in the solid impurities. As was previously known, the im- purities become coated with the colloidal soap, and there is also a decomposition of dissolved soap. In very dilute solutions of soap the colloidal coating of the dirt particles is thinner; beyond a certain thinness, the emulsified state cannot persist, and the soap available is in solution and subject to hydrolysis. The converse condition of excessive dirt, beyond the power of the bath to emulsify, is not uncommon in practice. Such liquors must be removed from the general bath ; it is preferable to take the squeeze from the rollers, for example, straight to the drain rather than return it to the bath. Such scour, strongly charged with dirt, grease, etc.., from the adjacent fibres is a strongly concentrated emulsion in comparison with the average scour of the bowl, and should not be returned thereto.

It is a well recognised feature of the roller milling machine that pressure is applied to the milling rollers by powerful springs, and the opportunity of varying the pressure of these springs is a valuable aid to proper milling. Thus, in milling certain crossbreds, a comparatively light pressure must be employed. The corresponding point in scouring does not seem to have been so well appreciated, but it is equally valuable, and in the rope.scouring machine, figured in these pages (see Figs. 66 & 67) such a variation is possible. By a bevel and screw feed, the compression of the springs on the bearing blocks of the upper rollers can be adjusted and the machine thus adapted for scouring the lighter worsteds or alternatively giving a partial milling along with the scouring on of all types. If the pressure is released until there is a sufficient grip to take the pieces round and through the scour,

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then many pieces ordinarily put through open-width scouring may be done in rope form, with much increased output and certainly not diminished perfection. In a machine which is capable of these modifications, and thereby adapted to a large range of work, running costs are saved, floor space, power, etc., economised and general efficiency promoted. The rope scourer, properly arranged and utilised, is the mainstay of the piece scourer’s plant ; by using enough pieces to carry the weight of the rollers, reducing the roller pressure as above, the danger of crimping and marking cloths may be avoided.

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MILLING.

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CHAPTER VIII. Milling.

WOOL

is unique among the textile fibres in respect of its property of milling or felting. The objects of the milling process are :— 1. To gain fabric-strength by the felting action of the material ; a cloth has considerably more mechanical strength in the milled than in the loom state. (But see later.) 2. To achieve certain special finishes, i.e., surface effects unobtainable otherwise than by the felting action of the process ; for example, the “ blind finish ”’ of cloths such as Meltons with the obliterated weave as con- trasted with a clear-cut worsted finish. 3. To increase the density or weight per unit length of the cloth ; as in billiard cloths, rugs, flannels, blankets : for special purposes of resistance to weather (wind or water), as in submarine cloths, filtering fabrics, feltings for hats, etc. The supposition that “‘fulling is the process of making the cloth fuller or denser is a common error; “ fulling ’’ is derived from the French ‘“ fouler,”’ to tread or trample, and comes from the old practice of walking or trampling the cloth to secure felting. 4. To obtain “handle,” i.e., softness, by producing a “cover”; this is sometimes merely a slight crushing of yarn, as in estamene serges, rather than a felting operation on fibres. It is the object primarily sought in the process of raising. I 5. To obtain the advantages of relatively superior finish while permitting the use of inferior materials, e.g., the use of cotton warps with weft of recovered wools. 6. As a necessary preliminary to the raising process. Compare the manufacture of a flannelette. 7. To produce a fabric by a cheap process, as in the pro- duction of carpet and roofing felts and the like, thus dispensing with the production of yarns.

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Theories of Milling or Felting.

The question of why wool felts has in the past been a subject of much controversy, and it is more probable that it is the resultant of several factors than an effect of any one isolated cause. There are three hypotheses usually put forward :— The Serration, Adherence, and Interlacing theories.

SERRATION INTERLACING OF FIBRES IN LoOcKING, FIBRES. FLEECE. Fia. 68.

All these are based upon well-established specific properties of the wool fibre. The serration theory, for long the most generally accepted, considers that felting is due to the inter- locking of the imbricated scales forming the exterior of the fibre. This very natural assumption appears at first sight to be strongly supported by certain broad facts.

True hair is typically non-imbricated and has little or no felting property. Merino wools have abundant scales, as many as 2800 per inch, Southdowns have about 2000, while coarse Lincoln wools have only 600-1400 to the inch. The felting properties of these wools are in the same descending order. There is considerable variation in the scale formation in different wools ; in merino wools they are relatively large, sometimes enveloping the whole of the fibre as cusps, and their edges may be free for as much as a third of the scale-length. The pointed ends of lamb’s wool are devoid of scales. The free opening of the scales is increased by acid or alkaline treatment, or even by hot water. Further support was lent to the serration theory by the “creep” or “ crawl’ exhibited by the fibre when rubbed between the finger and thumb, the fibre travelling in the direction of the root. Ina paper on the * Felting of Wool ” (Textile Manufacturer, 1906, pp. 66, 67), Ireland points out that the skin end of the fibre felts first. O. Fiske, in the

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“Textile World Journal” (26th July, 1919), the author states :— “In every pressure and action brought upon the cloth in the fulling process this tendency to crawl is operative. Experiments were made on selected locks of wool in which the fibres retained their original position, and after careful scouring lay as in the fleece. Two locks were cut near the pelt end, and the pelt ends wrapped together in cotton cloth to undergo fulling. Exactly similar treatment was given to the point ends of two locks cut near the point ends. After fulling treatment it was seen that the pelt ends were securely felted together and the point ends quite separate. In the latter sample, however, a hard felt was formed at the extreme ends of the locks nearest the pelt. In locks from the fleece, therefore, felting begins at the skin end, and continues gradually—the fibres all lying in the same direction—towards the point end. The same wool, after carding with pelt and point ends in both directions, gave equal felting throughout, and more quickly and perfectly than when in locks. By cutting sections at different distances from the skin end, it was found that what was then the skin end felted promptly, regardless of the distance originally from the actual skin end.” In spite of the general tendency of these results, the author sums up :— “The old theory of fulling, viz., that scales of adjacent fibres work under each other and become entangled is not borne out by these facts, because the crawl or movement is in the wrong direction to interlock. Instead, it is concluded that the first action of an individual fibre is for the skin or pelt end to fasten itself to one or more other fibres. This is followed by the forward movement of the fibre in the direction of the skin end. This end being secure, the remaining part of the fibre must of necessity curl and kink among the other fibres. Fibres which have been carded allow of the first fastening action occurring at every point in the mixture, and then follows crawling and curling and increased closeness. All loose fibres on well-felted cloths are point ends. Careful napping, therefore, produces a condition like wool on the sheep’s back, with the fibres pointing

Again, under the action of chlorine gas the scales of the fibre suffer erosion and mill badly, and have fewer and more irregular scales, or have them cemented up. The other principal textile fibres, cotton and silk, have no development of scales, and are quite non-felting. In general, therefore, the interlocking-of-serrations theory appears at first sufficient to account for the felting up of wool fabrics during the milling or analogous processes. It is, however, certain that it is not fully adequate to the case. It must be remembered that the projection of the scales from the surface of the fibre is quite small, not more than 3-4% of the fibre diameter; in the finest merino, less than 3545, of an inch. The theory further neglects another important element in the structure of the wool fibre, viz., its waviness, crimpiness, or curling. A fine merino wool might show about thirty of these crimps or waves per inch of its length, a coarse wool one or two only. The worsted spinning process tends to eliminate these crimps.

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The following tables, due to Bowman, give useful comparisons :—

NATURAL CONSTANTS OF WOOL FIBRES.

TYPE OF WOOL. DIAMETER SCALES OF FIBRE. PER INCH. East Indian 0.00143 1000 Lincoln 9] 1400 Southdown 80 1500 Merino 55 2000 Saxony 50 2200 caer die i DIAMETER WAVES OF FIBRE. PER INCH. English Merino 0.00064 34-30 Southdown 78 13—18 i 100 11-16 Trish : 120 TTT ' Lincoln 154 3—5 Northumberland F732 2-4

The serration-interlocking theory takes no account of this curliness ; but it is at least as probable that interlacing by waves having a pitch as coarse as of an inch produces felting, as that the interlocking of minute scales 3,55 of an inch total length, free edges 3,4,5 of an inch, and projecting only 35355 of an inch from the fibre surface is the prime cause. This waviness of the wool fibre is temporarily removed by wetting with hot water, but returns on drying ; if dried while stretched, it is entirely and permanently removed. It must be noted too, that as in the case of the serration theory, the order of felting property in wools is generally the same as the order in which waves per unit length are present. It is common knowledge that a coil of rope, wire, or even knitting wool, can become involved into an inextricable tangle; so, of course, will a barbed wire, but the presence of barbs is not essential to the intermeshing. We are therefore brought to the third hypothesis of milling or felting, viz., by interlacing of fibres assisted by the crimpiness of the individual fibres. A further table, comparing the sortings from a German merino wool, is appended :—

WAVES NO. QUALITY. PER INCH. DIAMETER. 1. . Super Electa 27-29 1/840 2. Electa 24-28 1/735 3. Prima 20-23 1/660 4. Secunda prima 19-20 1/588 5. Secunda 16-17 1/534 6. Tertia 14-15 1/510 7. Quarta 12-13

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‘Thus the finer the wool the greater the tendency to curl, and in general the greater the milling property, as, a priori, the greater must be the tendency to interlace. Mr. N. Burgess, in a paper read before the Quekett Microscopical Club, in 1867, said :—

“*Tf a fibre be taken from the Merino and another from the Lincoln sheep, and be laid side-by-side, the relative proportion of their curves—i.e., their waves, curls, or crimps—will be as 15 to l. Ifa number of these fibres were taken, each sort separate, it would be seen that the amount of entanglement between the fibres would be fifteen times greater in the one case than in the other. _Suppose that instead of their natural form they are laid parallel to each other in a straight line by machinery, each fibre has a natural tendency to regain its original position. Suppose the now parallel fibres are twisted into a yarn and then woven and the warp is strained tight in the loom, many of the loose threads having been stuck down in the sizing process, it is evident that in this condition all the fibres are in a state of unnatural tension until they come out of the loom in the form of cloth. All external tension is now removed in order for the next or felting process; the loose fibres being released and the cloth being saturated with moisture, the whole has to undergo a process of heavy thumping during which each fibre has a pressure applied first in one place and then in another. I believe that each fibre at every stroke is doing its utmost to gain its curved condition, and as it does so, the cloth contracts and becomes thicker. This thickening is in proportion as the fibres of the wool have resumed their curved form from the temporary parallel condition ....... If imbrications go for anything, then Russian Donskoi should eclipse every other in felting, but here again facts are dead against that theory.”

The author’s views seem, for the date at which they set forth, remarkably accurate and rational. It is now more probable that the increase of strength is gained by the fabric in the drying-out stage after milling ; the fibres, then released from their plastic and turgescent state, redevelop their latent crimpiness, together with the elasticity and tenacity proper to the natural fibre; and to this is superadded the inextricable intermeshing produced by the mechanical action of the fulling process. -The negative factors of the serration theory, i.e., the absence of felting in silk, cotton, etc., do not prejudice the present theory of general matting or interlacing of fibres, nor do likewise the deductions drawn from the special action of chlorine. . Direct microscopic evidence of serration-locking, i.e., meshing as of teeth of gears, is difficult to get in a structure like a textile fabric, the high magnification and depth of focus required being largely incompatible. Some interesting observations on wool felting are given in a paper by Dr. T. W. Woodhead, The Microscope and its Uses for Textile (Jour. Huddersfield Tex. Soc., 1908-9, p. 36). After criticising Bowman’s conclusions, the author proceeds :— * Although much has been written on the subject, I have not been

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able to find a good account of the appearance presented by felted wool when examined under the microscope. The slide exhibited shows a portion of closely-felted wool, and even a casual examination shows that not only are the fibres much curled, but that they cross and recross each other very freely. The other slide shows a portion of hat felt. Here again, we see that so far from interlocking, the great majority of the fibres cross each other, often at right angles. What microscopic examination tells us, therefore, is that the more complete the felting, the greater is the tendency for the parts of the curled fibres to place themselves more and more completely at right angles to each other. So far from the microscope misleading us in this connection, one of the most familiar experiences of those who have examined felt under the microscope, is the difficulty of finding fibres with interlocked It is quite practicable to arrange tests of the nature of crucial experiments to decide the validity of the several felting theories. Harrison, for example, arranged a bundle of wool fibres in halves with the serrations pointing in opposite directions ; they were tied at the ends to prevent slipping, soaped, and put into an indiarubber tube to check entanglement ; milling was performed in a set of experimental stocks. It was found that no felting took place. A similar bundle in a tube, but arranged to allow of entanglement, milled quite readily. ‘‘ In another experiment, two ,bundles of fibres with the ends fixed to prevent slipping were stitched to a cotton fabric so that they crossed one another at right angles; after treatment in the stocks the portions crossed were milled, but the free portions of the fibres where entanglement could not take place, were not milled at all.’’ The old notion, still current in rule-of-thumb circles, that shrinkage was the cause of felting is a curious inversion of ideas ; the felting is the cause of the fabric shrinkage. Prof. Barker, in a public lecture, incidentally referred to the principles of wool felting :— ‘In the light of results obtained on an instrument, the idea of which he had obtained in the Lowell Textile School, but which he had much improved upon. This instrument revealed that the felting of wool was principally a bending, and not a fibre contraction process. Thus weave and setting might be looked upon as the means whereby the necessary bends or crimps were given in the fabric, and the felting process the means whereby the fabric upon these bends was given its accordion pleats. In heavily milled fabrics it has been I found quite possible to get back to original warp lengths. Felting did no doubt consist of fibre shrinkage, fibre curve, and thread curve, and of these the first was in many cases almost negligible.” Consider again the factor of yarn structure, i.e., the worsted v. woollen type. In the former the wool fibres are made to assume a mutual parallelism, the tips of the scales probably pointing fairly equally in both directions. If interlocking ot serrations was the principal factor of felting, then, a priori, the worsted thread should be well designed to this end. But all practical experience is the other way. In the woollen

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thread there must be, in the nature of things, fewer contact areas where the serrations are opposed or suitably situated to secure interlocking ; yet woollens are the milling fabrics par excellence. The second theory of milling, that of fibre adherence, assumes a state of plasticity produced in the fibre by the combined effects of moisture, soap, temperature, etc., during which adhesions, facilitated by the mechanical action, of adjacent fibres result; which adhesions, persisting in the felted fabric, cause the shrinkage. Justin Mueller, in a paper on the “ Felting of Wool,” (Rev. Gen. des Mat. Col., 1909, Mar.) states that :— ** Prolonged boiling or use of too much acid in dyeing are known to cause felting, the changes being perhaps due to the gelatinising of the fibre ; if mere mechanical manipulation, it would at least be as well done in a dry state.” In certain experiments, with fibres fastened to glass agitators so as to retain their positions, he claims to have proved that wool may become felted without mechanical agitation, that felting is favoured by addition of acid to the bath, that in calcareous waters it is more pronounced than in distilled water and that a slight addition of acid to calcareous water inhibits the felting just as a greater quantity favours it. the felting of wool is induced by acid and alkaline bodies which affect the fibre in such a manner as to gelatinise the surface.” (Presumably with subsequent adhesion.—ED.) In criticism of the adhesion theory, it may be said that it is true that wool has its surface “‘ gelatinised ’’ by moisture, heat, and certain reagents ; it is better to say that the fibre is in a state of TURGESCENCE ; that is, it is a colloid which has swollen by absorption of water, etc. It is certain, however, that any material amount of adhesion produced by this means would again be greater in the worsted yarn fabric than in the woollen type. Even more than in the serration hypothesis should the parallel lie of the fibres in the typical worsted structure favour this adhesion theory ; yet all the facts of practical manufacture are against it. In the “ Finishing of Textile Fabrics,” Professor Robert Beaumont says :— ‘“‘ In experiments, the yarn constructed on the woollen system made a fabric better adapted for milling than that on the worsted system. Instances where a fine merino wool was spun to the same counts by carding, and spinning on the self-actor, to a similar yarn made on the worsted method, and also woven into a fabric of the same structure. THE WOOLLEN HAD THE HIGHER FELTING PROPERTY. As an example of this, reference may be made to experiments in which a 3’s worsted and a 7 skeins woollen (both of similar diameter) were used. In the milling of both fabrics together, the texture made of the woollen yarn shrank fully 8% more than the worsted. Here,

the excess of shrinkage on the woollen was chiefly due to yarn structure,”

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Again, it does not necessarily follow that a dry state should permit felting equally with the wet. It must be remembered that the dry fibre is springy, i.e., ELASTIC, in the strict mechanical sense of showing a tendency to return to its original size and shape after deformation ; whereas in the wet state its elasticity is immensely reduced, it is almost a purely non-elastic plastic substance like, for example, artificial silk wetted-out. Hence, while fibre entanglement can occur and will be retained in the wetted state, this entanglement persist- ing during the drying, it does not follow that a similar degree of entanglement is possible in a dry fibre-mass. Any attempt to felt dry fibre by purely mechanical means—especially of an impulsive type, as in stock-milling—would simply result in excessive fibre breakage. Some further guidance as to the relative importance of serration-locking and fibre-interlacing in the felting process may be gained from the following illustration. Suppose that the short flocks from a cutting machine working on a clear finished worsted of a, fine merino quality are taken. This will vary from, say ;45 of an inch to mere dust. It will be agreed that as fibre for felting purposes such material would be almost valueless, being over short, even for the “‘ flocking ”’ fuller. Yet in a length of of an inch there must be on an average or at least forty serrations, sufficient, it would be thought, for considerable interlocking. The logical conclusion is that serration interlocking is a comparatively minor felting factor. As an example of strength gained by mere lapping or inter- lacing, the case of an ordinary rope of hemp, jute, or coir, etc.. may be considered. Such fibres are usually smooth-surfaced, possessing no serrations, but their mere spiral intermeshing is sufficient to produce great tensile strength in the assemblage. The friction of cords increases in high ratios with the amount of lapping, twisting, orentanglement. In acertain experiment, a cord was wrapped over a cylindrical block of wood ; it was weighted at one end by 1 lb., maintained constant; the weights required to set it in motion at the other end varied with the amount of lapping round the wooden cylinder, as follows :—

LAPS. WEIGHT TO START MOTION. 1 3.6 2 9.2 3 27.0

‘The enormous rate of increase of the friction is evident.

WHY WOOL DOES NOT FELT ON THE SHEEP’S BACK.

This question is relevant and instructive in the present connection ; there may be from 4500-5000 hairs per square inch, yet felting does not occur to any material extent, nor

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much in the baling of fleeces for transport. The supporters of _ the serration theory will reply that in this state the fibres, with their serrations, all pointing in one direction, present the least favourable condition for interlocking ; and that further, the wool yolk fills up the scales, lessens friction, and hinders mutual entanglement. The upholders of the adhesion hypo- thesis have no very adequate defence to this proposition ; the body temperature of the sheep roughly corresponds to that of the milling process, and the presence of the wool grease and suint should produce that plasticity and “‘ gelatinisation ’’ on which the theory depends. From the point of view of the third theory, that of fibre interlacing, this problem of the non-felting of the fleece wool offers no difficulty. The individual fibres are firmly attached by the roots, they grow outwards roughly normal to the surface and parallel to each other, and the presence of the wool yolk keeps the wool in a softened non-elastic state in which a permanent matting or inter- mixture is not possible. As a matter of fact, such little felting as occurs in natural wool favours this last hypothesis. Lamb’s wool exhibits more felting than sheared wool; evidently the finer points of the former permit readier entanglement of fibre than the blunt ends and thicker structure of the latter.

GENERAL CONCLUSIONS ON THE THEORY OF FELTING.

It thus appears probable that the matting together, inter- mingling and interlacing of the individual fibres while in a state of reduced elasticity due to moisture, heat, etc., is the principal factor in the milling process. From this follows the shrinkage of the yarns and finally of the fabric. The partial release of fibre from the yarn gives the “ cover ’”’ and handle ; and the interlocking gives that increase of strength which results from good milling. Serration interlocking is not necessarily excluded from participation, but the older view that it is the prime, if not the only cause, is certainly erroneous ; it can only play a minor part. Mere adhesion of fibre is probably almost non-operative in the ordinary milling processes. The mechanical aspects of the entangling of fibrous elements have received too little attention in researches upon the basis of felting. Consider, as an illustration, the stability problems presented by a pile of powdered cement—a medium entirely without bonding—and an ordinary haystack, a mass of fibres crossed in all planes. Cement may be so finely powdered that it will flow almost like a liquid; the grass stalks of the stack, by mere entanglement, form a structure stable to a height of 20 feet. The conditions of intermingling of fibres in a felted piece are on: similar lines. It must be remembered that in non-lubricated surfaces of solids the coefficients of friction are large, generally of the order of 4-;4,. The enormous increase

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in strength gained by even a few lappings of a rope round a support is a commonplace to engineers, who are well aware of the logarithmic law of friction applying in these cases. There is no need to assume special surface irregularities, such as teeth, barbs, serrations, etc., to obtain considerable resistance to relative motion among such masses of tangled fibre as are present in milled fabrics. Hemp, coir, and other rope materials, do not show such features; they are not presumed in the structure of ropes, nor even in the yarns and twists of the textile industry. The lateral contact of fibre surfaces and the known laws of solid friction are considered sufficient to account for the properties of the mass.

ILLUSTRATIVE EXPERIMENT. (Law.)

A length of condenser sliver was tested and registered nil. Then turns per inch were put in the same sliver :— With 5 turns per inch it registered a pull of 4.4 ozs, 29 7 29 9 9 8.5 9 29 9 2? 9 9 12.5 29 29 1] 29 9 99 17.4 >? While the soundness of the Interlacing Theory of Felting is not contradicted by any strong sum total of facts, it perhaps omits or neglects certain items of importance. One of these is the experimentally proved factor of ‘‘ creep,” i.e., the uni-directional motion of the fibre due to the serrations. It: is undoubtedly true that these should cause entanglement when by any external force there is a displacement of the fibre. In a milled piece the projecting fibres always have the skin end embedded in the cloth and the points free. In order to avoid over accentuating this into the importance of a Serration Theory of Milling, it must be noticed that the scales must certainly be most active when they are in the dry state ; and felting action is just as certainly most active when the fibre is in the swollen state, or when its rigidity is largely lost and it has become plastic. Another unexplained item is the rate of milling ; if this is properly measured by the shrinkage, it is certainly not a linear action. Some rough tests tend towards a parabolic form—or perhaps even exponential—for the time relation. In a paper on “ The Moisture Content of Wool,’ S. A.

Shorter has restated the position of the “scale theory ”’ as follows :—

‘‘ Let us consider a single fibré in the midst of other fibres, with which it is entangled at different points along its length. We may divide these entanglements into classes :— 1. Those which are so tight that no motion is possible. 2. Those in which there is sufficient freedom for the fibre to move relative to the entanglement in the direction of the root end, i.e., in the direction favoured by the serrations.

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If the fibre has along its length entanglements of the second class only, casual disturbances will cause it to travel as a whole through the fabric, just as a barley awn started the right way round will travel up a person’s sleeve. This state of affairs, though by no means infrequent among the short fibres of a woollen fabric, will, however, be exceptional. In general, a fibre will have entanglements of both classes—it will be held tightly at certain places and free to creep at others. Let us now consider the case of a fibre which has an en- tanglement of class (1) at one place and one of class (2) at another. For convenience we will refer to these as a ‘place of complete entanglement’ and a ‘place of partial entanglement’ respectively. ‘There are two cases, (a) where the scales on the portion of fibre between entanglements point towards the place of complete entanglement, (6) where the scales point towards the place of partial entanglement. In case (a) casual disturbances will tend to cause the fibre to creep so as to diminish the length between the entanglements. This length of fibre will therefore tend to tighten up automatically. Any temporary deformation of the fabric which brings the two entangle- ments closer together will allow further creeping to occur, so that when the external force producing the deformation is removed, the two entanglements will not separate to quite their original distance. There is thus a permanent local consolidation of the fabric. Let us now consider case (b). In this case casual disturbance will lead to an increase of the length of fibre between the two entanglements. If the fibre were a rigid rod, this would tend to produce a local expansion of the fabric. Owing, however, to the lack of appreciable flexural rigidity of the fibre, it merely loops and ultimately becomes entangled with other fibres.

There are therefore two fundamental factors in milling :—

1. Undirectional freedom of motion due to the serrations on the fibre. 2. Lack of appreciable flexural rigidity of the fibre.

The action of moisture and milling is to produce conditions of fibre contact favouring the operation of the first factor. The looping action which occurs in case (6) will undoubtedly contribute indirectly to the milling effect by adding to the complexity of the fibre arrangement, but it cannot be regarded as exerting direct fabric consolidating action.”’

i EFFECT OF SERRATIONS IN) MILLING Csronter) A\l- PLACE OF TOTAL ENTANCLEMENT

B:~ PLACE OF PARTIAL ENTANCLEMENT

I Fic. 69.

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This theory differs from the classical *‘ interlocking scales ”’ theory in two respects. In the first it postulates unidirectional freedom not absolute fixity as the characteristic effect pro- duced by the scales. Secondly, this unidirectional freedom involves the scales on the ENTANGLED fibre, not those on the ENTANGLING fibres. This point is well illustrated by an observation of Ditzel, who found that fibres enclosed in a cotton wrapper could actually be milled into the material of the wrapper. The characteristic swelling of colloid substances under the influence of heat, moisture, or special reagents, is a general factor in the felting process. In this state the wool fibre is particularly sensitive, somewhat resembling in its plastic and amenable condition the annealing effect on steel. For example, in the blowing operation under the combined heat and moisture of the steam, the fabric under slight tension sets the weave in a regular and definite manner which is made permanent by the subsequent cooling off and drying; and under similar agencies even embossing effects may be impressed on wool. It follows therefore that the complicated interlacings of the fulling process will be facilitated by all factors tending to bring about the turgescent condition. Experiments have shown that wool may be milled in quite diverse liquids, caustic alkalies, soap solutions, and dilute acids ; a phenomenon quite precluding specific chemical effects, but perfectly rational from the turgescent colloid standpoint. There may be distinctive results obtainable by particular liquids—thus Nitrate of Mercury is used in the hat industry on fur—but the fact remains that the production of the turgescence is the essential condition. This general statement may therefore be applied to determine the advantages or otherwise of certain methods, devices, or materials operating in the milling stage of cloth finishing. Thus, the employment of fuller’s earth in cloth-milling can only have a detergent utility, contributing nothing directly to milling per se; and the questions of hard soaps v. soft soaps, acid v. soap milling, use of alkalies, or milling in the grease, must be judged in the first instance from this standpoint. Temperature is an important element in the development of the turgescent state, and it would be expected that the fulling process will be greatly affected by variations of temperature. It is a fact of common experience that colloid bodies which at low temperatures simply swell up by absorption of water, e.g., gums, gelatine, etc., by slight heating become viscous liquids. It is an old device to introduce a steam pipe into a milling machine, and the difference between summer and winter milling is familiar to all practical fullers. The enclosure of the roller miller is a technical application of this temperature

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effect ; with some wools and fabrics there may be over rapid shrinkage, and it is desirable to open the top of the machine casing. If pieces are milled from the cold and allowed to develop their own temperature by the heating effect of friction, it will be found that the temperature and best speed of milling are dependent ; there is evidently an optimum temperature for the fulling of wool in the neighbourhood of 40°C., or slightly over. At higher or lower temperatures the speed of milling is lowered, irrespective of the nature of the liquid medium employed. This temperature roughly approximates to the body temperature of the wool as it grows in the fleece. It is a fact of ordinary practice that wool absorbs liquid water with evolution of heat, e.g., in the crabbing process, and in dewing.

IMBITION CURVE FOR

CELATINE WATER [wwrayior Wts I

Ts

Fig. 70.

Comparatively little investigation has been devoted to the theoretical principles of imbibition and of turgescence in the case of the wool fibre, but much work has been done upon the related colloid :—Gelatine ; some of the results probably hold good by analogy. A paper by J. A. Wilson on the ‘‘ Imbibition of Gels ” (Third Report on Colloid Chemistry), will be found informative :— ‘In gelatine, the rate of swelling noticeably decreases, the volume tending to approach a definite limit; the absorbed water behaves much as though it were dissolved in the gelatine and it can be removed by treating with absolute alcohol, the volume of the gelatine diminishing. Some heat is evolved during swelling, perhaps indicat- ing a loose chemical combination. The degree of the swelling is dependent upon the previous history of the gelatine. Gelatine swells

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to a much greater extent in dilute acids than in water, and also in alkalies; neutral salts hinder this swelling. Thus the parts of solution absorbed by one part of a certain sample of gelatine at 18°C. were in pure water 8, in 0.006 normal hydrochloric acid 42, in 0.05 N HC1 28, in 0.3 N HCl only 17. These results have an intimate bearing upon the absorption and removal of Sulphuric Acid by wool. Collagen, fibrin, and other proteins behave much like gelatine when immersed in solutions of acids, alkalies, or salts. The theory of Tolman and Stearn assumes that, because of their amphoteric nature, protein colloids have marked tendencies to adsorb hydrion from acid solutions and hydroxion from alkaline solutions.”’ .

The absorption of acid from dilute acid solutions by sus- pended particles of Casein takes place in accordance with the equation x = K t™, no soluble compound being;formed or

BOTANY TOP

LONG WOOL TOP CROSS

TIME MOISTURE CURVES OF WOOL. IN ENGLOSURE-1I00 AC. HUMIDITY.

[RRADFORD CONDITIONING HOUSE E.TOWNSEND]

ra;

being retained within the colloid particles. The velocity of solution dx/dt = Km t™ + yields a constant “* Km,” termed by Robertson the Coefficient of Penetration. A wool fibre probably resembles an osmometer with a membrane easily permeable to crystalloids but little to colloids. But actual chemical hydration may play a part; proteins which really dissolve are known to become hydrated in the process, the thermal phenomena confirming this result. There may be chemical binding of the water and also swelling by direct osmotic imbibition.

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“If two gelatine plates be brought to the same degree of swelling, the one in neutral and the other in acid water, and if they be then immersed in absolute alcohol, the alcohol will abstract all of the water from the former but not from the plate swollen in acid water. Now the fact that a constituent of a system can be completely removed from it by washing out with an appropriate solvent affords no valid proof that the constituent in question did not exist within the system in a state of chemical combination. But if, on the contrary, it should prove impossible or exceptionally difficult to remove the constituent by washing with a fluid in which it is very soluble, then the prima facie evidence that it exists in the system in a state of chemical combination is very strong. We may conclude, therefore, that when gelatine is swollen in acid water, a part of the water is chemically bound by it.’’ (Robertson.) If similar phenomena obtain in the case of Keratin or wool substance, there are obvious deductions applicable to the acid dyebath, acid milling, carbonising and the related operations of practice. 7

CHLORINE AND WOOL FELTING.

The particular action of chlorine has already been referred to, and supporters of the serration theory have regarded the scale-erosion and loss of shrinking power as an “* experimentum crucis ’’ in their favour. Quoting again from Dr. Woodhead’s paper :— “Several samples of wool have been treated with various strengths of an acid solution of hypochlorite. The first microscope contains a few untreated fibres which show the typical scales, the rest show a series treated respectively with 5%, 10%, 15%, 20%, and 30% solutions. From these we see that as we increase the strength of the solution the scales gradually lose their sharpness, become more and more indistinct, exceedingly difficult to detect, and finally the fibre tends to break up. A large number of comparative tests have been made in conjunction with Mr. Lodge with chlorinated cloth on these lines, and we find that as the strength of the solution is gradually increased, the cloth loses its shrinking properties ; and that when the scales have lost their gripping power the cloth is for all practical purposes unshrinkable.”’

Now it must not be overlooked that chlorine—whether applied as Bleaching Powder Solution, Sodium Hypochlorite, Chlorine water, or as gaseous chlorine—has an extremely vigorous action on wool; as much as 30% by weight may be taken up, but the wool will then have lost all its characteristics and is disintegrated. The chemical action concerned is not understood, perhaps there is an extended formation of the chloramines. Physically the wool is harsher, and possesses scroop ; it wets easily, but—and this is very important in the present connection—is less turgescent. It has probably lost much of its colloidal nature. It does not therefore follow that the diminution of felting power is necessarily dtie to erosion of the scales ; chlorine causes a general degradation of the wool substance. The combination of chlorine and wool substance hiberates heat, and leads to the development of acid properties in the wool.

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290 SPECIAL EFFECTS OF MILLING.

An interesting example of special milling is seen in the case of ‘‘ boucle ”’ cloths, i.e., fabrics whose surface is covered by a mass of curls or boucles. In these cloths the warp is formed of a compound yarn of wool of long staple but poor milling properties, having twisted round each thread a finer thread of good milling wool. In the milling process the felting of the latter draws up the former, bursting out on the face of the cloth into small knops or boucles. Such compounds—loop or curly yarns—are made in various ways. If a woollen is twisted with a mohair yarn, this latter being delivered at a greater speed, during the milling process the wool felts; the mohair is much less felting and consequently comes to the surface in loops. An astrachan may be successfully imitated by a combination of cotton warp and mohair weft, weaving the bulk of the pick plain and then allowing it to float for about 1 inch ; in the milling the floating portion forms surface curls. Or cotton warp with a highly felting Saxony weft may be employed.

The Manufacture of Felted Fabrics.

The principles of milling are particularly well exemplified in the manufacture of felts, i.e., fabrics produced direct from the fibre without the construction of yarns, and therefore also without a weaving operation. Historically, the earliest fabrics were produced by a simple felting process, but the advent of power carding, with its increased facilities for producing continuous sheets of fibres, led to enormous development. Felted fabrics are of two main types :—

1. Those produced from sheets of carded wools, etc., by purely felting methods; these are true felts, e.g., saddle cloths, carpet and hat felts, etc. 2. Those produced by the milling of fabrics composed of spun and woven yarns, e.g., printing blankets, etc. Felts of this type follow the routine applicable to the milling of woven cloths generally.

In the pure felting methods applied to the first class, a “batting ’’? frame follows the carder; the sheet of fibres is delivered on to an endless band vi 50 yards or upwards, and with other layers to the estimated amount forms the “ batt.” By damping, steaming, and pressure, this is consolidated or ‘‘ hardened ”’ into a material capable of undergoing the ordinary fulling treatment by the stocks or roller milling machine. The hardening machines are either “ flat or table ” or “*‘ roller ”’ types. The latter consists of about twenty lower metal rollers, of which about half-a-dozen are of copper and heated by steam. Above this series are placed nineteen wooden rollers,

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and these are capable of some lateral sliding. It is evident that the conditions for turgescence and interlacing are fulfilled. In the flat system, a double table having upper and lower surfaces and capable of some lateral traverse of the upper section operates upon a few feet of the batt at a time. The after processes follow the lines of ordinary milling by stocks, roller machines, or variations and combinations of these.

Waa \ Weg Ah) Ah 4

© 4 ee ee = = = OE. ee re lh OO

= 3. —

Fie. 73.—BaTtrina FRAME.

Applications of the Theory.

In the ‘“‘ Finishing of Textile Fabrics,’’ Prof. Beaumont has published a very complete series of experiments illustrating the effects of the different variables entering into the milling problem. Among such factors are :— 1. Fibre characters, e.g., serrations, waves, staple, diameter. 2. Physical properties of fibre, i.e., density, elasticity, tenacity. Yarn structure ; worsted or woollen type; amount of twine ; multiple yarns. Nature of fibres ; use of cotton, silk, recovered wool, etc. Fabric structure ; density of warp and weft, nature of weave, multiple cloths.

ee

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These relate to the materials on which the milling process is exercised, but there are also operational factors, such as :— 1. Temperature. 2. Moisture, detergents, special reagents. 3. Mechanical: pressure; surface friction; effects of impulse; ‘‘drag’” or ‘“‘throttling’’; alteration of stresses ; tension; variation of line of travel, etc.

eas

see as

Fie. 74.—FELT SCOURING MACHINE. (Wm. WuItELEY & Sons Ltp., Lockwoop, HUDDERSFIELD. )

It is quite possible, as is the case with all sound hypotheses, to predict from the Interlacing Theory the consequences of certain factors or special conditions which may obtain in the

milling operation, and a number of such cases will now be considered.

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293 RECOVERED WOOLS IN MILLING.

Strictly speaking, the term “ shoddy ”’ should be restricted to wool recovered from un-milled fabrics, e.g., worsteds, while ”’ is fibre obtained from milled goods, tweeds, flannels, blankets, ete. It is obvious that wool which has passed through the range of finishing operations—it is said that wool may be recovered half-a-dozen times over—cannot exhibit the pristine properties of the natural fleece. Nearly all the finishing processes weaken the strength of the fibre: heating, by crabbing and blowing, affects it chemically ; the mechanical effects of scouring, milling, pressing, etc., distort it, and the scales suffer erosion ; a general reduction of staple occurs by breakages ; and the wear and exposure in its use as a garment alter it—evidently by some unknown chemical degradation— resulting in the effect commonly known as “fading.” Re- dyeing, with or without re-mordanting, further deteriorates the material. In yarn dyeing it is not uncommon to find that the dyeing process diminishes the yardage per pound some 20%, and the tensile strength 10°. Prof. Eber Midgley, in a lecture on the “ Influence of Dyeing and Finishing on Woven gives an experimental table relating to a cloth, finished vicuna, as follows :—

INFLUENCE OF FINISHING PROCESS ON TENSILE STRENGTH.

WARP WAY WEFT WAY MEAN. STRAIN. STRAIN. STRAIN.

1. Grey cloth 133 93 113 2. After Crabbing. 128 80 104 3. 5, scouring 122 72 97 4. ,» Milling . 130 67 98 5. ,» Raising & Cutting 125 65 95 6. ,» Dyeing & Tentering 129 69 99 =: , Cutting & Brushing 126 67 96 8. ,, Dressing 129 67 98 9. Permanent Finishing 123 65 94

Each result is an average of twenty tests.

The net effect of all this, with possibly several repetitions in the case of recovered wools, is to diminish the milling properties very seriously. Every practical fuller is familiar with the phenomenon of pieces refusing to mill up to the required shrinkage even when all the operational conditions are apparently fulfilled, and all degrees of imperfect milling up to this extreme may occur. In this connection the practice of “feeding ”’ a cloth in milling by adding flocks may be mentioned ; such flocks are commonly recovered wool, and their scanty hold on the skeleton of the fabric is often painfully evident in the subsequent washing-off operation.

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Roberts Beaumont cites an experiment contrasting Tas- manian wool and a waste of similar quality ; the pure wool felted quicker, further, and would have continued to mill longer if the experiment had been extended. Carbonised wool, it is stated, takes longer and does not mill _so far as the non-carbonised fibre. . Some further tests are here quoted from the research of Mr. H. Wilkinson and Mr. W. Law :—

GREASY SCOURED MILLED CLOTH. CLOTH. CLOTH. Warp. Weit. Warp Weft. Warp. Weft. Actual Strength 100% 100% 89 83/2 111 65/2 Calculated strength

after milling, allow-

ing for increased Warp. Weft. Warp. Weft. ends and picks 103 108. lap iz A heavily-milled worsted army fabric gave :— CALCULATED STRENGTH OF STRENGTH AFTER ACTUAL STRENGTH GREASY CLOTH. MILLING, ALLOWING OF FOR INCREASE IN FINISHED CLOTH. ENDS AND PICKS. Warp. Weft. Warp. Weft. Warp. Weft. 100 100 124 114 99 81 And comparison of qualities is given by :— CALCULATED STRENGTH scape Sane OF MILLING, ee GREASY ALLOWING FINISHED CLOTH. FOR INCREASED

CLOTH. ENDS AND PICKS.

7 Warp. Weft. Warp. Weft. Warp. Weft. Saxony Woollen 100 100 123 109 84 64

Crossbred Worsted 100 100 110 115 oo. 78

Results from single thread tests gave the following, the treatment being performed on the hank :—

AVERAGE STRENGTH CONDITION OF YARN. FOR SINGLE PERCENTAGE THREAD. STRENGTH. (IN OZS.). 1. Greasy Yarn 11.5 100% 2. Degreased (petrol. ether) 1] 95.8 3. Scoured with soap, as for piece scouring 10.2 88.5 4. Scoured with Soda, 8° Tw. 8.6 74.8 5. Worked 5 mins. in water at 120° Fah. 8.7 75.6

Messrs. Law and Wilkinson summarise their results as :— 1. The removal of the grease does not in itself seriously affect the strength of the fabric.

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2. The scouring of yarns under conditions such as obtain in the washing and milling of cloth decreases consider- ably the tensile strength of the yarn ; judging from the smaller loss in worsted as compared with woollen yarn, it is largely due to mechanical disturbance. 3. Calculated on the basis of the strength per thread in warp or weft, a milled fabric is weaker than the greasy cloth as taken from the loom ; the loss may more than balance the gain due to shrinkage. 4. Loss in strength occurs much before the flocking stage. The factor of ‘“‘ mechanical disturbance ’”’ in (2) above is probably the reason why yarns and fabrics alike usually show a slight diminution in tensile strength after processes involving mere steeping only, e.g , degreasing, scouring without working, etc. What evidently occurs is a small amount of release of. inter-lapping of fibres, with slackening of lateral contact friction, and consequent falling off in strength. The engineer’s Law of Rope Friction, viz., that the friction varies logarith- mically with the amount of lapping, is evidently capable of application to fibres in yarns, to twisting of yarns, and to intersections of yarns as warp and weft in fabrics. Some even roughly approximaté measurements of the coefficients of friction of wool on wool, dry, water-wet, soap-wet, oiled, etc., would probably help to clear up some minor points in tests, or even works’ practice.

COMPLEXITY OF STRUCTURE.

Intermingling of the fibre elements and consequent shrinkage in the yarn and the texture is obviously promoted by all departures from simplicity of structure ; and this general law applies to both yarns and weaves. The parallelism of worsted threads and the intercrossings of fibre in the woollen thread have already been noted. Single yarns felt better than multiple, and hard-spun yarn felts less readily than soft-spun, whatever the type of yarn and kind of wool. Similarly, when yarns are built as warp and weft into fabrics, the same general law holds good, i.e., complexity favours felting. Among weaves, the plain weave mills least, and then the simpler twills, the frequency of intersections of warp and weft being the dominant factor. For certain milling effects standard weaves are adopted. Thus an unshrinkable flannel should be woven plain. Knitted as against woven fabrics are notorious for rapid felting and shrinkage.

Milling and Fabric Strength.

It is an experimental fact that the tensile strength of a fabric is greater than the sum of the strengths of the individual fibres, at any rate in firmly built cloths ; probably, as in the

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case of twist in yarns, because of increased lateral contact and friction. In experiments previously cited (Prof. Midgley, p. 253), it has been seen that nearly all the finishing operations diminish the fabric strength. The Milling Process is com- plicated in this respect by the shrinkage of the cloth, and the increased density of threads per inch.

N.B.—A similar remark applies to scouring where felting takes place.

Much of the following illustrative matter is taken from a lecture by Mr. W. Law, of the Leeds University Textile Department, on the * Influence of Scouring and Milling on a Woollen Fabric ” :—

“Taking the greasy test as representing 100% strength in warp and weft, a scoured cloth was found to yield 83% in the warp and 67.4% in the weft. This is not a uncommon type of result in ordinary scouring, and is due to the mechanical action of the rollers being more severe on threads lying transversely to the line of motion, e.g., weft ;. such threads suffer more diverse stresses of a torsional, etc., kind. Now in milling also, losses of real strength, to be carefully distinguished from strength gained by increased density and felting, are invariable. The milling brings the ends and picks closer together, and if the cloth is set 112 ins. wide and milled up to 56 ins., the ends per inch are increased 100%. If the yarn loses 50% of its strength, then, twice the number of ends being tested, the same total strength will be registered in each case. An experiment was tried with yarn which registered 24.1 ozs. ; it was woven into a cloth with 28 ends and picks per inch; a 63 ins. wide pattern containing 199 threads was tested and found to give a breaking load of 375 lbs. Calculation would give 1/16 of 199 times 24.1 or 300 lbs., so that the actual gain is 75 lbs., an increase of approximately 25%. cloth, subjected to milling and tested at various stages, gave the following results :—

THREADS BREAKING PER INCH. STAGE OF STRAIN IN LBS. I —— FINISHING. ners — WARP. I WEFT. WARP. I WEFT. 199 189 Greasy 375 372 209 194 Scoured 342 257 230 192 Ist Milling 347 272 241 201 a 365 245 261 204 ams. 390 225 283 214 the 440) 257 298 216 Gth::... 475 247 314 223 ae 517 242

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An examination of these figures show that the third stage of milling is reached before an equal strength of warp is registered, and as there are 199 ends in the greasy cloth and 261 ends in the milled

cloth, it takes 261 ends milled to give the same strength as 199 ends in the grease.

If the cloth had lost no strength during the operation of milling, the strength in the milled cloth should have been 199 ; 261: : 375: 512 instead of which it was only 390 lbs., or a loss of 24% from the greasy to this stage of milling. In other words, we have, as the sett was 28 per inch in the loom, 39 per inch in the milled cloth. For every 100 ins. of finished cloth we would require 100 x 39 = 28 140 ins. of greasy cloth before we could register the same strength, showing that the strength of 62 ends has been completely lost.

It will be noticed that in the warp direction after this point that there is a gradual increase in strength by further milling, the reason being a gradual increase in the ends per inch, due to the shrinkage by milling, but if the weft be examined it will be seen that at no point does the milled cloth equal the strength of the greasy, this is due to two causes :— (a) The milling in the weft direction was not so much as in the warp. (6) The damage done to the weft was greater than that done to the warp. It may be of interest to compare the greasy and 6th milled tests of the weft. In the greasy there are 189 picks, while in the milled there are 223, but the cloth is considerably weaker. The reason for this greater loss in the weft direction is that there is the same injurious action as in scouring, and the milling process so far as strength is concerned is a damaging one from start to finish.

Although the figures show a weakening of the fabric, the yarns tested from the several cloths show a gradual decrease in strength from start to finish, due largely to the action of the rollers in the machine.

If the strength of the greasy yarn taken from the fabric equals 24 ozs. and the strength of the yarn taken from the 6th period of milling 11 ozs., this shows a depreciation in yarn strength value of 24:13::100:x = 54% in the warp. x = 66% in the weft. This very serious loss in strength is not revealed in the cloth because of the shrinkage, which may be seen by comparing the ends per inch (a) in the greasy cloth, (6) in the milled cloth. Also the sett increases as the cloth is milled, and from previous observations we have noticed that setting gives support, and therefore adds strength.”

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Acid Milling.

Reference has already been made to the fact that the felting of wool may take place in various media, differing as widely as the electrolytes, caustic alkali, sulphuric acid, etc., on the one hand, and the colloid solutions of soap on the other. It has also been emphasised that this disposes of any special chemical action such as is required, for example, in some parts of the scouring process. Milling will proceed, but only slowly, in pure water ; it is accelerated by warm water. This generality in the media possible in the milling operation has led to the superficial conclusion that the liquid acts merely as a lubricant, diminishing the fibre-to-fibre friction of the yarn, and also the piece friction in the machine. If this were correct, then ordinary lubrication with oils would be possible in the felting process ; but oiled wool and oiled yarn exhibit no felting-up tendencies. The so-called method of ‘* Cloth Milling in the Grease,”’ is carried out by first wetting the pieces in alkali ; the goods treated in this way usually carry heavy oiling containing free fatty acids ; there is abundant soap formation and lathering; and apart from its extremely dirty nature, the method is essentially soap-milling. It would be an interesting scientific experiment—and one may hazard the prophecy that the result would be negative—to attempt .a milling experiment in glycerine. The inference, therefore, that the liquid medium in milling has merely a lubricating function, is not warranted; the evidence points to the necessity for establishing a state of turgescence in the fibre. Now theory and practice show that this can be brought about by various solutions, the relative advantages of which depend on the circumstances involved. The time-honoured method of milling with soap solutions has theoretically no absolute superiority ; and in particular, acid milling has for certain conditions special merits. It has long been practiced in the Hat Felt industry, and was in practical working in Germany on piece goods more than twenty years ago. Very little published information exists on Acid Milling. Mr. W. Harrison, M.Sc., conducted some experimental work for the Wool Research Association, but the principal source is a practical and informative lecture by Mr. Shelley Begg, before the Society of Dyers and Colourists, and reported in their Journal of February, 1920. Almost the whole of the matter which follows is due to Mr. Begg. The materials are scoured in a similar way to that employed in soap milling—omitting the soaping-up for milling—and washing all soaps away completely. The scouring machine is half filled with water, the door is closed, and the water is retained in the box.

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For each 100 lbs. weight of cloth 3 lbs. of B.O.V. or 2 Ibs. of D.O.V. are poured into a lead-lined cistern, and flows through a half-inch lead pipe to the middle of a box, which should contain sufficient water for the bottom roller to rotate in and mix the acid and water. The door is raised and the acid water allowed to flow on to the material in the machine. The cloth is allowed to run 15 minutes longer for the acid to be taken up, the acid water is run away, and the material washed with a copious supply of water for 15 minutes. After hydro- extracting, the pieces are ready for the milling process. No liquid is required at the commencement, but with heavy milling a small amount of water is necessary to replace that evaporated during the process. This amount is left to the judgment of the attendant or workmen, which is only gained by long experience, both in this and other methods of milling.

With regard to strength, the results of tests were as follows :—

TENSILE ELONGA- STRENGTH. TION, lbs. ins. Acid milled 290 2.50 Soap-milled afterextracting 242 2.37 i without _,, 255 2.68 Grease milled 242 2.31

The warp and weft tests were practically in the same ratio. Advantages of Acid Milling compared with Soap Milling :— 1. The scouring and milling plant can be run all day. 2. The dyes are fixed and there is no necessity to hurry the operation. 3. Acid dyes can be used for even heavy milled goods. 4. The goods are milled quicker than with soap. 5. There is less loss of weight compared with either soap or grease milling.

6. Higher temperatures can be used without certain colours bleeding. 7. No after-scouring is required. 8. More distinct colours are produced. 9. There is less handling, and therefore economy of labour. 10. There is a great saving of soap ; and 11. A considerable saving of water. (All practical scourers

know the difficulty of removing soap from soap-milled fabrics.) 12. The cost of upkeep of plant is reduced. 13. Less weight is required on the lid of the machine ; and 14. Less power is required to drive the machine. 15. The material can be allowed to remain wet overnight or over the week-end without colours bleeding.

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RETURN PER WEEK OF 100 Preckes oF 112 LBS. WEIGHT.

NUMBER OF PIECES. OF PIECES weir: DRY WEIGHT, Twice Total Once Handling. Weight. Handling.

ewts. ewts. ewts. tons. tons.

Unloaded from scouring machine 100 300 600 : 30 15 Loaded into hydro extractor Se 100 300 600 30 15 Cuttled from hydro extractor 100 200 £06 20 10 Unloading from milling machine .. 100 200 — 10 10

gia eg of tons handled in soap a Take 50 weeks per year—40 x 50 = 2,000 tons per year. Say four men are Total ae of tons handled in acid 50 employed i in the milling department—2,000 ming Ps <% eg — 4 = 500 tons per man to handle with

the acid process.

I eae na go ae

300

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COMPARATIVE TEST

on 334 ozs. Kuaxkt Greatcoar Actbp AND Soap MILLED.

Grease Weight.

Width before Milling.

Length before Milling.

Method.

Type of Machine.

Width after Milling.

Time

Length after Milling.

Per- centage Loss.

Clean Dry Weight.

Ibs. 144

142

GoD

148

=

146

ins. 74

74 74 74

yas. 72

72 oe

72

Scap Acid Soap Acid

64-in. rollers single

24 99

Tandem 4

hrs. ins, 54 55

+ 55

OY

oa

55

rice =

55

yds. 55

55 55. 505

ibs. 102.25 20

L072 104.33 I 29.5

1J1.6 23.5

301

STRENGTH AND ELASTICITY OF THE CLEAN Dry CLOTH BEFORE CONDITIONING.

Method. Tensile Strength Warp. Elasticity Warp. Tensile Strength Weft. Elasticity Weft

lbs. ins. lbs. ims.

Acid milled 360 =. 90 380 30

Soap milled 3 338 21 365 31

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Any discussion or criticism of acid milling must turn on minor details only ; the process is well established both in principle and practice, and was extensively used in the late War, the heavily-milled, acid-dyed, military fabrics being peculiarly adapted to this system. It is essential that the preliminary acidification of the pieces is carried out separately ; the practice of soaping in the milling machine itself cannot be imitated in the acid process. Wool absorbs Sulphuric Acid readily (Cf. section on Acids and Alkalies), the 15 minutes’ rinsing-off in clean water ensures uniformity in the absorption. The cloth after milling is finally left in an acid condition, as against the alkalinity resulting from soap-milling. This favours brightness in black-and-whites, etc., acting as a partial bleach. (See Chapter II.) Acid-milled cloths well soaked in water show Sulphuric Acid by the Barium Chloride reaction. Having regard to the enormous use of acid dyeings on wool, the advantage of acid milling in this respect is very great.

There is some difference of opinion as to the effect of the method on the handle and softness of the fabric, and it appears rather probable that some slight harshening of fibre takes place; the class of goods on which the method has been mainly employed, e.g., heavy woollens, does not test this point very well, especially when heavily raised, e.g., railway rugs ; whether the process would be as well adapted to, say, a fine quality white flannel, or stock milling of worsteds, is more questionable.

There are important works’ advantages in this system; it is stated that there is a complete absence of mill-rigs ; there is marked economy, both in labour and material, over soap- milling. There is further great freedom from moulds, mildews, etc. ; the alkaline condition is favourable to bacterial actions, while acids are well-known to be antiseptic. While, of course, Sulphuric is the cheapest, other acids, e.g., Formic, Acetic, etc., may be employed ; in certain cases where colours like Congo Red sensitive to vitriol occur, these alternatives are useful. The quantities given, viz., 2% D.O.V., on the weight of material are not indicative of the actual acid content of the cloth as milled ; owing to the rinsing-off and whizzing after acidification, this will be somewhat indeterminate. Mr. Harrison’s laboratory trials indicated that up to an acid concentration of 4.9% the amount of milling was increased, decreasing after 19.6%. As the dilution is not given in Mr. Begg’s working, the concentration cannot be compared.

Another obscurity exists with regard to acid milling of goods containing cotton, especially as the after-scouring operation is dispensed with. It is generally asserted that

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subsequent drying processes, tentering, etc., by concentrating the remanent acid, cause tendering of the cotton. In any case, the cotton fibre does not absorb or retain Sulphuric acid with the avidity of wool, and the rinsing and hydro-extracting operations must reduce this danger to small proportions. A condition resembling the one under discussion results from the sulphur bleaching of union cloths, e.g., gabardines, etc., and experience has shown that careful working will eliminate any dangers.

It would be expected that a process of this nature, involving the employment of strong acids, movement of heavy pieces, and weighty machinery absorbing much mechanical power, would result in frequent stains in the cloth, and rapid de- terioration of plant. It is claimed, on the contrary, that defective goods are rare; and that depreciation is reduced as against the orthodox system of soap-milling. Plant can be specially designed against acid corrosion. (See chapter on Textile Cleanliness.)

The Practical Routine of Milling.

The present section is based upon the method of soap-milling, this being the standard system of the industry ; most of the manipulative detail applies, with little modification, directly to other methods.

6

Except when milled in the “ pieces will be passed through the usual preliminary operations of grey-perching, scouring, and wringing or hydro-extracting ; the scouring will include washing-off and lathering-up for milling.

Alternatively, if for grease-milling, the pieces will be wetted- out with alkali—soda-ash of 6—7°Tw. solution, by passage through a “‘ Lecker.’”’ This necessitates the use of a spinning oil containing free fatty acids, which, combining with the alkali in a process of saponification, forms the milling medium. The process is essentially soap-milling ; it is extremely dirty in operation, abundant flock and soap-sludge being formed, and is of course unfitted for goods intended for a high finish. Special machines should be reserved for grease-milling, and not used for goods on which a high standard of brightness, lustre, and finish is desired.

STITCHING.

The practice of stitching up the lists, or “ bagging,’’ face side innermost, of pieces for milling, is strongly recommended. The great dangers of chafing and mill-rigging are almosé

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304

a . IR

———— SS.

re

I

Fie. 75.—BAGGING or LISTING MACHINE.

(WM. BircoH, MAKERS, SALFORD.)

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305

entirely prevented by this means, and also the development of uneven or curled selvedges. If the face of the cloth forms the inside of the bag, it will be found that the resulting “* cover ’ is of superior character. The enclosure formed by the stitching causes a slight ballooning during the run, which, bringing about variations in the travel, checks all tendency to the formation of crimps. Machine stitching is quick, cheap, and worth while.

ENTERING THE CLOTH.

In roller milling the end of the piece is now bunched, put through the mouth-piece, and passed into the grip of the rollers: the machine is set into motion until the end has reached the bottom of the machine; this end is now pulled outside the door for a yard or two, and the rest of the piece run through till it lies in folds in the machine, leaving enough to sew to the front end; thus an endless band is formed. A similar process is followed with the remaining pieces, each passing through its own aperture in the draft-board. These apertures have various forms, circular holes, rectangular slots, etc., and are made in wood or metal, often brass. In the latter case, they should be watched for soap corrosion, and resulting copper stains.

MEASURING OFF.

Before the pieces are started up, a standard length, say 60-72 inches, is marked off along the list by two knots or strings to. serve as an index of the shrinkage, and hence the felting. The fuller will usually have a finished pattern of the fabric and instructions regarding the finished length and width ; and when flocks are to be fed into the cloth, the weight per yard.

MACHINE ADJUSTMENTS.

In the case of the milling department changing on to different fabrics, the first run or two is always tentative and experimental ; much adjustment and supervision is necessary in these trials. The distance between the rollers, the close fitting of the spout, even the opening and closing of the door to govern the temperature—all these are variables, the sum- total of which determines the final result. Small differences of routine or altered details have often a remarkable effect in milling. It is, for example, a useful device to insert rubber blocks about one inch thick under the springs and the spout- weights, thus preventing hard blows or shocks as the parts rise and fall. Apart from the elimination of noise, it is probable

U

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that incipient crimping is obviated ; it is more than likely that rigs start in the first instance from a localised shock. No text-book instructions can teach a miller the mode of adjusting the machines ; experience, with the free use of the method of trial and error, is the essential requirement. The miller will chalk up on the door of the machine the time of starting the run; after a few runs on a particular class of goods of the same milling qualities, the mere observation of

ff.

4 7 QQ SS

SPOUT TOP WEIGHTS FLANGES MOUTH PIECE DRAFT BOARD DRAG ROD

Fia. 76.—-ROLLER MILLING MACHINE.

time and the occasional handling of the goods to gauge the development of cover will enable the operator to dispense with the actual measurement of shrinkage. Until this stage is attained the machine must occasionally be stopped, the marked standard length found and remeasured, together with the width, and the progress of the milling thus determined. From these observations, the appropriate adjustments of the machine will be made.

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This presupposes a knowledge of the functions exercised by the different parts of the Rotary Miller, a matter which will now be considered. Whereas in the Stocks, the felting up in warp and weft is simultaneous and on the whole more uniform than in the Roller Miller, in the latter different parts of the machine separately produce these effects. In the draft-board, vertical rollers, mouth-piece, and between the main rollers, the

Fie. 77.—MILLING MACHINE.

(JAMES BAILEY, SLAITHWAITE, HUDDERSFIELD.)

pressure is transverse, and therefore promotes felting of the weft ; in all this portion, the warp or length of the piece is under slight tension due to the pull of the rollers. After passage through the rollers into the spout, compression length- ways of the piece begins, being governed by the weighting of the lid ; hence warp felting occurs in this stage.

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SHRINKAGE.

Felting and Shrinkage are not strictly proportional. A closely-set cloth felts well, particularly on the surface, and yet does not contract fully ; over loose spacing will allow excessive shrinking without corresponding felting. The progress of the felting in the cloth is judged :—(1) by the shrinkage as measured in the standard length and width ; (2) by the cover. During milling, the pieces warm up and tend to dry ; they should be sprinkled with warm water or dilute soap solution. With the heavier cloths, milling must not proceed too fast, as the outer layers felt up and to some extent protect the interior. If shrinking does not proceed fast enough in length, the lid of the spout must be further weighted, or the rollers slackened. If the width mills too slowly, tighten down the springs on the upper roller; in both cases, a little adjustment at a time. Cloths which mill too quickly in length may be doubled in the machine, and light-weight cloths may be run in parallel, i.e., side-by-side, to get a proper width pressure. If cloths take too long in milling, they should be taken out, the ends reversed, and when they have run about half-an-hour, shaken out thoroughly from end to end. Undyed wool mills more easily than dyed material ; in fact, the longer the dyeing operation the greater the loss of felting power, mordant dyeings being therefore more prejudicial. Chrome blacks are more difficult than other blacks, and likewise alum-mordant colours. Example (Reiser) :— white yarn which will give 18,000—20,000 metres per kilo, after

dyeing will only give 12,000—14,000 metres, especially after brown or black.”

Piece-dyed goods mill more easily than yarn-dyed fabrics, possibly because a little preparatory felting takes place in the dye-vat. If for after-dyeing, the milling should be stopped a little short of the full intention for the same reason, and a small allowance should be made for the washing-off process. Well-made pieces are best milled in the white, as milling is easier than after the dyeing boil. A mild Moser raising is sometimes useful before milling. Pieces run too dry in the machine cease to felt, and begin to “ merl’”’ or chafe, i.e., to lose flocks by excessive friction. If too wet, the felting action ceases again, probably for the following reasons :— 1. The buoyancy of the fibres when suspended in the liquid prevents their interlacing under pressure. 2. The fluid friction replacing the solid friction of fibre-to- fibre leads to easy disentanglement after removal of pressure. The fabric should be well moistened to the touch, but not wringing wet.

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MILLING SOAPS.

The question of soap in milling—the type of soap, the proper strength of solution, and the quantity employed—is a matter on which practical opinion has differed. It is, for example, a common statement that “‘ Heavy milling requires stiff soap.”’ It is not clear whether this means :— 1. That the soap should be a hard curd rather than a soft soap, i.e., a Sodium Stearate-Palmitate, as against a Potash or Soda Oleate soap ; or, I 2. That the solution employed should be concentrated, nearly a jelly. The first issue is discussed in the section on soaps and practical scouring ; but it may here be noted that the olein soaps tend to lose their lathering powers at higher temperatures, and the harder fatty acids—stearic, palmitic, etc.,—do not fully develop these powers at low temperatures. In any case, there is no causal connection between the molecular weight of the fatty acids of the soap and the weight per yard of the goods or the degree of felting. Practical experience in a heavy woollen mill and a light dress goods finishing trade has shown that olein soaps will mill as successfully as the white curds or other hard soaps ; and the olein type undoubtedly washes out more freely at low temperatures. In reference to the soap consistency, no exact data have been obtained ; solutions of 5% and even 10% are employed. It has not yet been determined whether felting is a maximum at a given concentration of soap. MHarrison’s experiments on Sulphuric and Acetic acids and on Caustic soda point to an optimum concentration, but little work has been directed to this item. The question is related on the one hand to the turgescence factor, and on the other to the best humidity for felting. 7 Some experiments made at the Leeds University, given by Mr. Walter Law, may here be cited :—

‘“‘ Several experiments were made, one of which we quote. The time taken up in milling the cloth was 40 minutes ; class of fabric, milled worsted. The weight of the cloth was 9 Ibs. 114 ozs. The strength of the solution—1 lb. white bar soap per gallon. The amount of soap solution made was 16 lbs. 43 ozs., and it was found that after milling the solution left weighed 12 lbs. 74 ozs. It + therefore took 16 lbs. 44 ozs. — 12 Ibs. 74 ozs., or 61 ozs. of solution to mill the fabric. As one-eleventh of the whole of the solution was soap, the quantity of soap consumed per 100 lbs. of material milled = 34 Ibs. of soap. Regarding the consistency of the soap from a milling standpoint, it was found that for dry milling the consistency quoted was all right, but when the cloth was wet milled, owing to the extra water in the piece, the amount of soap should be increased. The experimental point for wet milling was determined by using the same weight of cloth and a stiffer consistency of soap, viz., 1.3 lbs. of soap per gallon. This milling solution was tried with milled worsteds, milled tweeds,

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milled beavers and meltons, milled cheviots, of an all-wool type, and answered admirably for the lot. It may be interesting to note how the 1.3 for wet milling was obtained. The dry cloth weighed 9 Ibs. ll} ozs. On this being wet out and hydro- it was found to weigh 13 Ibs. 1 oz., and therefore contained. 35% water.

If, then, we increase the 10 lbs. of water 35%, we obtain AEA? =. 13.6 Ibs. of water per 1 lb. of soap, this solution is found too weak, but if the soap is increased in the same rate we obtain a = 1.3 lbs. per gallon for wet milling.” In stock-milling it is more difficult to mill to specified lengths and widths than in the Rotary machine where the functions are separated. If pieces are piled in the length in the stocks, the milling is greater in length; and if in the width, the opposite is true. There is still the impression that the milling of worsteds, and similar fabrics, is best done in the stocks as less liable to rigging. It is possible to obtain the slight milling, ‘‘ crushing,’’ required on some goods in the scouring machine by extra soap and hotter water. Interesting comparisons may be made between milling and water-shrinking, and milling and raising as regards dimensions, texture, handle, cover, etc.

FLOCKING.

The practice of adding flocks to a cloth during milling is intended to fill up crevices, producing a solid, smooth fabric ; they should only be added after the goods have commenced to felt, and in small quantities at a time, and evenly. The following calculations may be useful :—

1. Suppose the loom weight of a cloth to be 30 ozs., and the finished weight required to be 253 ozs. It is known from experience that the losses in scouring, raising, shearing, etc., amount to 30% and the shrinkage in length is 3%. How much weight of flocks is required ¢ Now the actual stock on the reduced length would be :— 30 times 100/97 = 30.92 ozs. per yd. ; the losses being 30%, the real weight will be :— 30.92 times 70/100, or 21.64 ozs. per yd. ; and this requires 25.5 — 21.64, or 3.86 ozs., of flocks adding per yard to bring up the weight. The actual weight of flock to be used will depend on the kind of material. The above gives a rough guide only. 2. Given a loom weight of 16 ozs., and losses in finishing of 29%, with a shrinkage in length of 5%; find the weight per yard of the finished fabric. The weight per yard on the reduced length is :— 16 times 100/95 = 16/73 ozs. per yd. ; with 20% loss :— 16.73 times 80/100 = 13.38 ozs. per yd. on final cloth.

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But cases happen where an extra inch or so per yard may sometimes be allowed in the shrinkage to balance the stretching produced in finishing. The addition of flocks to a cloth is best done on the back, both for greater evenness and because the subsequent finishing processes would tend to remove the material from the face ; face flocking might also cause differences of shade. They may be added by actual sprinkling by hand or by a slot and hopper device with a roller feed; both dry and wet flocking are practised. In the dry method it is much easier to distribute the flocks. The application commences as soon as the machine is started up, and when well distributed the soap is applied. Wet flocking is carried out in stages ; one-quarter, say, of the amount intended is taken when warming up commences and sprinkled upon the goods ; after a while the second quarter, and so on, thus ensuring the best conditions for thorough felting in. When excessive amounts of flocks are to be added, a half-dry and half-wet system is adopted, as a wholly wet flocking would allow the goods to be milled up before the intended weight could be added.

MILL RIGS, CRIMPS, CREASES.

The running of the pieces in length, which is the characteristic of roller as against stock milling, has the grave defect that creases, crimps, cockles, or mill-rigs are easily produced. The prime cause is the tendency of the piece to run in folds of a permanent kind, a defect occurring also in the rope or dolly scourer. A slight excess of pressure, an undue shock owing to the fall of the upper roller, may start a local felting on such a fold, which rapidly develops into a long crease. It is plain from the mode of formation that crimps once formed are permanent ; no remedies are applicable. The careful scourer will prevent their formation by proper adjustments of the machine, avoiding pressure, over-heating, drying-out, too rapid milling, etc. But the main reliance of the machine-man is in the frequent taking out of the pieces, and opening the folds by hand, “ shaking-out,’ as it is termed; stretching the creased portions, and generally varying the lines of running of the fabric. This is hand-work and means taking pains, but it is the certain way of avoiding the rigging of difficult cloths.

Another system, less usual, is to give a preliminary slight milling in the stocks before running in the roller milling machine. Or, take out the goods, especially in the case of heavy cloths, and reverse them end for end ; but see later.

Creased or cockled goods may have their origin at a much earlier stage than the milling machine ; any factor tending to

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uneven felting is a cause, e.g., uneven mixing of different qualities in the stock; variation in the size and twist of the yarn ; light and heavy places in the weaving, etc. In general, such faults result in a distinct transverse line or bar on the cloth ; finishing rigs are usually irregular. Pieces requiring long milling are prone to develop rigs owing to their lack of

Fic. 78. FULLING STOCKS.

(JAMES BAILEY, SLAITHWAITE, HUDDERSFIELD.)

pliability as felting-up proceeds; drying-out and resulting production of high temperatures cause creases in these goods. Uneven soaping is another finisher’s fault.

CHAFING OR RUBBING.

This is due to pieces catching or sticking, over-beating in the stocks, or heavy pressure from the rollers ; short blends ; excessive or too prolonged felting ; uneven or badly surfaced rollers or hammers ; and also the general cause of defects of milling, i.e., the running in wrinkles.

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ROLLING OR CURLED SELFEDGES. These may arise from the construction of the cloth, the selfedge being too tight ; it should always be slacker than the cloth. Sewing the lists is usually a sufficient safeguard.

2M

po go Gi

fy)

ij

Fic. SToOcCKs.

HOLES IN MILLING.

Tearing or piercing the fabric may arise from foreign hard bodies in the cloth or soap, from damaged rollers, throat, draft-boards, or spouts; or from these elements getting out

of position or with wrong spacing. The roller aperture should

vary from about 4— of an inch, according to the weight of

the goods. The edge of the spout should come close up to the roller. Flanges are the cause of much cutting. Over- ballooning of the pieces has been known to burst the fabric, especially with a sticky soap preventing the enclosed air releasing itself quickly ; otherwise, ballooning is an advantage,

as tending to avoid wrinkling.

Page 338

314 REMEDIES FOR MILLING FAULTS.

Several have already been mentioned in connection with the faults themselves, e.g., frequent removal and stretching out, sewing the lists, reversing the ends, machine adjustments of weights, and springs, etc.

Badly developed milling faults are usually incurable. The- cures are directed in general to bringing the wool into a plastic state while under tension, and cooling-off so as to retain the stretched effect, thus eliminating the creases ; in short, a species of mild crabbing for an extended time. Open-width scouring at a rather higher temperature may be tried. This is followed by producing as even a cover as possible on the raising machine. Re-milling by the stoeks the other way of the piece is some- times feasible. A shrinking process cannot follow on pieces of this type, as the faults tend to redevelop.

STAINS IN MILLING.

The milling process in itself is not one of the cleanest stages of cloth finishing ; in its lower grades, e.g., milling in the grease, it is one of the dirtiest. Milling machines usually absorb a good deal of power, say, 5-15 H.P., and require much lubrication ; this is a fruitful source of milling stains. The bearing stain is commonly a compound of machine oil of the mineral kind with wool flock, iron rust, and even brass corrosion from the bushes of the bearing. Solvents like petrol, benzine, etc., must be used to remove the grease ; oxalic acid for the iron, and intermediate washing with warm water. The brass flanges of milling machines often cause metallic stains due to copper ; they sometimes disappear with the careful application of a 2-5% cyanide solution. It is not a good practice to allow pieces to stay in the machine over-night. The average maker of milling machines, and indeed of finishing machinery generally, has not sufficiently considered the plant from the point of view of textile cleanliness. (See Chapter XIII.)

TANDEM OR DUPLEX MILLING.

The double milling machine having a second pair of squeeze rollers has undoubtedly points of superiority over the single type. It is possible to vary the run of the cloth in its approach to the second rollers and thus secure that alteration of travel and difference of direction of pressure which are primary elements in the felting; together with this, the elimination of incipient rigging. The speed of the tandem is usually slightly less, about 100 revs./mins., than that of the single machine, 120 and upwards, but the output is considerably greater. Some figures, given by Mr. Begg, are cited below.

Page 339

COMPARISON OF OUTPUT BETWEEN TANDEM AND SItInGcLE MACHINES.

CLASSIFICATION.

MILLING MACHINE,

TANDEM MILLING MACHINE.

Method of

Milling.

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single machines.

The output from a tandem machine is four times that of the

315

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316

between the pairs of rollers and keeping out the length, or conversely of applying compression warp-ways. Thus fabrics with a worsted warp and woollen weft may be milled so as to produce the shrinkage in the width only. The possibility of

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inserting lateral rollers, mouthpieces, or special spouts between the two roller-sets is another advantage of the tandem miller.

The Theoretical Mechanics of Milling Machinery.

It may be taken from the preceding discussions that by far the greater part of the felting of a fabric is due to fibre interlacing. Even if serration-interlocking plays a material part, it will be facilitated by increasing the area of contact of the different fibres. The best means of bringing about rapid and thorough inter-meshing by mechanical action has received neither theoretical treatment nor experimental research, only the routine of the milling shed and the empirics of the machine maker have as yet been applied to fulling mechanisms. On mechanical principles, milling machines may be divided into three principal types :—

1. Gravity stocks; raised by cams or tappets and falling by their own weight. 2. Stocks with mechanical thrust; by eccentrics, cranks, etc. ; with numerous variations, such as the pendulum stocks, having mallets actuated by connecting-rods from a cranked shaft; horizontal stocks, etc. 3. Roller millers; including the ordinary rope milling machine, tandem millers, compound washing and milling machines ; and a number of forms embodying pressure or impulse mallets along with the rollers.

It is obvious that these several classes differ in their dynamical principles and it is well understood by practical fullers that the finishes produced on the fabric exhibit slight variations. The most fundamental difference lies between the roller machine and the others, and consists in the fact that in this type the cloth itself is in motion in addition to experiencing external forces. In the stocks, the fabric is practically quiescent during the intervals of application of the impulsive forces or pressures. Plainly, much is gained by this motion of the cloth as a mass during the circulating in the machine ; due to this cause alone, there must be a great deal of mechanical action favourable to intermingling of fibres. In order to achieve the maximum number of entanglements of fibres within the fabric, the mechanical necessities are :—

1. Application of force to secure relative fibre-displacements in the interior of the fabric and yarns. 2. Frequent changes in magnitude and direction of these

applied forces; mere dead pressure will not cause felting.

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318

A second fundamental difference in the roller type, as distinct from the stocks, is that in the former the cloth is

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merely subjected to pressures, while in the latter the effects are those of impulse, blows, or shock. The distinction is of extreme importance. The effect of a blow upon a body, say

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319

a hammer upon a heated metal blank, is not entirely a matter of the weight of the hammer, but depends also upon the velocity of striking ; it is in short proportional to the kinetic energy. Upon the hot blank the effects produced are conditioned by the elastic properties of the material ; a permanent change of shape is produced when there is little elasticity and the body struck is incapable of motion. For example, a mass of clay—a substance devoid of elasticity —is permanently deformed by a blow. If, on the contrary, a blow falls upon the highly elastic face of an anvil, part of the energy is returned to the hammer and causes rebound. In intermediate cases, the bodies continue jointly in motion, e.g., a hammer striking a nail in wood ; here both nail and hammer move forwards until the internal resistances of the wood disperse the applied energy as heat of friction. This must be largely the state of affairs in stock-milling, where a series of blows is dealt upon a softened plastic mass of woven yarns. Some of the energy is expended in producing vibrations ; in metal forging, probably a third disappears in this way in the final form of heat. Now the requirements of fibre entanglement do not necessarily involve a mass-displacement of the fabric ; mere changes of shape of the mass, or tumbling over of the pieces bodily, so far as they do not interlace the fibres in the yarns, are primarily useless; the secondary effect of producing uniformity of felting is not here regarded. It would therefore appear that the use of impulsive shock for cloth felting, as in stock-milling, is a mechanical error. The faller type of stocks may be treated from the mechanical point of view, as a body dropping freely under the action of gravity. Assume as an average case a three-tappet wheel running at 20 revolutions per minute. This gives for the mallet heads a rise and fall of one per second, and if we further assume equality in time for these, we have, from the laws of falling bodies, V = G x T, or V = 16 feet per second ; that is, the hammer meets the cloth with a velocity of 16 feet per second, probably in practice rather less, perhaps about 10-12 f.s._ The piece is now violently compressed, the fibres suffer much displacement relatively to each other, new intermeshings are formed which do not wholly disentangle when the hammer-head begins to rise; in short, felting takes place. The time of contact of the face of the mallet with the fabric is hardly calculable, as we are completely ignorant of the elastic properties of fibres spun into yarns and woven into a texture in this respect. In the blows of a smith’s hammer on an anvil, it is of the order of the of a second, but in the present textile case it is certainly much longer, the material being elastically imperfect. It is perhaps of the order of a few tenths of asecond. An over-rapid action of the stocks

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is not practical, as this time of contact is unduly shortened. Moreover, the more instantaneous the impulses tend to become, and the more the material is structurally destroyed. If heavy and rapid blows were all that the case demanded, a steam hammer would be the mechanical ideal ; the practical result, however, would be unlimited fibre breakage. As a rule, a blow

Fia, 82,—EccrentTrIc STOCKS.

requires more energy to produce a given change of shape than a steady pressure; the effect of a pressure is transmitted to the interior of a body—an end eminently desirable in felting — the time of action and the elastic reactions of the material entering into the problem.

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Consider now the second class of milling appliances, viz., hammer actions driven by mechanical thrusts. Whether these are actuated by connecting-rods from cranked shafts, eccentrics, etc., the type of motion resulting is the familiar conversion of circular into reciprocating :—Simple Harmonic Motion. Taking a horizontal stock-miller as an example, the throw of the mallets being I foot and the speed of the driving shaft 150 revs /min., we have for the total period T = 60/150 = 0.4 secs., and the amplitude A = I foot. The laws of the motion are given by the equations :— S =A X-sin BtorS = A x sin (360/T) t V =.AB xX cos Bt or V = AB xX cos (360/T) t where “8” is the displacement at any instant “‘ t ’’ seconds from the start taken at the middle of the path; ‘‘ A.”’ is the amplitude or throw; “B”’ is really the angular velocity— here taken in degrees per second—of the crank In the case mentioned above of speed 150 revs /min., and throw 1 foot, the velocity is, of course, a maximum half-way along the throw, and is :— Vise bt Cen: 900-4, and this for t = O gives V = 15.7 feet per second. Thus this type of stocks has a maximum velocity of striking the fabric quite comparable with that of the fallers. It will, however, depend upon the mode of packing the box whether any blow is struck at all; in a full box, with cloth in contact with the face of the mallet, the mechanical action is that of pressure throughout. This pressure is a maximum at the middle point of the throw, and diminishes according to a simple harmonic law to zero at the end of the throw. During the retreat of the hammer, the elasticity of the fabric may cause it to regain somewhat of its dimensions, but it is in the forward stroke that the felting occurs, much as in the faller stocks. It is interesting to compare the various types of milling machines from the standpoint of what an engineer would call their Latency or idle period. It is plain, for example, that in the case of the faller stocks of one second period, half of this, at least, is occupied by the lift. If the time of fall is calculated from the distance, say, 2 feet, we have t = 1 (28/2) = (2/32) = {second ; perhaps another } second or less is actually expended on compressing the piece, and in general, probably three-fourths of the time is useless, as far as action on the fabric is concerned. In the horizontal stocks, period 0.4 second, half of which is retreat, then if the cloth in the forward stroke is always in contact with the face of the mallet some - action must be going on; but at the ends of the throw, when the velocity is small, this can only be slight, and in this case also well over half the time of action is lost. Now in the roller machine the fibres are probably undergoing some relative

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displacements during the whole run, either by the pressures of the parts of the machine or by their own bendings as the path of the fabric is changed. Obviously there is here great superiority, and it extends to other mechanical aspects. The impulsive shocks or blows of the stocks are here replaced by pressures. It would not be possible to produce feltings in a textile fabric by replacing the impulses of the stocks by equivalent dead pressures; there must be variation of the lines of action, and also with advantage, of the magnitude of the pressures. But the short periods of stress characteristic of the stock type are eliminated in the rotary miller, being substituted by the squeezing actions of the throat, rollers, spout, etc. Probably a “ kneading ”’ type of action would be superior if it could be easily mechanically attained. The great defect of the roller milling machine is the excessive friction on the fabric by the parts of the machine, leading to abrasion and production of flocks and general weakening of the yarns in the warp and weft. (Cf. p. 256.) This friction produces heat, and conduces to the turgescent state; but frictional heat is expensive and could be easily obtained by cheaper means, say, by a steam pipe in the machine. The linear speed of a fabric through a roller machine may be about 6-8 feet per second, the revs./min. varying from 80/120. ~ Thus, in spite of its improved mechanical principle, the roller miller causes more flocking, or waste of fibre, than the stocks ; its average working temperature is, of course, much higher.

GREASE MILLING.

A German writer, M. Redjan, sums up this process, dis- agreeing with the general practice of milling in the grease. Military cloths which require a long milling to give a close thick result, for example, a cloth whose diminution in area is as 2 to 1, must be milled in soap. The dirt in the cloth is a serious factor. The release of the tension and movement of the fibres is hindered and longer time is required, which negatives any other advantages. Cloths having much tension in the raw state have to be scoured before burling and mending. Fresher colours are obtained by scouring first. Although grease milling gives a more compact cloth, this is not always an advantage ; it is, for example, necessary for riding breeches but not for mantle cloths. With heavily sized warp and inferior weft, the grease forms with the glue a sticky mass which prevents air from escaping, with the result that balloon- ing takes place and bursts occur forming numerous holes. Short grease milling of 5-10 minutes will often shorten the time of scouring. The saving of 4 lbs. of soap per 100 Ibs. cloth is small compared with other economies such as may be obtained.

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A useful device for wetting-out pieces with soap or alkali, in default of a “lecker,” is a shallow trough with rollers or rails, one of which must be at the bottom ; the cloth is dragged through this by the aid of the ordinary wringer, the bottom rail securing its thorough immersion.

Finishing Routines (Wet Processes).

In the description of special operations, there has been of necessity much information given on particular fabrics, but it will be useful to collect some further items into a joint discussion. Wool fabrics may be divided for this purpose into the three classes of :—I. Fine Worsteds. II. High Class Woollens. III. Low Woollens.

I. THE WORSTED FABRICS, in general, go through the finishing processes without radical disturbance of the yarn structure or the weave, the usual standard being the ‘clear finish.’ In cloths with much complexity of design, often accompanied by great variety of colour, the entire routine is directed to securing a clean, bright fabric with the minimum of textural alteration. After the usual preliminary work—mending is an important and difficult stage in worsteds, where no milling or raising follows to cover up the operation—worsted pieces may receive light scouring on the lines of p. 199. It has been mentioned in the section on crabbing that crossbreds, gabardines, etc., will need prior setting. In the lower qualities, serges, etc., go straight for dyeing in the piece ; this is possible because of the low oiling on these goods. This crabbing and dyeing to follow is the routine known in the trade as the “‘ Leeds Finish’; it is successful because of the general cleanliness of the worsted spinning process. The finer qualities of Botany indigo plain serges, etc., receive a proper scouring before piece dyeing. Some very light cloths are run in the open-width scouring machine. Certain worsteds are given the semi or half-milled finish, which consists in a short run, ten to twenty minutes, in the roller milling machine; this is really a crushing rather than a felting process, and in many cases the stocks are preferred for this purpose. A crossbred piece will give the clearest finish, but would be deficient in handle, the slight milling compensates for lack of quality. Excellent handle primarily goes with fine wool quality; finishing operations can only contribute to a partial extent. Ordinary scouring is sufficient to develop the properties of good wools, but the slight milling or crushing is required in other cases. Some finishers give the moderate milling necessary in the grease ; in other instances an extra run in the dolly with abundant lather is given. Superfluous fibre is well brushed up and cut

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away. Estamines, worsted flannels and suitings have the semi-milled finish. In generai, the worsted cloths do not lose more than 5% of the grey weight during the finishing process. Steaming and brushing are essential stages in the production of clear finish and soft handle, and blowing is important to

Fic. 83.—CRABBING & WINDING-ON MACHINE.

(Lodge & Oldroyd’s Patent.) (Witt1aAM WHITELEY & Sons Lrp., Lockwoop, HUDDERSFIELD, )

secure regularity in the run of the weave or design. In cloths. with a pronounced twill or rib, the flattening effect of some operations must be avoided ; for example, corkscrews, gab- ardines, etc., require careful treatment in the plastic stages, such as blowing and pressing, and particularly crabbing. Clean cutting, aided by brushing or the sand-emery roller is an important item in clear finished worsteds.

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The “ vicuna”’ finish is a mixture of worsted and woollen methods adapted to the special nature of the fabric. In some cases the cloth is crabbed or double blown, but other finishers would omit this. The scouring is on worsted lines and the milling moderate. The fabric is raised damp and further slightly milled, preferably in the stocks, and washed down. After tentering it is piece-dyed. Fine quality vicunas are boiled ; some finishers give instead some rounds of steaming and batch upon rollers for several hours, frequently reversing, to prevent draining and capillary creep. A _ repetition of washing off, tentering and wet raising with slight milling follows. The ordinary finishing routine of cutting, shrinking, etc., may then be completed. The characteristic feature of this finish is the joint use of raising and milling to produce and fix the fibrous surface in its typical form. All finishes are varied according to circumstances and standard of excellence, and the above would be modified in shops where rapid output is essential. The best vicunas are hydraulic pressed in papers, slowly and moderately, the handle needing to be full and firm, but not stiff. Blowing must not be excessive for this reason, ‘and some cloths merely get a cold flatting in the press stage, as the surface must not be too lustrous. The older finish of vicunas was performed in the raising stage on the teazle gig, both sides being raised with reversals, as the cloth is not required to have a “‘draw.’’ A proper wetness is maintained as the fibre must not be pulled from the cloth.

Il. THE WOOLLEN ROUTINE.

In cloths made from woollen yarns there is much greater variety of finishing than in worsted fabrics. The characteristic operation on the woollen texture is milling, but outside this there are several typical finishes. In the ordinary “‘ tweed ” finish of a Saxony suiting or costume cloth, the fabric is intended to have a soft face with cover developed in the milling. In the lower qualities, these would be scoured and felted in one process in a special combined machine, or even milled in the grease. Fine qualities should be treated by the Saponi- fication Scour (see p. 223), then milled, say, half-an-hour with soap and washed off in the dolly. The cover is the product of the milling and the cloths in the medium weights would not be raised. Little or no press lustre is given, in fact the cloths often get a blown finish only. The loss in weight might be about 12—15°% on good qualities. Heavier cloths of this class receive some raising upon the milling cover. The “ Khaki ”’ military cloths for uniforms and greatcoats were finished in various ways :—by soap, grease, or acid milling, according to the individual practice of the different mills.

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The face-finished woollen fabrics, meltons, boxcloths, beavers, pilots, doeskins, etc., have a distinctive routine directed to producing a dense cloth with a fibrous surface forming a “ pile,’’ and considerable lustre. As an example, the melton finished woollen is set widely in the loom to allow of great shrinkage weftways and a densely milled cloth; the milling is the critical operation on which subsequent processes depend. 30 or 40% contraction in a milling run of from three hours upwards in the roller machine, is necessary in these goods. The scouring may follow the usual woollen type, i.e., the saponification scour, and the milling must be carefully regulated. Sufficient soap to show the slight froth when a handful of the cloth is squeezed, is kept in the fabric, and no over-heating is permitted. The cloth must be reversed at least once during the run. After washing off and centrifuging, the pieces may be dried over rods or tentered without pulling. Brushing, cutting, blowing, pressing and steaming follows. In beavers and doeskins the pile is laid in one direction, but not in meltons. A beaver routine, for example, after milling, might include raising 4—5 sides for 15-20 minutes each, tentering, dry beating, cutting, pressing ; then boiling three times for 3-4 hours each at 160-170°F.; piece-dyeing follows, and_ straightening, tentering, cutting, blowing, pressing and steaming off. In double cloths, the finishing results are greatly in the hands of the designer, and the choice of materials, weaves, setting, etc., controls the behaviour of the fabric almost exclusively. In order to get regular shrinkage, the miller must adopt all the precautions :—bagging or tacking, opening out, reversing, straightening of lists, etc. It is essential that the material should have good milling quality, attempts to stint quantity or employ inferior fibre invariably lead to trouble in crimping, etc. Heavy goods often give the miller much anxiety in the curling of selfedges ; the prunella weave, much used to give thick bulky handle, is notorious in this respect.

lil. LOW WOOLLEN ROUTINES.

The finishing methods of this class of goods are those of the corresponding straight-wool cloths, the special difficulties arising from the nature of the raw materials. The term ‘* Shoddy ”’ is used by some to indicate all material resulting from the disintegration of rags; mungo comes from fabrics that have been milled. ‘“‘ Extract ”’ is the product of material that has been carbonised. Cotton is used in all forms, in the blends and as warp and weft. It is plain that the use of recovered wool opens the door to all kinds of chemically treated fibre, e.g., carbonised, sulphur bleached, chlorinated for shrinking, water-proofed, etc. Hence the scouring and milling

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of these union goods offer special dangers over and above those of the poor quality oilings. Some hints on these particular goods are given in the section on practical scouring. The low worsteds made largely of cotton receive as little finishing as possible, owing to their readiness to develop friction streaks and rub-marks. In the woollen fabrics the milling difficulties are enhanced owing to the absence of felting property in the cotton elements and the reduced felting power of the recovered wools. It sometimes happens that after a certain stage of milling such fabrics begin to pull out instead of shrink. The tandem or double fulling machine is largely used on such goods, and combined milling and scouring plant also.. Staining methods are employed on these cloths. There are great wastages on such goods, due to large per- centages of oil and also to profuse flocking away in the milling ; in low cheviots, having both warp and weft of shoddy and low woollens wholly of mungo, as much as 30% may be lost. The difficulties of low woollens concentrate largely round the presence of mixed fibre. Cotton enters as yarn of pure fibre and admixed with straight wool, mungo or shoddy. It may form the warp, as in both woollen and worsted cloths, over- coatings, velours, or lustre cloths, and with mohair; as weft it enters into gabardines with a worsted warp. Blended with wool it forms the so-called Angola yarns, and is blended to give strength to recovered wools. The milling process is severely affected by the presence of cotton. All degrees of shrinkage are required in this section of the trade; ordinary union flannels (cotton and noils) may run up in width one- eighth to one-sixth, while low grade meltons and beavers need weft contraction of one-quarter and one-third. In extreme cases, e.g., submarine cloths, 50-100% shrinkage is secured. The practice of flocking is another of the special features of the low trade. The important point to the miller is that the flocks should have good felting qualities ; they should prefer- _ably be cut flocks, the grinding processes tending to destroy the fulling quality. The cloths must invariably be bagged or tacked, i.e., sewn down the lists face inside, so as to cause all flocking to take place on the back of the cloth. Flocking causes much variation in the milling routine, tending to encourage width at the expense of length, and absorbing the soap ; the attention and judgment of the miller are more than ever necessary. Bagging is very necessary on low goods for the protection of the face of the cloth. For the same purpose, multiple drafting is desirable to secure the action of cloth upon cloth, rather than that of the wood of the machine on the cloth. But a proper cover felting, shrinkages in width and length are all inter-related, and their separate development must be osberved and the arrangements modified accordingly.

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Es va A 2 x)

Fia. 84.—FOLDING, RIGGING, ROLLING ann MEASURING MACHINE. (Wm. WuiteLey & Sons, Lrp., Lockwoop, HUDDERSFIELD.)

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Multiple drafting teads to rapid shrinkage in width; if the cloths come up too slowly in length, they must be run singly and weighted in the spout. Low grade goods may require straightening out during the milling, to prevent crimping at the lists, and at the close of the milling they should be fully opened and cuttled straight; they must not lie in warm irregular heaps. I

The difficulty of low worsteds in respect of friction markings is accompanied by the colour bleeding, owing to cheap dye- stuffs of poor fastness ; the goods should be worked as little as possible. There are, however, some problems which the scouring department should not be asked to solve. The inherent hardness of the cotton is an obstacle to all attempts to secure softness and handle. Plaid-backs made in low grades are particularly apt to show on the face if the back lacks felting quality, especially if the wool is too long and coarse ; the remedy lies with the designer and the use of finer and shorter wools of good milling property. Such cloths must not be over-milled and the length must be kept out, the shrinkage being confined largely to the width. Unions of light shade are sometimes scoured in special machines con- sisting of a number of troughs, 4—5 or more, each fitted with squeezing rollers, the cloth being slowly passed through the liquors and from one to the other.

The leading facts of a milling trial may be obtained from the results cited below on a coarse serge made from yarns of East Indian wool and worsted pullings and woven with an ordinary 2/2 twill for a cheap cloaking. It was soap-milled in the roller miller running two drafts. At intervals the cloth was taken out, measured and a pattern cut off.

TIME. WIDTH. SHRINKAGE. SHRINKAGE / TIME. 58.0 sai 15 56.7 1.3 0.087 30 56.0 2.0 0.067 45 55.3 2.7 0.060 65 53.5 4.5 0.069 85 52.0 6.0 0.071 105 51.0 7.0 0.067 120 50.0 8.0 0.067

Up to this point the shrinkage has been almost perfectly linear, i.e., directly proportional to the duration of the milling ; the equation connecting these factors is Shrinkage = 0.067 x Time. If the piece had been further milled, this would have been modified. On the portions removed, strength tests were made both warp way and weft way, taking the usual standard sample on the Goodbrand machine.

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186.5 13 183.5 18 194.0 12 194.0 13 188.0 13 181.5 118 193.0 13 175.0 12 195.5 14° 184.0 21 211.0 13 186.0 2 223.5 175.0 255,

The effect of the milling in breaking up the yarns, causing a greater extensibility and general weakening is clear ; also the increase of the strength warp way, owing to the condensation of the ends into smaller space.

hed tid fe LAI

Fie. 85.—MILLING MACHINE.

(JAMES BaiLey, SLAITHWAITE, HUDDERSFIELD.)

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The appended table gives a comparison of the Scouring and Milling Costs (apart from labour) on three woollen pieces of

medium quality, each weighing 100 lbs. :

I. Scour with Alkali and mill with Sows; i.e, a saponifica-

tion scour with alkali, 80 gallons at 8 Tw. Water, for alkali and washing off, 480 eons Soda Ash, 40 lbs., at £6 per ton Milling soap, 8 Ibs., at 5d. per lb. Washing off after milling, soap, l lb., and water

I Total II. Scour with Alkali and mill with Acid. Scouring, as above .. Milling ; water, 300 gallons” D.O. Vitriol ; 6 Ibs. at 3d. per lb. Washing off after milling ; water Total III. Milling in the Grease. ‘“ Lecking ” prior to milling ; water ie Soda Ash .. Soap Washing off after milling ; water Soda Ash Soap .. Total

Fic. 86.—LECKER OR SOAPING MACHINE. (JAMES BAILEY, SLAITHWAITE, HUDDERSFIELD.)

d. 6

30 40 11

87 36

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It is seen that when circumstances permit it is much cheaper to mill with acid, as in the second method, but the quality of the materials, etc., must always be considered.

EFFECT OF WEAVE IN MILLING.

Contraction is necessarily dependent on the method of interlacing. Comparison in such standard weaves as the plain, prunelle, 2/2 twill, 3/1 twill, broken swansdown, shows that the degree of shrinkage is governed by (a) number of interlacings ; (b) the order. With the exception of the

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Fie 87.—COMBINED MILLING anp SCOURING MACHINE.

(JAMES SLAITHWAITE, HUDDERSFIELD.

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prunelle, the intersections are regular in each thread and pick of the weaves named. Assuming the setting of the warp to be the same for the five weaves, the unit of measurement would vary with the number of threads between the intersections. Taking 30 threads per inch in the loom, the unit would be :— Plain weave, 35; 2/2 twill, 7; ; 3/1 twill, two, #7, and 34 inch in succession. The fixed law in fabric structure will therefore be :—‘‘ The greater the unit, the freer the fabric shrinkage.”’ Experimental weaves in Saxony and Cheviot yarns gave :—

SAXONY. CHEVIOT, Plain 29.00% 22.25% shrinkage. Prunelle 34.75 30.50 2/2 twill oo. 10 3/1 twill 34.75 27.25 Swansdown 34.75 30.50

The change in the grouping of the intersections causes a change in the amount of shrinkage. The plain weave makes for firm and close cloths with maximum strength. In coarser weaves, such as the higher twills 3/3 and 4/4, the long “ floats ’’ produce opener and looser cloths. If the intersections are frequent, it is plain that the milling and felting of the cloth will be resisted and the handle will be harder ; obviously also, in the plain cloths it is desirable that the shrinkage should come from the length and width in proportion. As, however, the process of manu- facture generally requires stronger warp than weft threads, it results in finishing that certain operations are almost confined to one set of yarns, e.g., raising is mostly borne by the weft and milling is greater proportionally in the width.

Page 359

MINoR PROCESSES.

Page 361

CHAPTER IX.

Minor Processes.

The Blowing Process.

This consists in subjecting the wool fibre in piece form to the action of steam forced through under its own pressure. The term “ decating”’ or “‘ decatising,’’ of French origin, is used for blowing, but it is also used for crabbing and even for mere steaming; in these loose applications it is best avoided. Some reference has already been made to the blowing process in the section on crabbing, but it is employed as a distinct finishing operation and requires special notice. The essential feature of the process is the application of steam under conditions amounting to partial enclosure to the cloth while in a state of strain, the subsequent cooling off producing permanent setting on the fibre. The sub-variations comprise :— 1. Blowing the cloth in the wet state; this has been described already in the section on crabbing as a part of the general fixation of cloth structure. 2. Blowing in the “grey ’”’ or “‘ greasy ”’ state, i.e., from the loom. This is a quicker and less troublesome process than crabbing, for which it is often substituted. 3. Blowing dry as a part of the finishing routine. 4. Blowing under pressure, preceded sometimes by a vacuum stage. In the finishing routine, blowing generally follows cutting, perhaps after a cutting and steaming round. It is important to correct common fallacies respecting the objects of blowing, viz., that it is intended to impart lustre and condition to the fabric. Both these results occur—and are sometimes not desired and have to be removed—but it must be clearly under- stood that the primary aim of the blowing operation is to set the fabric in a regular and permanent manner. To this end, the cloth is wound upon the perforated blowing roller with

=

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some tension into a roll, the general arrangements being those described under the crabbing process. Under the influence of the hot steam—at the boiling point 212°F. or 100°C.—the wool becomes plastic. The winding-on tension is relieved, all extraneous or accidental strains shown in creases, crimps or other markings, are similarly relaxed, the fibres of the yarns and the yarns themselves assume an equilibrium controlled only by the geometrical relations of the weave, the final result being a regular, balanced, unstressed texture. This is now fixed by the cooling off, usually by a current of cold air pumped

BZ ws]

Fia. 88.

reg == a ae

Fig. 89.

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through the roll. It is evident that blowing gives marked and valuable characters to the woven cloth not produced by any of the other finishing routines, and the bulk of fabrics benefit by the process. There is some scope for inventors in applying the blowing principle in the finishing of hosiery, where the difficulties are great, but the results very desirable. Blowing is, however, neglected by many cloth finishers, as there are pronounced secondary effects not always intended; it is further quite easy, by careless working, to produce serious damages.

rig

or SS ot

I

\

I

Fie. 90.

Among such secondary effects are :— 1, LUSTRE.

This is a consequence of the improved regularity which is seen in the parallelism of the yarns and the straightness of the twills, checks, or other weave elements. There is probably also a slight flattening effect due to the pressure produced in the layers of the rolls. The general result is to substitute a regular instead of a diffused reflection of light from the surface of the texture. If the lustring finish due to blowing is excessive it is removed by open steaming.

Y2

Page 364

Fie. 91.

Fig. 92.

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341 2. CONDITION OR REGAIN.

That is, sorption of moisture. The question of the increase or decrease of content of moisture in a blown piece is of some interest in the light of the preceding discussion on humidity and wool. It must be noted that whatever the boiler pres- sure of steam on the blowing roller, the actual pressure in the cloth is atmospheric. The author has placed ther- mometers in the roll on blowing machines supplied at high and low pressures with the identical result in both cases of 100°C. or 212°F. Plainly, the cloth offers practically no resistance to the passage of the steam ; there is a rapid expansion to the pressure of the free atmosphere and the usual fall to the corresponding temperature follows. Now consider the action of the steam during the blowing. In the early stages, there is a condensation upon the cold wool which would be perfectly calculable from a knowledge of its temperature and specific heat, allowing for the water of condition. This condensation continues until the entire mass of the roll reaches the tem- perature 100°C., and during this stage some sorption by the wool may occur. Perhaps the wool acquires some water of imbibition, but this must be slight in the time available ; in the lack of experiment and observation this is indeterminate. When the roll is at boiling point, free steam blows off from the surface, and this is permitted for 1-2 minutes or more. In this portion of the operation it is extremely unlikely that there can be any gain of moisture by the wool tissue; it is more probable that there is some loss. We have no experi- ments regarding the moisture content of wool in saturated atmospheres at the higher temperatures. On cooling by the cold air suction, some moisture can be deposited, especially if the steam, as is always the case, is wet steam, i.e., carries some suspended water. Not much water could be gained from the enclosed steam, as the total volume of both wool and steam in the roll is only a few cubic feet, and a cubic foot of steam at the ordinary pressure weighs only 0.0376 lbs. ; it follows, therefore, that such steam could only give very few ounces of water to the cloth. (Note.—If the steam is ‘‘ wet ”’ steam, the circumstances are altered.)

Now blown pieces on unwinding from the roll commonly feel very damp, and it is instructive to examine this phenomenon, as it occurs also in cloth pressing. Prof. Roberts Beaumont notes: “The moisture or humidity which arises at the com- mencement of cloth pressing, etc.” and it is a familiar matter to the operators of mechanical presses of the rotary or inter- mittent type. In the blowing case, part of this damping is certainly a mere dewing effect, as the enclosed steam is condensed by the cold air draught. But there is another

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factor. It has been noted and emphasised in the discussion of conditioning methods that wool takes up, from an environ- ment of constant relative humidity, less moisture at the higher temperatures. The regain curves of Hartshorne and Schloesing for the temperatures 12, 24, and 35°C. illustrate this clearly. Even at the comparatively low temperatures of 12°C. and 35°C. for a constant relative humidity of 51°% there is a fall in the regain from the value 14 to the value 13 parts per 100 weight of dry wool. Hence, from a given regain, say of 16%, as the wool is warmed up in the roll it approaches more and more the saturated state for the higher temperatures. (See table of Worsted Regains, Temperatures and Humidities, p. 374.) At 100°F. this would be already less than 14% and at higher temperatures very much less. (Compare section on heating of wool, in Chapter X.) Hence the wool “ sweats ” at the higher temperatures, a phenomenon very apparent— and sometimes very troublesome—in the rotary and other types of press; this moisture may deposit on near metallic parts and cause rapid rusting, with consequent staining. Part of the dampness of a freshly blown piece is due to this special moisture. The blown piece, even though damp, feels harsh, as the practical finisher well knows; it evidently lacks its normal regain proper to the lower temperature, but reconditions itself throughout the fibre on standing. In practice, it is recognised that blown pieces should not be sent to the press immediately unless a hard smooth “ cotton ”’ finish is required. Certain factories direct a current of cool air against the fabrics on delivery from both tentering and blowing machines.

3. PRESSURE EFFECT.

It has been shown in the description of the crabbing operation that the winding of the fabric under tension upon a roll produces an internal pressure between the layers. This pressure, as in crabbing, occasionally produces the so-called ““ water-marks.’’ True water-marks are sometimes encountered in blowing, as a result of bad draining of the blowing rollers, oi the condensation water from the steam. This liquid, forced through the roller wrappings into the cloth causes markings which are invariably accompanied by some staining. They can be prevented by blowing the roller free from condensation before closing the terminal valves and also by fitting the roller with self-draining nipples. Pressure marks are not accom- panied by staining. For the rest, the remarks under Crabbing apply to this case also. The mechanical pressure due to rolling under tension is sometimes employed in finishing as a substitute for the regular pressing operation, especially if the blowing is carried on by

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the help of a cotton wrapper. Quite a distinctive finish is obtained on many worsteds by this means, particularly if the piece is double blown, i.e., run on twice, reversing the head and tail ends. Attention must be given to the surface of the wrapper. Much of the Khaki made during the War received the blown finish only, and on woollens, which should not be flattened overmuch, it is a useful method.

Fig. 93.—ENCLOSED or PRESSURE BLOWING.

4. SHRINKING.

This invariably results from the blowing process, the piece- width usually contracting 1-2 inches, and if the piece is blown without wrapper and with much tension, three or more inches. Even when the blowing is conducted by a wrapper, some shrinkage occurs and the blowing of a cloth is often employed as a part of the routine of shrinking. A second blowing yields a further shrinkage, but of only half the first amount or less.

5. GHANGE OF SHADE.

Some dyestuffs are affected by hot steam, e.g., the sulpho- cyanines, etc., and white yarns suffer some browning action, which varies in degree with the amount of exposure.

6. HANDLE.

The blown piece feels thinner, firmer and more solid, and if the blowing is excessive, quite papery; there has been a levelling and flattening action on the surface of the cloth. A steaming off corrects this. The final effect in the coarser and harsher wools is very beneficial.

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344 PRESSURE BLOWING

In this variant of the blowing process the pieces are batched on a perforated roller which is contained in a cylindrical enclosure. As a first stage, this enclosure may be partially evacuated, which will at once remove most of the air and some of the moisture of the wool. Sometimes warmed air is blown through at first, with the idea of preventing the initial

Fie. 94.—BLOWING MACHINE: DovusBLE ROLLER AND TAKE-OFF MOTION,

(JAS. BAILEY, MAKERS, SLAITHWAITE. )

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condensation when steam follows. The steam is admitted and a pressure is allowed slightly in excess of atmospheric. Thus temperatures up to about 220-235°F. are permitted. The usual cooling off by cold air follows. The differences between this and ordinary blowing consist in the working on fibre at a lower initial regain and the use of a higher final temperature, thus leading to an intensified “ setting’ action. This process is the basis of the so-called ‘* permanent ’’ finishes.

CONSTRUCTION OF BLOWING MACHINES.

A convenient arrangement for rapid and efficient blowing is to put two double roller machines side-by-side on the same exhausting pump. In this case, each machine has a front and back roller fitted with steam entry cocks, exhaust valve to air pump, friction brake and twitch rollers. Each machine has a drip kettle, to secure dry steam. The rollers are perforated with holes about ?# inch apart, and ;,—;4, inch in diameter, the rows being 1 inch apart. The roller itself is best made of aluminium, an introduction made by the author and found to be very incorrodible, clean and non-staining. The perfora- tions should be nippled for the automatic draining of condensation. In this system the operatives may be winding on one machine while the other is being cooled off by the pump. Piston pumps and rotary pumps of the Roots’ blower type are used.

The Shrinking Process.

It is a matter of common observation that wool garments undergo a diminution in dimensions during the period of wear. The final results of wear are a disintegration of the fibre of the wool, partly by attrition, but garments frequently become unwearable by shrinkage long before the fibre is thinned away. The terms applied to fabrics in this connection are distinguished by a common lack of exactness. Among such are :—Shrunk, Soap-Shrunk, Guaranteed Shrunk, Double-Shrunk, London Shrunk, Unshrinkable, etc. Some of these connote distinctive processes, but there are none which can be quantitatively defined on the finished cloth. A broad definition of the last term might run as follows :— A fabric shall be deemed ‘*‘ UNSHRINKABLE ”’ when, during the life of the fibre, garments made from the cloth do not contract so as to become unwearable. Thus, suppose a garment measures, when newly made, one yard in a principal dimension ; if before the wool is so thin as to wear into holes, this does not contract more than one inch in the yard, it will continue to be wearable without sensible inconvenience or loss of appearance. The restriction

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would amount to about 3%. Many fabrics in which shrinkage is important can, by proper construction and technical treat- ment, be brought to this standard, and such materials can be fairly styled “‘ Unshrinkable.”” But there is no general trade agreement on these questions. The process of scouring produces some shrinkage of pieces, both in width and length, which is usually denoted by the term “‘ soap-shrunk.”’ The object of the shrinking operation is to forestall the diminution in dimensions—width and length—of the cloth. This is effected by bringing the wool into a semi-rigid state while freed from all external stresses, usually by a thorough wetting under conditions ; as a rule no heating is used in the shrinking stage. Shrinking differs from milling in the factor of felting or interlacing of fibre, which occurs only to a slight extent in shrinking. As secondary effects, shrinking adds weight to the fabric in the form of full or excess ‘‘ condition ”’ ; and confers a lofty, cool, and acceptable handle for much the same reason.

Methods of Shrinking may be classified as follows :—

1. Hand Shrinking process. 3. Blowing. 2. Machine processes. 4. Chemical processes.

Hand Shrinking.

In this process the pieces are cuttled in alternate folds with a cotton wrapper, which has been previously wetted-out ; this can be conveniently done by cuttling this wrapper into a shallow water trough and from thence into a scray. Two operatives at the ends of a six-foot table then fold the wet wrapper and the fabric to be shrunk layer by layer, leaving the pile, say, for four hours. The cloth is then taken out and hung over rods in a drying room, which may be moderately warmed. During this drying the cloth shrinks both in width and length. In “ shrinking the operation is repeated and a further smaller shrinkage obtained. The principle «will be perfectly clear from the discussion of wool and humidity in Chapter X. The spinning and weaving both tend to put the fibres into an elongated state ; the tentering, by stretching to eliminate creasing, produces the same effect on the yarns and texture. When the wool has become thoroughly wetted—i.e., when it has taken up water of imbibition, etc., to about 30°%— it is then a plastic gel, and the impressed strains can no longer persist. On drying out, the fibres tend to take up their original form, and a general contraction of the texture follows. All crimps and creases, etc., tend to reappear during the shrinking, and a final mild pressing follows to level up the fabric.

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There are some practical details necessary to the successful working of even this simple process. It is very common to have severe attacks of mildew in shrinking rooms. This is a subject which receives detailed treatment along with the general question of stains and damages, but in this case it may be cured by a periodical chlorination of the cotton wrappers ; this may be carried out either with a weak solution of chlorine gas—commercially procurable as liquid in steel cylinders—or as a sodium hypochlorite solution. The rods in the drying room are commonly of wood, but they are preferably superseded by glass tubes; these are threaded over thin iron piping wrapped with listings, etc. A clean non-staining surface is thus secured. The hand shrinking process is slow, tedious, and of limited output; but it is simple and effective and extremely adapted to high-class worsteds, for the better cricket and tennis flannels, dress stuffs for summer wear, and tropical goods. It is an ideal form of ‘* London Shrinking.” After drying out, the fabrics are given a light pressing, cold or at low temperature, for dispatch.

It will be seen that the theory underlying the water-shrinking process is concerned with two points :—

1. Wetting-out the wool fibre. 2. Air Drying at ordinary temperatures.

The first point has been adequately dealt with in many preceding sections, but the second arises especially in the shrinking aspect and may now be discussed. Quantitative data for evaporation of water from textile surfaces are lacking, and recourse must be made to the results of engineers on evaporation from free surfaces of water itself. From heavily wetted fabrics the data are similar. One of the first results of inquiry is the very great importance of movement in the drying air. A few evaporation curves taken from the work of Box on free water surfaces in still air at various temperatures and degrees of humidity are given in Fig. 97. The enhanced effect at higher temperatures is very patent. Thus, while at 62°F. the evaporation for 70% humidity is very nearly =, lb. per square foot per hour, at 92°F. it is } lb. But shrinking differs from tentering, for example, in that these higher tem- peratures are precluded. A great gain of drying efficiency is possible by the use of air currents. The diagram in Fig. 95 shows the relative increase in the evaporation when the air is in motion. At the moderate velocity of 30 feet per second— very nearly 20 miles per hour—the evaporation is multiplied eight times over the rate for calm air. Plainly, when shrinking is carried out by hanging pieces over rods or when drying of wool is done on the floors of stoves, stagnation of saturated air is to be avoided. The reason is not far to seek ; near the

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wetted surface the air layer has humidity of 100%, or satura- tion and evaporation ceases until this is displaced.

INCREASE OF EVAPORATION IN AR CURRENT

— > FACTOR ° INCREASE RATE ° EVAPORATION

SPEEDS JO FS Fie 95.

tGo EVAPORATION OF WATER (HEATED) AIR AT 52°F. AND 30% HUMIDITY (eox) tooPr he 3-03} <= a ~—S B "| ' ; . °° 40° 30° 120° iGoe 1go* TEMP. FAH.

Fic. 96.

Another diagram illustrates the effect of heating the water to be evaporated, a method inapplicable in the best shrinking, but analogous to passing the fabric over a cylinder machine.

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EVAPORATION OF WATER IN STILL AIR

Fig. 97.

Fie. 98—HEATER anp FAN ror WARM AIR CURRENT. (F. HatrerRsLEY PicKarpD, LEEDs.)

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At a temperature of 180°F., an evaporation of 2 lbs. of water per square foot per hour can be secured under fairly common conditions. A table of the amounts of water in grains per cubic foot at different temperatures and humidities is appended, for the ordinary range of weather conditions in this country :—

RELATIVE HUMIDITY PER CENT. TEMPERATURE. 100 80 60 40 20 40°F. 2.86 2.09 1.72 1.14 0.57 50 4.10 3.28 2.46 1.64 0.82 60 5.77 4.62 3.46 2.31 1.15 70 8.01 6.41 4.81 3.20 1.60 80 10.98 8.78 7.69 4.39 2.20

Fie 99.—PADDING or WEIGHTING MACHINE.

(SELLERS & Co., HUDDERSFIELD.)

MACHINE SHRINKING PROCESSES.

The slow working and limited output of hand shrinking is bound to lead to attempts to speed up the operation by machine methods ; moving plant has been applied both to the wetting- out stage and to the subsequent drying. The dewing machine in its various forms is used to deliver moisture in a fine spray to the cloth, and the steaming box may be called into play to

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aid the rapid, even and general absorption. Another form of machine has rubber-covered rollers rotating at a predetermined depth in a trough having a controlled water level, thus taking up a film of liquid ; a pair of squeezing rollers further regulates the amount taken up. This arrangement may be used to. damp a wrapper which is then wound with the cloth into a roll; the motion is then reversed and the damp fabric piled by a cuttling mechanism on to a scray. A “lecker” is sometimes employed as a_ wetting-out machine. Another rapid method is to steam the cloth heavily on the steaming mill to the stage of wetness ; then dry slowly. Pieces are even run through warm water for the first stage. In the drying stage, a cylinder machine has been applied, having the separate cans gear-driven, so as to put no tension on the cloth. A shrinking routine has been arranged :—Steaming, dewing, steaming and drying on rods.

CHEMICAL SHRINKING METHODS.

These are based on the well-known action of chlorine on the wool fibre. The chemical element CHLORINE has a par- ticularly vigorous chemical affinity for the wool substance ; it is stated that as much as 30% on the weight of the wool can be taken up. Long before this stage, however, the entire character of the wool molecule is altered, the fibre rotting and falling to powder. Absorption takes place from gaseous chlorine or from its solutions, however prepared. In the older systems, chloride of lime was dissolved, the solids settled out, and the clear liquor was diluted and used, with the addition of some sulphuric acid to liberate the gas, as a steeping vat for the wool. This was a defective and dangerous method, though still occasionally practised. A more effective process is to convert the bleaching powder into the very soluble Sodium Hypochlorite by mixing solutions of bleaching powder and soda-ash. This sodium hypochlorite solution is then acidified and employed as the chemical shrinking agent. A modern method, widely used in the hosiery trades, where ‘ unshrink- able’ is a word of great magic, is to decompose solutions of common salt in specially devised electrolytic apparatus. The voltage, current, concentration and time are controlled, to secure a chlorine solution of known content. Another method, devised by the author, was to dissolve chlorine gas—which is purchasable as an ordinary chemical commodity—in water and apply it to the fabrics after scouring in the familiar dolly machine. I The action of chlorine on wool is strongly exothermic, i.e., the reaction produces heat. The wool is eroded, the scales,

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being on the exterior, are first attacked, and the fibre is damaged. The sulphur content of the molecule is largely oxidised, sulphuric acid being formed, and the wool tissue becomes more hygroscopic. Its gelation properties appear to be reduced.

SHRINKAGE TESTS.

These may be made in the ordinary way, by subjecting the garment or test piece to repeated washings and dryings. An excellent, but severe, ordeal is to send measured samples to a power laundry and put them through the machines as many times as necessary, even to destruction. Another drastic trial is to send samples through the milling machine, measuring at intervals and after each run. By these means the relative merits of shrunk goods may be assessed. If there has been over-chlorination—an error of common occurrence—micro- scopic examination of the fibres shows at once the extent of damage to the epithelial scales.

Minor Wet Processes.

It will be convenient to group under this heading a number of operations comprising the action of water on wool, which do not involve any new aspects of the problem beyond those already dealt with in more typical or general forms in the previous sections. Among such are Roll Boiling, Potting, Wet Raising, Steaming, Dewing, etc.

Roll Boiling and Potting.

This process is characteristic of certain kinds of heavy woollen finishes, being applied to fabrics of the super, broad- cloth and faced types ; carriage and furnishing cloths, doeskins, beavers, pilots, etc. The finishing routine is generally on the following lines :—Preliminary knotting and mending, woollen scour of a saponification type ; milling (the shrinkages on the loom setting are often 30-40%); washing down; drying in the stove or tenter ; damp raising ; cutting level and moderate pressing ; followed by roll boiling. The boiling process is intended to produce a bright, glossy finish and soft handle, such as are exemplified in a billiard cloth. It is nearly related to crabbing in both principles and details, and is, of course, productive of a high degree of permanent set. The “boiled finish” is an alternation of raising, boiling, pressing to secure a dense texture and even lustrous surface, the distinctive features of the older “ fine ”’ cloths.

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The fabric is wound on a roll preferably of perforated metal, perfectly smoothly and free from creases and crimps; the process may be used to rid a cloth from already formed crimps. The rolls are then placed vertically in a cistern of cold water, which is warmed up slowly at first and afterwards brought to the boil ; the boiling may be continued 3, 4, or 5 hours. The rolls are then lifted out and allowed to drain and cool while in the upright position, when the operation is repeated, after rewinding with reversal. In some cases, actual boiling is not permitted, a temperature of 160—180°F. being the maximum. The plant for roll boiling comprises a winding-on frame to take the rollers; the old-fashioned wooden rollers were very objectionable on the grounds of rotting, producing wood stains and mildew, loose axles, etc. The boiling cisterns should have a grating at the bottom and a thorough circulation with even heating by the steam must be ensured. The boiling process, badly carried out, is a frequent cause of unlevel dyeings. It is evident from the general similarity to the crabbing operation that boiling is open to the same dangers. Pressure marking, loosely called water marking, i.e., the printing or embossing effect produced on the wool fibre while in the plastic state at the higher temperature, is a common fault, and is due to the same cause as in crabbing, viz., excessive tension in winding on the earlier layers. If the rolls are not properly cooled off before unwinding, crimping at the cuttle edges may result. Uneven heating or uneven draining is apt to put the wool into different states of susceptibility to the subsequent dyeing and the production of shading or want of uniformity of tint. Boiling is a drastic operation, but its effects are those of “ permanent finish ” ; attempts have been made to substitute for it the blowing under slight steam pressure in closed vessels. The routine finish outlined above would be completed generally as follows :—After the first boiling, cool off, reverse and rewind and reboil ; cool again, reverse and reboil; dye up; raise wet; steam and brush; cut level; hot press; steam and brush lightly ; rig and fold. In all roll processes, when the pieces may be placed upright, the slipping of the cloth on the rolls must be guarded against, otherwise, creases will be formed impossible to rectify. Another form of this process winds the piece on the roll through a trough of warm water, a short length of the usual wrapper being interposed. Some pressing and raising or brushing rounds may be given between the different boilings. Actual boiling is not always necessary or advisable, a tem- perature of 185-195°F. being sufficient. The modern forms of crabbing with forced pumping are tending to replace boiling on many goods.

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Dewing or Damping.

This operation, in the old days, was carried out by spreading the cloth in the fields and leaving it exposed all night. A more rapid method consisted in cuttling the dry piece fold and fold with a damp one. Modern methods use machines in which fine sprays or mists of water are projected upon the cloth ; these may be produced by diffusion or by brushes revolving in shallow troughs. Dewing machines often carry a steam box in addition. The other details are feed and drag rollers and cuttle motions.

Fie. 100.—BRUSH DEWING MACHINE. (SELLERS & Co., HUDDERSFIELD. )

The process is simply a conditioning operation. In an extreme form it is used for weighting the cloth, and has been responsible for much mildewing of finished goods when warehoused or exported. Dewing rectifies the ill effects of blowing, removing the papery handle and excessive gloss. It is a necessity in very dry pieces before going to the press, and in this case time should be given for the full penetration to occur before sending forward. The result of hurry under these circumstances is to produce a glazed effect in the pressed fabrics. During the damping process, the cloth inevitably shrinks, especially if there has been much pulling at the tenter; this is the usual result of the partial release of latent strain when wool becomes moister. I

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Brush Dewer. .

a: Drive. B. Passage of Cloth.

RK. we

Fic. 102.—BrusH DEwina MACHINE.

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Steaming.

The steaming operation must be carefully distinguished from blowing or the lustring forms of decatising. Its object is to remove the gloss from the surface of the fabric, together with the thin papery handle—lack of fullness—which results from blowing. The circumstances under which the steam is applied in the two cases are quite different. In the steaming mill the cloth is pulled by rollers covered with drag plush over

Fie. 103.—DOUBLE BRUSH DAMPING MACHINE. WitH ALUMINIUM ROLLERS. (SELLERS & Co., HUDDERSFIELD.)

an open trough, the hollow base of which is finely perforated and is connected to a steam supply. The cloth thus passes over a fog of warm steam, losing its surface glaze and harshness. It should be carried out slowly, “ little steam and many rounds” being the practical finisher’s guide in the matter. In theory, it is one of the many forms of the conditioning principle. Some amount of control over the finish may be

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exercised by running the cloth face or back downwards—or both alternately—over the trough. The effect on the handle is due to the lifting of the fibres from the surface, along with swelling due to the water of regain. Like dewing machines— with which the steaming box is often combined—these steam and water appliances give much trouble with condensations, rusting and drips; stains are frequent and being in the later stages of the finishing are correspondingly annoying. Over- steaming causes the fabric to be limp and flabby ; it is a fatal defect, easily produced in worsteds, while woollens require and stand much more treatment. A minor application of the steaming and brushing machine is to raise the fibre before cutting, so as to get a thoroughly clean surface. Glazed pieces from over-pressing are corrected in the steaming machine. It is often sufficient to follow the steaming by “ cold flatting,”’ i.e., moderate pressing without the application of heat.

Dry Beating. This is a combined process of steaming and raising, and is carried out by a steam box fitted to the raising gig; a per- forated roller supplies the steam. It is intended to secure a greater degree of plasticity in the fibre, with the ultimate idea of developing the definite “draw ’”’ in the pile or cover of surface fibre ; that is, the fibres are made to lie in one direction, e.g., the face in a beaver cloth.

Waterproofing of Fabrics.

The treatment of textile fabrics with a view to resisting wetting or permeation by water, may be carried out in many ways and by diverse materials. The underlying principles are either :— . 1. The coating of the cloth with some resistant substance such as a drying varnish, indiarubber, etc. 2. The impregnation by metallic soaps, solutions of paraffin or other water-repellent bodies, and the like. There may exist all degrees of impermeability up to that of rubber tissue itself ; many of the less effective methods might more justly be described as shower-proofing rather than water-proofing. The physical principle involved is the des- truction of the natural capillarity of the fabric by a deposit or coating of some substance intrinsically resistant to water. It is obvious that a tightly spun and closely woven texture will favour the ends desired, apart from the chemical treatment. Chevreul had noticed that wool, immersed in solutions of alum, absorbed the salt leaving the solution weaker; after washing with water until reagents showed no sulphates what- ever, the dyeing experiments proved that alum or something

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> bi = a oni i ae

a, oe I 4

il (= I le = ts fin a D>

STEAMING anp CRABBING MACHINE.

Fie. 104.—COMBINED

Wm. WHITELEY & Sons, Ltp., Lockwoop, HUDDERSFIELD.

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else remained, which enabled fibres to dye different colours from the untreated fibre. MM. Thenard and Ronard had previously pointed out that wool fixed alum against any practicable washings in cold water. With acetate of alumina they found that the acetic acid escapes on drying, but the alumina thus decomposed remains firmly fixed on the fibre. Stas suggested a dissociation explanation for the absorption of alum, and Havrez confirmed this in dilute solutions.

CHEMICAL THEORY OF PROOFING.

The compounds of aluminium with acetic acid are unstable, having a strong tendency to form basic salts in solution; at higher temperatures they spontaneously decompose, leaving aluminium hydroxide, i.e., alumina, the acetic acid evaporating off. Aluminium Acetate is usually made from Aluminium Sulphate and either Calcium Acetate—grey-acetate of lime, 80°%—or Lead Acetate (sugar of lead). Lead acetate, Pb (C,H,COO), + 3H,0, has a solubility of 1 in 14 of water at less at higher temperatures. Aluminium sulphate, Al, (SO,), + 18H,O. has a solubility of 102 parts per 100 of water—i.e., practically 1 in 1—at 15°C., and 1132 parts per 100 at boiling point.

1. From Calcium Acetate :— Al, (SO,),-18 aq. + 3Ca (C,H,0,),.2 aq. = 667 3 x 194

Al, (C,H.0,), + 3CaSO, + 20 aq. 2. From Lead Acetate :— Al, (SO,),-18 aq. + Pb (C,H,O,),.3 aq. 667 379

Al, (C,H,0,), + 3 Pb SO, + 21 aq. These reactions must be conducted in the cold ; aluminium acetate is known only in solution, gradually decomposing into acetic acid and the basic acetate, a process accelerated by heat. Al +:H,0-—) Al + a0, He On boiling the solutions of this basic acetate, aluminium hydroxide and acetic acid separate. Al (C,H,0,),.0H + 2H,O = Al (OH), + 2H.C,H,0,. A basic Aluminium Acetate, Al (C,H,O,),.0OH + 14 H,O, may be obtained in a crystalline form by cautious evaporation of solutions of the normal acetate at temperatures less than 38°C. ; it is soluble in water. Dilute solutions (4-5%) of the normal acetate slowly deposit crusts of a basic acetate with 2-24 molecules of water, but insoluble in water. In the more elaborate processes, e.g., india-rubber and varnish proofing, special plant is required; in the present chapter only such methods as are practicable in the machines

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of an ordinary woollen finishing department will be described. Of these, the principal involve the employment of Aluminium Acetate with or without soap; in this latter case, the pro- duction of an Oleate of Aluminium on the fibre is the result. The solutions are applied to the fabric when scoured, milled, and squeezed or wrung to dryness as regards moisture ; hydro- extraction leaves the cloth in a suitable state in this respect. Or, while still in the scouring machine, all excess water is run off, i.e., until the pieces are wrung dry ; the proofing solution is then added and the goods run for 15-20 minutes to secure saturation ; if a second soaping solution is to follow, a similar period of running is allowed.

PRACTICAL RECIPES.

There is much variation in the proportions of the ingredients taken to produce the solutions of aluminium acetate; the theoretical amounts are indicated in the equations given above. 1. Dissolve 30 Ibs. Sulphate of Alumina in 80 gallons of cold water, and add 36 lbs. of 30% Acetic Acid. Then stir in gradually a paste of 13 lbs. of powdered chalk in 2 gallons of water. Allow to stand and use the supernatant liquid. 2. Dissolve 100 lbs. crude Calcium Acetate and 700 lbs. Sulphate of Alumina, each separately, to a strength of 5-8°Be. or 7—-12°Tw. 3. Lead Acetate, 564 lbs. is dissolved in 15 gallons of water, and 33 lbs. of Aluminium Sulphate is separately dissolved in 6 gallons of water. The solutions are mixed and the precipitate allowed to settle. Decant the clear liquid and take 5 gallons for 400 lbs. greasy weight of cloth. The second solution is made by dissolving a good white curd soap to a 10% solution (2 lbs. to 2 gallons water); add 2 gallons of this per 400 lbs. weight of cloth. 4. Take 284 lbs. grey Acetate of Lime in 15 gallons of water; also 32 lbs. of Aluminium Sulphate in 6 gallons of water. Mix, and use 5 gallons per 400 lbs. of cloth. Follow as above by 2 gallons of soap, 10% solution. 5. A method of operation by vat working is to mordant the cloth with a solution of Aluminium Acetate for 3-24 hours in the cold ; after whizzing or wringing, the soaping follows, . precipitating an insoluble soap of aluminium and fatty acid. The soap bath is composed of 10-15 Ibs. of soap in 20 gallons of water at 38-48°C. But, of course, the whole process is shortened by running in a machine. for the first solution, equal parts of aluminium sulphate and lead acetate may be used; or, 10 parts aluminium sulphate, 9 parts sodium _ carbonate, and 34 parts acetic acid (50%). In general, the use of calcium acetate will be cheaper than the lead salt ; four-fifths of this salt is acetic acid, or in the

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crude commercial form, say about two-thirds of the weight ; in the lead salt, however, only one-third is acetic acid. The prices of the two compounds at present are :—calcium acetate £31, lead acetate £75 per ton. The efficacy of the proofing process is greatly increased by a thorough pressing, preferably machine pressing or calendering. In certain trials by the drop test, a cloth stood eight minutes after the first pressing, then ninety after the second pressing, and after a third it resisted the test for four hours. After- treatment by waxing solutions or emulsions of soap and waxes may be applied, but as regards proofing of the kind discussed in this chapter they are perhaps hardly worth while. Japan Wax (10-15 parts to 20 soap and 250 water) is used, the soap being dissolved first and the wax added. Or wax-ammonia compositions may be used, with after-fixation by lead acetate.

THE TESTING OF WATER-PROOFING.

The methods of testing fabrics for efficiency of the proofing are somewhat empirical. 1. The cloth must support a column of water 12 inches high for several hours without the passage of one drop. 2. The height of a water column which pierces the fabric is noted.

3. The cloth is made into a bag and the time of percolation noted. In a research on ‘“‘ The Influence of Atmospheric Exposure on the Properties of Textiles ’’ (Jour. Soc. Dyers & Cols., 1920), Prof. A. J. Turner tested a number of fabrics—mainly of a kind used for aeroplanes and airships—for the value of the proofings applied to them.

‘‘ For measuring tightness the funnel test was used, the behaviour being observed of a square piece of 10 in. side folded and placed in a glass funnel, and then loaded with 300 c.c. of distilled water. To pass the specifications for proofed fabrics, the material must not allow any water to leak through during the ensuing 24 hours, nor allow more than a few evenly distributed drops to appear on its underside. Four proofings were tested :—(1) Oil; (2) Cupram- monium ; (3) Basic Aluminium Acetate; (4) Bitumen.”

Prof. Turner comments on the third process, by aluminium acetate, as follows :—

presence of the proofing appears to have no effect on the strength of the fabric ; moreover, deterioration of the unproofed and proofed materials proceeds to about the same extent on weathering, there being no marked deleterious or preservative influence exerted by the proofing. The water-tightness was satisfactory initially and for sometime subsequently, but tended to diminish gradually as the exposure was prolonged. As the proofing was tested on a fairly light duck, it was concluded that on a heavier type of fabric, with possibly some slight modification of the process, this proofing would probably prove satisfactory.”

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A recipe given by the Bayer Co., especially for tent and sail canvas, is as follows :— Fy Prepare acetate of alumina by dissolving separately 15 Ibs. lead acetate in 14 gallons boiling water, and 164 lbs. sulphate of alumina in 14 gallons boiling water. Mix the hot solutions with constant stirring, allow to stand, decant and — ‘filter ; then wash the precipitates and bring the main solution, by means of these washings, to 9°T'w., being now ready for use. 2. After impregnating with acetate of alumina, roll out the goods taut, pass through a soap solution, and dry slowly. 3. Or substitute the soap by the following :—Melt 30 lbs. beeswax and add about 21 Ibs. boiled linseed oil ; boil up, dissolve 20 lbs. resin soap in 22 gallons condensed water, and add to the previous solution. 1 gallon of this mixture per piece.

Staining and Burl-Dyeing.

These processes are intended to deal with the vegetable matters occurring in wool, in cases where it is not feasible to remove them by other operations, e.g., carbonising. Broadly speaking, carbonising would be applied when an all-wool fabric is required. But cotton enters largely both as admixture with natural and recovered wool into yarns, and also separately as both warp and weft ; it is then sometimes desirable to dye up the cotton to procure a level shade or for effects. In the case of Speck, Burr, or Burl dyeing, the “‘ shives ”’ or particles of vegetable tissue—seed-capsules, plant-hairs, and fibres of a cellulose or lignin composition—are present in some wools to an extent impossible of removal by the ordinary method of hand picking. Such wools may be used in certain goods if these vegetable elements are coloured up to the general shade of the fabric. As they do not take the dyeings of the wool, separate treatment is necessary. Again, the goods on which the staining process is most utilised are often wholly composed of cotton and recovered wools ; such materials could not bear the expense of separate dyeing operations, and the staining in the scouring, rinsing, or milling stages without the employment of other machinery leads to great economies. An excellent summary of the historical development of the Direct Cotton colours will be found in the brochure of the Bayer Co. on the Benzidine Dyestuffs, 1910. The early coal- tar colours did not dye the vegetable fibres directly ; tartar, tannin, etc., were used as mordants. Later came the Alizarin type, requiring mordants on all fibres. In 1884, Congo Red, the first dyestuff dyeing unmordanted cotton an intense colour, was discovered ; it is stated that it had been noticed to stain filter-papers permanently. Investigations following year by

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year have now developed a large class of Congo, Benzidine, Substantive, or Direct Cotton colours, with the distinctive property of application to cotton without mordants. They are fairly fast to washing, and may be used from neutral, faintly alkaline, or alkaline baths ; in rarer cases from an acid bath. Structurally they are “‘ azo ”’ dyestuffs, largely produced from intermediates based on naphthalene. The great solubility of these dyestuffs leads to easy working and ready deposition on the fibre; on the other hand, under certain conditions they are liable to bleeding or running. They dye well-on mercerised cotton and on some artificial silks. Some of the class are applicable to wool at higher temperatures and from an acid bath, and many are particularly applicable to self shades on union goods by variation of the assistants and temperatures. The dyeing of cotton with these colours is simply a matter of ensuring contact under the most favourable conditions :— control of temperature, choice of assistants, etc.

ADJUNCTS OR ASSISTANTS.

Among these are Common Salt, Glauber’s Salt, as accelerators, fixing the dyestuff upon the fibre by diminishing the dissolving power of the solution. Soda-ash, Na,CO,, in moderate quantities of 2-3°%, has the opposite effect, promoting levelling ; soap has a similar general effect. salt is perhaps most generally employed in quantities of from 5-10% on the weight of the cotton, the heavier shades requiring the greater quantities and the higher temperatures. It is sometimes advantageous to add a further proportion of salt half-way through the run. A little soda is added against possible hardness to a bucket of warm water and the dyestuff added, allowing from 8-16 ozs. per piece, according to the weight of the cotton ; the goods may be run for half-an-hour orso. The washing-off or cold running need not be prolonged ; in some cases it may be omitted ; in others, further salt may be added at this stage. The volume of liquor employed should generally be greater for the lighter shades. Drying-off on the tenter should be carried out as soon as possible, to retain the level shade. I

AFTER-TREATMENTS.

In the present methods of staining in the scouring or milling plant, not much can be done to secure greater fastness by additional manipulation. A simple process is to give the goods a 15-20 minutes’ run in Copper Sulphate solution 1-3°% on the weight of the cotton, together with a little Acetic acid ; this forms a copper lake on the fibre, with improved fastness

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to both light and washing. Salt Blacks are improved by a 2-3°% solution of Formaldehyde. As a rule, direct cotton Black, Brown, Blue and Green dyestuffs, with their combinations, will meet all ordinary requirements ; the Black is in general use as a groundwork, and especially for heavy shades. Blue blacks may be saddened by a little Brown, and generally there is a little scope for judgment in these joint dyeings. Pieces may be stained in the “ lecker,” during scouring, before throwing off for wringing and milling, and when washing off after milling; if for acid milling, they may be stained beforehand in the washing machine taking care that the washing is thorough. Plenty of water should be used in the machine. If the amount of cotton is small, say 5% or so, then 1 oz. of Black, or 4 oz. Black and 4 oz. Blue, per 100 lbs. greasy weight will be sufficient; the colour may be dissolved in boiling water, about 2-4 pints, allowed to cool, and diluted with 1 gallon of cold water before adding to the machine. For heavy staining, 1-2% is often used.

BURL DYEING.

As practised in the scouring department, this is in principle simply a process of ink-staining the vegetable elements by a Tannate of Iron formed on the fibre. The fabric, say three pieces of average weight, is first run for an hour in a tannin solution, e.g., Extract of Myrabolans 40°Tw., about two buckets ; this is followed by a 25 minutes’ run in Iron liquor, one bucket, after which the pieces are swilled off, and finished with a round of fuller’s earth. A formula for Inking Solution is as follows :—

Bath I. Haematine Crystals (logwood) 15% Soda Ash I 2% Bark Extract (quercitron or myrobalams) 2% Turmeric 2% Bath II. Copperas (Ferrous Sulphate) 15%

The solutions are not exhausted, and if in different vessels

may be renovated and used repeatedly. *

* * * * * * *

Steaming is generally combined with brushing; the joint physical and mechanical operations are directed to the same end, viz., the raising of loose or extra long fibre from the surface for cutting away, or the securing of evenness in the nap and a level finish. Brushes for textile purposes differ in their requirements, and special knowledge is necessary in their selection. Usually bristles are denoted by their country of origin :—Russia, Siberia, India, China, etc. ; they are gathered after shedding from the skin of the boar, and undergo sorting,

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picking and packing. Brushes have many functions in textile machines. In the cutting machines it is usual to raise the nap by good brushing. The bristles must be of equal height, not too soft, as these do not penetrate; on the contrary, they must not be too hard, as these act like raising points and pull fibre from the yarns. The general rule is to use harder brushes _where the cover is deep and soft brushes for closely-cut cloth, especially just after steaming. The brushes of a shearing machine should be reversed frequently, say, every three to four months; thus any tendency to permanent bending of the bristles will be corrected. Worn places in brush rollers may cause stripiness in the cloths. It is not generally known that a brushing round can be substituted for the process known in dress face finishing as ‘“ washing-off-gigging,’’ where worn teazles are used, along with copious flushings of cold water, to clean away loose dyestuff, flock, scum from the boilings, etc.. Brushes are made specially for this operation, to resist the moisture. It should not be necessary to remark that brushes require cleaning, like other parts of textile machinery.

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THE RELATIONS OF AND MOISTURE.

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CHAPTER X.

The Relations of Wool and Moisture.

There can be no subject of greater intrinsic importance in the industry than the relations between wool and water, whether it be in the state of liquid or vapour, or as steam. Indeed, in this connection, the wool manufactures are a branch of applied physics in as real and complete a sense as the dyeing trade is a branch of applied chemistry. On the commercial side, “‘ the conditioning ” or regain standards are essential in market transactions. Wool in the various forms of raw material, scoured wool, combed tops in oil or dry, noils, yarn in oil or scoured and fabrics, varies very greatly in its cont2nt of moisture, and it is therefore necessary to standardise the ‘ condition ”’ figures for trading purposes. From a lot of wool fibre in any given state samples are taken and the dry weight found by heating these in air at 230—240°F. for $—3 hours until constancy of weight is obtained. On the scientific aspect of this matter there are some points which arise; it plainly reaches an equilibrium of vapour pressure in the wool with that of the air supply, and this is a quantity requiring exact definition. But it is sufficient for commercial needs. The difference of weight before and after this operation, expressed as a fraction or percentage after drying, is termed the REGAIN ; it represents the amount of moisture in the wool when in equilibrium with its environment under the original circumstances.

Example.—Suppose a one-pound sample of combed top in oil to lose 3 ozs. on drying out. We have :—

Original weight = 256 drams. Loss in drying i Me Absolute dry weight = 208 _,, I . Loss on drying 48: X 100 and the Regain = a xX == =

23.1%.

AA

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The official standards of the Bradford Conditioning House are :—

Scoured wool 16% regain Tops in oil- 19 Noils 14 Tops dry 184 Yarns, dry or oiled 18 : Cloth 16

In the example above the excess regain is 4.1%. The official standard would be 119 units, the actual sample shows 123.1 units, and would be appraised accordingly in the commercial transaction.

On Atmospheric Humidity.

If a drop of water is introduced at the base of the column in an ordinary barometer it will rise through the mercury, and on reaching the vacuum at the top will be immediately vapour- ised ; the column of mercury will be slightly lowered by the pressure of the aqueous vapour this formed. Further drops will behave similarly until a saturation depending on the existing temperature of the space above the mercury occurs, when some water persists as a liquid layer on the top of the mercury and depression of the mercury column remains constant. ‘The vapour pressure of the water at the temperature prevailing is measured by the depression of the mercury column; it varies with the temperature. Now evaporation similarly takes place into the atmosphere from water surfaces at all temperatures ; the saturation or maximum vapour pressures for a number of temperatures are given below :—

ABSOLUTE ABSOLUTE TEMP. C. VAPOUR PRESSURE TEMP. C. I VAPOUR PRESSURE cms. cms. 0.46 I 60 14.88 10 0.92 70 23.31 20 1.74 80 35.46 30 3.16 90 52.54 40 5.49 100 76.00 50 9.20 105 90 . 64

The actual amount of water vapour present in the free atmosphere obviously depends on the moisture available as well as the temperature ; it may, as in misty weather, reach the maximum possible at the temperature, and at other times be relatively dry. As a rule, the air contains less than the saturated value and the ratio of the vapour pressure existing at any time to the maximum or saturation value for the prevailing temperature is called the RELATIVE HUMIDITY. Our sensations as to the dryness or dampness of the air depend on this ratio and not on the actual quantity of water vapour present in the air. So also does the absorption of a mass of

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371 wool fibre. In England the average circumstances in summer may be assumed to be about 70-75% relative humidity and a temperature of 60°F. This would give about 16% regain on wool, while 100% humidity might give about 30%, according to the temperature. In the United States the figures would be about 65% humidity at 70°F. In India the average relative humidity is not higher than 20%. Air which is completely saturated at a certain temperature is about threequarters saturated 9°F. higher, one-half saturated 18°F. further, and one-quarter saturated about 27°F. higher in temperature. In this country the air is never less than 25°, saturated, and in winter it is frequently completely so. At humidities over 85% it feels very damp and below 50% very dry. Wool in ordinary surroundings is never below 10°% regain. Thus the atmospheric pressure at any time is the sum of the pressures due to the air alone and the water vapour :— P Pp air op p aq. vap.* P,” the whole pressure, oscillates about the value 30 inches of mercury from 29-31; the component due to water vapour within the ordinary range of temperature, e.g., 32-80°F., varies up to about 1 inch of mercury. A general table of humidity, etc., is appended :—

RELATIVE ACTUAL DRY BULB. WET BULB. HUMIDITY HUMIDITY: MOISTURE IN % GRAINS/CU. FT. I GRAINS/CU. FT. 32 — — — — 35 Bs 80 1.9 — 40 38 84. 2.4 2.86 50 48 86 3.9 4.10 60 58 88 5.1 5.8 65 63 88 6.0 6.82 70 68 88 bok 8.07 15 714 814 7.4 9.08 SO 754 774 8.55 11.03 85 79 12 12.78 90 83 69 10.3 14.92 95 87 66 11.5 17.42 100 9] 64. 1257 20 The limits in the table are those of the Factories Act for humidity.

When the atmosphere is saturated with water vapour at a given temperature, further evaporation from wetted surfaces ceases. If the temperature now rises, the capacity for holding aqueous vapour is increased and further evaporation ensues ; if, in the contrary, the temperature is reduced from that appropriate to saturation, then condensation of some of the

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aqueous vapour follows and dew is deposited. Hence the function of wet and dry bulb thermometers as indicators of atmospheric humidity. The rate of evaporation is determined by the relative humidity of the air and the evaporation causes a cooling of the bulb. From the difference of the readings the relative humidity may be ascertained. At an average tem- perature of 60°F ., 2 degrees of difference between the wet and il bulbs indicates that the air is damp; 10-15 degrees very ry.

SOME DEFINITIONS.

DRY CONDITION is that of a material which has reached a standard weight in a drying oven at 105—110°C. MOISTURE REGAIN = R, is the difference between the weight of the material in a normal and dry condition expressed as a percentage of the dry weight. pir 100:(W

Wo MOISTURE CONTENT = C, is the same, but reckoned as a fraction of the normal weight. hie 100 (W — W.,) Wo STANDARD CONDITION is that of the agreed official standard.

DIURNAL VARIATION ust OF REGAIN [HARTSHORNE] rT Ww 3 [st 7 <a 2 3 “6 PM, —_—— > TIMES Fig. 105.

In order to give some idea of the variations which a sample of wool may undergo in different atmospheric conditions, the following experiment, due to Hartshorne, is quoted :—A skein of yarn was prepared, the absolutely dry weight being taken. This was hung up in an open shed protected from the sun and rain, but with good ventilation, so that it could be considered as fairly representing the outdoor conditions. Its weight was then carefully taken and recorded ten times a day at approxi- mately equal intervals for every day in the year, except Sundays and holidays, for a period of one year from May Ist, 1895. A record was also kept of the temperature and relative humidity from the readings of the wet and dry bulb

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do

373

"0

To

Teme’

O 2o 4o 60 60 too Time In MINS,

Fie. 106. HEAT PENETRATION CURVES,

100

80

60

gl

is 20 35 Fia@. 107. VARIATION OF REGAIN WITH TEMPERATURE.

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thermometers. The variations in the weight of this skein were remarkable, ranging from a little over 7% to as high as 35% on the original dry weight. There were occasional variations of 15 or even 19°% in 24 hours. The Bradford Conditioning House many years ago also carried out a comprehensive series of exposure tests on fifty samples of wools and hairs in a public park, daily readings of weight, temperature and relative humidity being taken for two years. It is, of course, desirable that the adopted standards shall be approximately the average condition for the given material, and that deliveries be made as near as possible to the standard. A standard widely divergent from facts indirectly encourages conditioning, the evils of which are well known.

TABLE OF WORSTED REGAINS FOR VARIOUS TEMPERATURES AND DEGREES OF HUMIDITY.

ee 60°r 70°r, I I 90°r. I 100°r. IS eee 10 8 8 50 I 33.8 I 13.2 I 12.6 I 12.1 60 16.7 16:6 I 14.9 I 14.4 1 19:8 70 JO (Gees 80. I 90:9 I 02°) 10.4 18-7 18.9 90 23.5 22.7 I 21.8 I 21.1 I 20.9 I 20.8 100 I 9 7.1 I 26.2 I 25.4 I 24.8 I 24.7 I 24.6

(Based on Hartshorne’s tables.) ABSORPTION OF ATMOSPHERIC MOISTURE BY WOOL.

(ALLISTER M. WRIGHT.) The following tables show how closely wool responds to changes of humidity in the surrounding medium :— GREASY WOOL.

TIME IN HOURS. PERCENTAGE RELATIVE GRAINS/CUB. FT. OF WATER. HUMIDITY. 24 24.38 80 3.6 32 29.27 85 5.2 48 29.77 85 4.4 72 28.82 72 3.8 144 28.66 82 3.9 168 26.62 76 3.8 192 27.56 85 3.8 216 25.70 70 2.7 290 24.85 65 4.3 PURE WOOL. 24 18.03 72 3.8 96 19.50 82 3.9 120 18.70 76 3.8 144 19.62 85 3.8 168 18.47 70 2.9 192 . 18.19 65 4.3

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The author states that wool fat spread upon a watch-glass

absorbed up to 17.2% of moisture.

In all cases the wool

absorbed more moisture when the foreign fatty matter was

removed. ABSORPTION OF oo MOISTURE BY PURE WOOL oft 130% 1921 \/9% 18-3} 170% Gs oO A> 1IB-4} / . eS, ; O5% : a ‘ 25 40 30 120 1GO 200 240 230 she HOURS Fic. 108. ABSORPTION °° MOISTURE ° CREASY WOOL 30% 29%} 26% + 4 75% pa 9 4 CX 26%} 65% ul 25% 5 40 30 120.160 800 “= 60% HOURS

Fic. 109.

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FOREIGN FATTY

376

PERCENTAGE MOISTURE

PERCENTAGE MOISTURE

MATTER. ABSORBED IN PRESENCE ABSORBED IN ABSENCE OF FATTY MATTER. OF FATTY MATTER. 2.06 10.70 11.07 2.16 9.38 9.92 2.60 9.22 9.98 2.88 9.98 10.18 3.28 11.13

Nevertheless, it is a fact that the official standard for tops in oil is 19, as against tops dry, 184. On the diffusion hypothesis of regain set forth later in this chapter, it is easy to see and would be expected that pure wool is more absorbent and follows changes more rapidly than greasy fibre. Wright’s results show that regain is dependent on the relative humidity and not on the absolute moisture content per se. The facts regarding the retention of alkali, etc., in wool, and the con- sequences in respect of sorbing capacity, will account for many seeming anomalies found in tests on greasy wools, scoured yarns, samples of cloths, and the like. In the paper by Shorter and Hall, it is shown that the effect of oil is not specific, but only that due to mere loading of the wool with a non-hygroscopic substance. But it must be noted that wool grease and olive oil are very different in this respect. _ It appears therefore that wool is hygroscopic, i.e., it is capable of attracting and absorbing water—either from the liquid or in the state of vapour—and incorporating this in form or other in its own substance. The state in which this captured moisture exists in the wool substance is an important subject of technical enquiry. When a substance such as Sulphate of Soda, Na,SO,, takes up water from an anhydrous condition, the sorption follows a variation re- presented graphically in Fig. 110.

Along OA there is dry sulphate of soda. Along AB there are three phases at constant pressure, viz., (1) Na,SO,, (2) Na,SO, 10H,O, and water vapour. Along BC the water vapour pressure increases, but there is no sorption, and hence there are the two phases water vapour and the salt with ten molecules of water of crystallisation Na,SO,, 10H,O. Along CD this compound exists as saturated solution with the aqueous vapour; and unsaturated solution and vapour may coexist along DE. These discontinuities, however, do not occur when a colloid body like wool takes up water. The process is repre- sented by a smooth curve, indicating that there is no formation of definite compounds. The sorption of water by wool is also a reversible process, in so far as if the atmosphere becomes drier, the water is released in whole or in part, according to the circumstances, i.e. :— 1. As to the amount of water in the wool. 2. As to the amount in the atmosphere.

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We have thus a continual interchange and effort to establish an equilibrium between the wool and the surrounding medium. There are two principal cases :— 1. Sorption of aqueous vapour, usually from the atmosphere, i.e., gaseous sorption. 2. Sorption of water from the liquid state, i.e., immersion sorption. Like many colloids, wool which has absorbed water to a maximum from the atmosphere is then, when placed in water, capable of taking up a further amount. (But see later.)

PRESSURE

oO

ABSORPTION

SODIUM -SULPHATE AND WATER NWAPOUR

Fia. 110.

Consider first the taking-up of moisture from a gaseous medium containing water vapour, in general the free atmosphere. The amount absorbed or REGAIN is dependent primarily on :— 1. The available moisture as expressed by the Relative Humidity, or Mass, per Unit Volume of air, or the Pressure of Aqueous Vapour at the time. This is the most potent factor.

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2. The Temperature. In the ordinary variations of weather conditions this is of minor importance, but in . technical operations, the effect may be very great. 3. Other factors, e.g., state of the wool substance as regards previous history, cleanliness or presence of foreign matter, grease, acids, etc.

2 COTTON — WOOL SO ene E A a {i --= 2 7 (4 — HARTSHORNE < i ul £7 rq REGAIN % Fig. 111,

GELATINE

HUMIDITY

CONTENT

Fie. 112.

If a quantity of wool is immersed in a mass of liquid water, ample in amount, it absorbs the liquid, and as is usual in colloid substances, swells up in the process to a limit, the sorption continuing beyond that for the atmospheric regain. In this case, the wool eventually reaches the “ gel ” or swollen hydrated colloid state. In the words of Justin Mueller, it is a turgoid or has become turgescent. When colloid substances are treated as here described and sorption of water follows, the general nature of the process is graphically represented below:— There is plainly a generic likeness in these sorption curves. As Schloesing remarks, ‘‘ Toutes les courbes ont meme allure

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The graphs show double curvature or are of a sigmoid type, and there cannot therefore be a simple and similar kind of water absorption going on throughout. It is further apparent that the sorbed water is not all of the same nature in the colloid, and this very important aspect of the matter may now be separately discussed.

STARCH [FARROW AND SWAN]

> RELATIVE HUMIDITY

WATER PER lOOcRms DRY MATTER

113:

The moisture absorbing power or power of taking up ‘regain’? may be shortly termed the HYGROSCOPIC CAPACITY of the material. In the case of wool, it does not vary very much with the wool quality, nor with the state of aggregation (wool, tops, yarn); but variety of treatment may ©

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affect the hygroscopic capacity greatly, e.g., methods of scouring and drying and finishing operations. For example, Shorter states that the pressing process can alter the regain by as much as 3.5%. Like all colloids, the pre-history has a great effect on the properties. The general outline of the sorption of water by wool is somewhat as follows ; the first portions are taken up by direct molecular attraction, and this is accompanied by a com- paratively large evolution of heat. (See section on Physics of Wool Fibre.) The vapour pressure of the water in the fibre at this stage is small and increases very slowly with the water content. As the sorption continues, the development of heat diminishes and the vapour pressure increases more rapidly, but as the saturation value is approached the rate of increase of vapour pressure falls off, At the actual saturation value the process resembles an osmotic absorption of water by a dilute solution. During these stages, there is a concurrent swelling of the wool tissue; in its ordinary state it may be described as a dessicated gel, at saturation it is characteristically colloidal. The question of the “ saturation value ”’ is discussed more fully later, but it may be here stated that there are great difficulties in determining a maximum sorption, the experi- mental conditions in environments of 100% humidity being rather complex. Besides the phases of moisture in the external air and in the wool, there is a third phase in the adsorbing layer at the surface. It seems certain that the fundamental process concerned is a diffusion, but the exact conditions are not fully worked out. Suppose a mass of wool to be immersed in water sufficiently to reach maximum swelling. If this be now removed, the water in the mass may be regarded as held in the following ways :—

1. INTERSTITIAL WATER,

held in the minute channels between the fibres. Mechanically entangled. A good deal of this may be drained away by gravity, and Vignon, experimenting on cotton, found the following results for 100 parts of fibre, after simple gravity

draining :— Water 497 NH, aq. 2% 509 Alcohol 514 Common Salt 0.9% 522 Benzene 506 Common Salt 17.5% 551 HCl 35% 482 Common Salt 26% 586

or approximately five times its own weight of liquid. Simple squeezing of such a mass gets rid of additional water. Indeed, this moisture is that which in practice is expelled by the mangle or centrifuge, though, as will be seen later, water held in other ways is also removed by mechanical pressure.

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A quantity of wet sand holds its water principally in this way ; the major part of the water of a sponge or peat is of this kind. Practical determinations of the amount of water retained after mechanical expulsion vary greatly ; obviously the thoroughness of the centrifuging will make great differences. Some experi- mental figures from a paper by EH. A. Fisher are appended :—

CRITICAL MOISTURE

KIND OF MATERIAL. CONTENT. MOISTURE EQUIVALENT. Heavy clay subsoil 21.0% 55.1% Silty soil 14.8% 31.0% Quartz sand 4.6% 2.4% Garden soil 24.0% 24.0% Wool fabric 31.0% 53.3%

The moisture equivalent is the figure obtained after long centrifuging at 1000 times gravity; it is patent that in a merely porous and non-colloidal substance like sand, mechanical means will drive off most of the water, but colloid bodies retain large amounts.

The ‘‘ critical moisture content ’’ is the value at which the rate of evaporation of this retained water begins to fall off from constancy, i.e., from the rate appropriate to a free surface. A further series of speeds and amounts retained is here given :—

CENTRIFUGAL FORCE RECIPROCAL OF WATER RETAINED AS + “@q,” CENTR. FORCE % OF DRY WEIGHT. x 100,000. 450 202.0 62.61 825 121.2 51.20 1200 83.3 44.94

It seems therefore that both in wool and cotton the limit of removal of this mechanically-held water lies at about 45-50%. Above this all merely entangled water will be expelled, but water held by other means will be only partially, or not at all, removed. (See also section on Centrifuge, Mechanical Drying, etc.).

A fine-grained sponge holds about 30 grams water per gram of sponge, and a coarse one only about 6 grams.

2. SUPERFICIAL OR FILM WATER

carried on the surface of the fibre as a liquid layer or film. This may be ‘ wetting-out ’’ water held by surface tension, but there is certainly on wool in ordinary circumstances a film of moisture, due perhaps to adsorption, continually present and varying with the humidity of the atmosphere. In the tables and curves from the results of Allister M. Wright, it will be noted that the regain in wool follows the external humidity, and in washed wool very closely indeed. Compare further the

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curve of mean diurnal change from Hartshorne’s figures. A portion of such a film may be removed by the pressure of I severe centrifuging, but not all. Some interesting data for films of water were obtained by Griffiths in a study of hygrometric apparatus, who found that dew films produced on surfaces from the breath, etc., were of the order of 1.2 ten-thousandths of a gram in weight per square centimetre ; the thickness of the films was probably of the order of one ten-thousandth of a centimetre. The vapour pressure of a superficial film is that of pure water itself, and evaporation will take place from it as from a free liquid surface. This statement, however, is true for thick films only. When a film gets very thin, e.g., a few molecules thick, the vapour pressure and rate of evaporation are not comparable to that of water in bulk. It would appear that such a film is renewed or thickened by processes of condensation—or perhaps better, adsorption — from the moisture of the atmosphere. On the other hand, it is susceptible to diffusion into and from the internal water of the wool fibre. This process of inward and _ outward DIFFUSION is evidently the controlling phenomenon in respect of the relations of Humidity and Regain or of Regain and Time at constant humidity. It will be fully discussed in a later section.

3. IMBIBITIONAL WATER,

that is, in the sense here used, water which has penetrated the tissue of the wool fibre and has caused swelling of the wool substance ; this is essentially colloidal water, forming part of the swollen gel. This is renewed or depleted from the super- ficial water by diffusion. The exact description of this kind of sorbed moisture depends upon the view which is taken of the structure of the gel. It might be described as capillary water, if it is supposed to be retained in the minute intra-cellular pores of the wool tissue. Some writers who assume a reticular structure for colloidal gels, term this the vesicular water. If these micro- scopic channels are of sufficiently small diameter, secondary factors such as curvature of surface, tensile strength of water, etc., arise which modify the physical properties as regards evaporation, diffusion, vapour pressure, etc., very considerably. Substances like quartz sand or glass wool possess no water of imbibition, and in certain liquids, e.g., xylene or toluene, the colloid textile fibres (wool, cotton, silk, etc.) show no imbibitional property. Reckoned on the total volume of material and water, the process of imbibition in anhydrous material is usually accompanied by an initial contraction, but later the swelling may be enormous, as in gelatin, many

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hundreds per cent. In wool, it appears to reach a maximum at 30-40% of the primary volume. It is known in the works and is familiar in microscopic practice that imbibed water swells up the wool fibre; there is an actual distension of the wool tissues. An elementary calculation shows that a 15%

increase of diameter corresponds to about 33% increase of volume.

5. CHEMICAL WATER OR WATER OF HYDRATION.

Some part of the water is present in the colloid in more intimate combination with the substance, exerting no vapour pressure. It possesses a strong affinity with the molecules of the wool substance, an affinity requiring active agents or vigorous reactions to destroy the union. It is perhaps more analogous to the water of crystallisation of an ordinary chemical salt, e.g., CuSO,. 5H,O, and its removal often causes profound changes in the material which may then be unable to resume the normal colloidal state. It is the residual water when the process of drying out is being carried to an extreme. LExperi- menting on cotton, Nelson and Hulett heated the fibre in a high vacuum for some hours and condensed the extracted moisture in a Dewar vessel standing in solid Carbonic acid gas, with the following results :—

TEMPERATURE. PERCENTAGE OF WATER FOUND. 5.49 122 I 5.55 155 5.57 184 5.63 218 5.74 238 6.11

Similar experiments by Woodmansey on heating conditioned

wool at a constant temperature of 150°C. gave the subjoined data :—

Loss on heating 1 hour 13.84%

After heating 4 hours 0.21% more 9 7 9 0.12 9 29 12 2? 0.11 29 fn 5;

Total ‘ee in 22 hours 14.36%

The absorptive properties of the wool were found to be impaired, both for water and for sulphuric acid, and the loss of water was accompanied by evolution of ammonia and_ oxidation of the protein sulphur of the wool, the wool becoming more acidic. Part, if not most, of this change is due to some chemical decomposition of the wool. Complete dessication and nothing but dessication is extremely difficult to bring about in the case of organic materials like wool, e.g., the last

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item in Nelson and Hulett’s table above, and involves some chemical break-up. Complete dessication, however, does change the plastic properties of clay and would probably have a similar effect on wool and other colloids. (See Mellor, Trans. Far. Soc. 17, 1922, p. 363.) There is a further detail which proves that the water under consideration is of a special type ; the initial wetting of the wool is accompanied by an evolution of heat, but this thermal change is not now deemed so dis- tinctive of chemical action as formerly.

SUMMARY OF SORPTION. I

Now a textile fibre such as wool in mass ordinarily contains all the forms of sorbed water coexisting in various amounts, according to the environment and previous history. Thus the wool of a test sample in the conditioning oven has chemical water only ; the dried fabric warm from a tentering machine, chemical water and some (perhaps 5-10%) water of imbibition, while wool from the squeeze rollers of the wash bowls has all the forms and the superficial and interstitial kinds in excess. In what ratio do the several types of water exist in or upon the fibre? It is only possible to give an approximate answer to this question, and it is remarkable how little experimental work has been done in the case of wool. There may obviously be large variations in the amount of suspended or mechanically held water. It is commonly supposed in the works and is probably roughly true, that a scoured piece dripping from the machine weighs twice as much as the dry figure, i.e., before squeezing or centrifuging, a wet piece will be twice the ware- house weight. But Scheurer gives the maximum of water absorbed from a saturated atmosphere—i.e., the ‘‘ hygroscopic coefficient :—

28-29.8% for silk. 19-20 .2°% for cotton. 33 .3-35.3% for wool.

And Kimura found from a saturated atmosphere :— 25 .2-28.7% for wool. 19.8-20.0% for cotton.

Some evaporation experiments by E. A. Fisher confirm the conclusion that wool holds over 30% of water other than that removable by pressure; at 31% his observations showed a change in the rate of evaporation. Again, all observers of humidity-regain data obtain curves tending to maximum values at about 30% of moisture. There is another mode of estimation which is interesting :— Consider a wool fibre of 1/1000 inch diameter = 0.001 inch. Its volume as a cylinder V, = 0.7854 x diameter x length = 0.000,000,785 cu. ins. per unit length. If this solid cylinder

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385 swells on immersion in water to a new diameter, say 10% greater (a figure roundly warranted by measurement), then the new volume :— V = 0.000,000,950 cu. ins., and the increase of volume due to swelling is 0.000,000,165 cu. ins., i.e., approximately one-sixth or 16%. If all this increased space is assumed to be filled with water, we have :— (N.B.—One cubic inch of water weighs 0.036 lb.). Weight of water taken up = 0.035 x 0.000000165 = 0.000,000,0059 lbs. and the weight of the wool fibre was = 0.000,000,0380 lbs. Therefore the water approximates to 16% of the weight of the wool. If the fibre had possessed the prior standard regain of 184%, there would be a total of 34%, which is in general agreement with the results above. On cotton, Masson and Richards found 17.7% of adsorbed moisture in an atmosphere of 97% humidity ; by extrapolation, there would be 21% at 100% humidity. In a mass of scoured wool or cloth, assuming the practical rule of total water = double dry weight, i.e., there is 100% wetting, the distribution of moisture might be roughly as follows :— Mass of dripping wool = 100% water. After ordinary centrifuging = 50-60 __,, After severe centrifuging = 45 Superficial or film water = 10 we - Imbibitional or gel water == OG i Chemical or hydrated water = 3-5

But it must be remembered that experimental work is badly required in this direction.

RATES OF SORPTION.

There is another aspect of the WOOL-MOISTURE PROBLEM further than that of the amount of sorbed water under various conditions, viz., the RATES of SORPTION ; in the converse aspect, this means the RATES OF EVAPORA- TION or of DESORPTION. Both are of manifest technical importance, but even less research has been devoted to the time laws of regain than to the quantity relations. In the author’s “* Scouring and Milling, 1921,” there were reproduced four graphs :— Fig. I. Time-Sorption curve for Wool and Water. Fig. Il. Time-Sorption curve for three wools. Fig. III. Time-Shrinkage curve of Milling of a wool fabric. Fig. I1V. Time-Sorption curve for Gelatin-Water.

BB

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TIME - ABSORBTION CURVE FOR WOOL WATER. AIR EXPOSURE]

Ws

I Fie. Tid, I TIME - SHRINKAGE CURVE FOR WOOLLEN CLOT,

Si. — WIDTH

LENGTH

Ts

Fie. 115.

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387 and attention was drawn to the general similarity of these curves.

It is plainly desirable to investigate the time relations of sorption of water further. The writer owes the following experimental results to the Bradford Conditioning House (Mr. EK. H. Townend).

A wool top was exposed in a cabinet of 100% humidity and weighings taken at frequent intervals. From these the

-REGAIN-TIME. CURVE; WOOL TOP.

Gt g a c ¢ oO ei uy +t & © 4 Ly / 3 YS ov a od Q be YQ es 2) QO a ob Q i A i A ° 4 oe 12 6 20 —_——> % REGAIN Fic. 116.

percentage regains were obtained. The dry weight of the sample was 48 grams; when finally taken out of the cabinet it was 58.74 grams, a regain of 22.375%, which occupied 23 hours. After this it was exposed to a dry atmosphere of 47% relative humidity, and in 24 hours had dropped to 10.62%. The curves plotted from these data are given in Fig. 116, and it now remains to determine the law.

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NUMBER OF _ TIME ee N I DEFICIT a a 1 a x% —— log —— |K=—log EXPERI- |IN + HRS. ann oa a—x ie a—x t healt MENT. ] 1 §.25 17..75 1.296 0.1126 .0489 2 Z 8.17 14.83 1.551. 0.1906 0414 3 a 10.10 12.90 1.783 0.2512 .0330 4 4 81.72 Li 29 2.041 0.3098 .0346 5 5 13.00 10.00 2.300 0.3617 .0314 6 6 14.40 8.60 2.674 0.4271 .0309 7 7 15.17 7.83 2.937 0.4679 .0290 8 8 16.10 6.90 3.286 0.5096 .0277 9 9 16.92 6.08. |: 3.783 0.5778 .0279 10 a 17.56 ' 6.44 4.228 0.6261 0272 ll ll 18.29 4.71 4.879 0.6883 12 12 18.85 4.15 5.542 0.7437 .0269 13 13 19.60 3.40 6.7650| 0.8837 .0295 14 14 20.25 2.16 8.364 0.9224 .0286 15 46 22.38 0.62 — — —

The maximum value assumed is a regain of 23%. The average constant for the results 5 to 14 inclusive is 0.0286, and the law over this range is :—

1 23 es iat in= — .0286t) ; jo 0859 Reo or oe 23 (l—e

The same top, dried out in an atmosphere of 47% humidity, gave the following results :—

LOSS OF

TIME a a Ne @ I ACTUAL IN } HRS. ere ne guy log a—x a \—x| REGAIN. ] 2:47 8:53 1.290 0.1106 .0480 22.38 2 3.90 7:40 1.690 0.2279 .0495 18.48 3 5.89 1.868 0.2714 .0393 te ia 4 I 4 5.96 5.04 2.182 0.3389 .0368 16.42 5 6.49 4.61 2.395 0.3793 .0329 15.89 6 7.00 4.00 2.750 0.4393 .0318 15.38 7 70k 3.49 3.162 0.4986 .0309 14.87 8 8.07 2.93 3.754 0.5745 I .0312 14.31 9 8.34 2.66 4.136 0.6166 .0297 14.04 10 8.38 2 62 4.198 0.6230 .0271 14.00 11 8.44 2.56 4.297 0.6331 .0250 13.94 io 8.55 2.45 4.490 0.6522 .0238 13°83 13 8.63 ‘2: VE 4.641 0.6666 1 eee 14 8.84 2416 5.093 0.7070 .0220 13.54 48 10.62 0.38 — — — 11.76 Here a value of maximum loss is assumed ata = ll. The

experiment is not quite comparable with the foregoing, in which the wool is taken from dryness to saturation in 100% humidity ; here the atmosphere is not zero humidity. But there is evidence of approach to the exponential law.

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A set of experimental results from Schloesing’s work on the connection of wool regain and atmospheric humidity is appended for comparison :—

RELATIVE I REGAIN a—x we; too i eS HUMIDITY x is Pe ae I 47 13.0 17.0 1.765 0.2467 . 00228 51 13.6 16.4 1.830 0.2624 . 00223 DD 14.3 1.917 0.2826 .00223 59 15.0 15.0 2.000 0.3010 .00221 64 15.9 14.1 2.2128 0.3280 . 00222 69 16.9 13.1 2.290 . 3598 .00226 74 18.0 12.0 2.500 0.3979 . 00233 80 20.0 10.0 3.000 0.4771 .00259 86 22.5 1 4.000 0.6020 — 93 26.8 3.2 oa — —

The average constant is 0.00225 and the law connecting humidity and regain for this range is :—

] a 1 30 = —log —— = — Serer OB. OF 0.00225 p log The exponential form is :— Regain = Maximum Regain (1—e— 9.00225 Humidity) ,

REGAIN — HUMIDITY = {OO} ° - 60 5 60 + xg 40} oi ee a 20} oe oO oa i i 1 i 4 9 5 iS 290 25 30

io ——> %REGAIN

: ip cr Sige ore

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The mathematical form of the time-regain and humidity- regain laws is similar because they are both expressing the diffusion process, which is the characteristic feature of the phenomenon.

When curves of Regain-Humidity or Regain-Time are plotted, they have, over the ordinary range of atmospheric regain, the same type of equation :— 1. Regain = Max. Regain (1 — e ~*:1°) at humidity “ p.” 2. Regain = Max. Regain (1 —e ~*e‘), at time “ t.”’ or the corresponding logarithmic forms :—

Kee lag E

(a—x) Also the relation between Humidity and Swelling of wool substance follows a similar mathematical law.

DIFFUSION THEORY OF REGAIN.

Now it is evident that sorption of moisture in wool must depend in the first instance on the and it is certain that the initial stage is the formation of a film of water by adsorption. The wool tissue is quickly reactive to external changes of vapour pressure. (See table of Hartshorne’s and Allister Wright’s curves, p. 372-5, daily variations of regain.) From this surface layer the fibre substance will obtain water by DIFFUSION, and this is accompanied through a certain range by a swelling up of the tissue ; there will be a complica- tion due to this cause.

To the first approximation, however, the process will follow the diffusion law, and is analogous—in the converse aspect of drying out—to the well-known case of Velocity of Solution of Solids in Liquids. Such phenomena have been studied by Noyes and Whitney and others, who showed that their results were consistent with the hypothesis of a very thin layer of saturated solution round the solid, the rate of dissolution of which is thus dependent on the rate of diffusion from this layer into the surrounding medium. The mathematical law. _ applicable is :— : K = Slog? wh = 7 ‘log Goa where Q is quantity of salt in a saturated solution, x is amount dissolved in a time “ t.”’ Thus the rate of solution depends on the rate of diffusion of

the salt from the saturated layer, into the adjoining layers. The general law of diffusion involved in this discussion may

be stated thus :— Head of Diffusate

Rate of diffusion = Constant x Thickness of diffusion path.

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If the diffusate is a material substance—in the case of textiles it is water or atmospheric moisture—then the “ head ” is the difference of concentration between two faces of a stratum of the medium in which diffusion is taking place. In the wool case, this amounts to a difference in the external vapour pressure and the vapour pressure of water in the wool.

At any given stage within the ordinary limits of regain, 10-20%, wool shows :—

MOISTURE CONTENT SATURATION or x +a e—Kt = 9, i.e., a(1—e—*) +.a e—Kt ea The general equation being x = a (l—e—**).

The quantity called the Deficit or Swelling Deficit is the difference between the actual concentration in the material and the possible or maximum concentration at saturation. Experi- ments on other colloids, gelatin, sea-weed, starch, etc., show similar relations.

Some indirect confirmation of the application of this logar- ithmic law of diffusion, or alternatively, Exponential Law of Regain, is given by some researches of E. A. Fisher, M.A., on the evaporation of water from various colloids. The rates of evaporation from a wet-saturated piece of, wool fabric were ascertained by determining the losses of water from a piece of such fabric exposed over sulphuric acid of definite concentra- tion; i.e., a medium of known vapour pressure. From the curve of weights lost and times taken, the tangents were obtained graphically and the corresponding rates determined. From these the general graph of Rate of Loss and Moisture Content is drawn. It presents some remarkable peculiarities. 43

EVAPORATION — TIME ; WOOL EAFISHER

o a

a

w—» % WATER CONTENT &

Ste ek we ee HOURS ' Fia. 118.

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The curve is obviously discontinuous, the rate of evaporation is not constant at all stages. Along the section AB the rate of loss is constant down to approximately 31° of water; at the point B the first discontinuity occurs and the rate of loss is then linear, i.e., it is proportional to the water content down

REGAIN RATE °F DRYING; WOOL dw/dt =K,

A

=

dw/dt= K;(w-c¢)

_ EAFISHER BW - 20 BB

Fie. 119.

0 oN

to about 11%. Over this portion, which corresponds to’ the

ordinary range of regain for wool, the law obeyed is :—

dw age ek: if this equation is integrated, we have :— log Kzw = K,t'+ C as the equation of the part (31%-11%) of the original curve, from which the rate curves have been derived.

Assuming two values of this :—

log K,w, ="— K,t, + C and subtracting, log K,w, — log K,w, = K, (ts —t,), that is :— Ww 1 WwW log —* = ee oe K t, or K er If w, is the maximum = a, say, and w, is an actual value a instant t, this becomes K = log = = which is a form of the

Law of Diffusion. It thus appears that the general mathematical laws of gain and loss of moisture in wool are of similar form, being, in fact, the converse modes of the Law of Diffusion, at any rate within ‘the limits given above.

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The processes are not uniform, there being plainly a complex of various causes in operation, in some stages. perhaps simultaneously. The chief factor is the Humidity ; tempera- ture, capillary and adsorptive properties, etc., are others. The present investigation is only a starting point for a large research into a field, hitherto almost unworked.

The DIFFUSION THEORY of moisture regain in wool, outlined here, recognises the existence of an aqueous film on the surface of the fibre giving and losing water as vapour to the atmosphere, according to the relative humidity (vapour pressure) and on the other hand supplying or taking water from the wool substance. Of the physical actions occurring in this complicated system, the diffusion in the internal tissue of the fibre will be the slowest and probably governs the general rate of transformation. There will be a vapour pressure gradient in the superficial water film, another gradient in the tissue of the colloid fibre, and perhaps a third in the saturated air just outside the external film. Mr. E. A. Fisher has suggested that the second bend in his evaporation curves is explainable from this basis. It is obvious that the whole Subject is ripe for investigation.

‘ON THE THICKNESS OF WATER FILMS.

Given certain data for the wool fibre, it is easy to calculate the approximate thickness of layers of water which might be deposited thereon in special circumstances of humidity. Thus, take the case of Botany wool, 80s quality ; from the tables given in the chapter on the Physical Properties of the Wool Fibre, we may assume a diameter averaging 0.002 centimetres, and length 3 inches = 7.62 cms., and the specific gravity of wool substance will be taken as 1.30 that of water. Considering the fibre as a cylinder, this gives for the volume of unit fibre in this quality 0.000,023,939 cubic cms. or nearly 25 millionths of a cubic centimetre. Now the volume of a kilogram of solid wool—that is, irrespective of air spaces—is 769.23 c.c., and therefore the number of fibres per kilogram weight is 32.133 x 10°. The curved surface of a single fibre is equal to its circumference multiplied by the length, i.e., 0.04785 square -cms., and for the whole of the fibres in a kilogram this is 1.5385 < 108 square cms. If now we assume 10% of moisture on the weight of the wool, or 100 grams, and consider this to be a surface film, its thickness would be :—

Volume of water 100 See OL Sen = Area covered 11.5385

‘6.5 x 10—° cms., or 65 millionths of a centimetre ; or about _25 millionths of an inch. 3

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Now take the case of a Southdown, 56s quality. The corresponding, quantities are as follows :—

Average diameter = 0.0028cm. Length, 4ins. = 10.16 cms. Volume of single fibre = 0.000,125,2 c.c. Number of fibres per kilo = 12.296 <r. Curved surface of single fibre = 0.08937 sq. cms. é‘ Total curved surface of 1 kilo = 1.0989 x 10° sq. cms. At 10% moisture, Thickness of film = 8.9322 x 10—° cm., or 89.322.millionths of a centimetre.

It is pointed out in the chapter on Theoretical Principles, earlier in this book, that 1 gram of water could cover 16 x 107 square centimetres and that this thickness would be 0.6 x 10-8 cm. LEdser gives as the probable diameter of a molecule of water taken as a sphere 3.75 x 10-8 cm. Evidently the moisture layers are hundreds and thousands of molecules deep.

HARTSHORNE’S RESEARCHES.

Reference has already been made to the extended experi- ments by W. D. Hartshorne in America. His quantitative results differ in detail from those of Schloesing, made previously, and are not in general more accurate. From his data, Hart- shorne deduced a law which is stated as follows :—

‘*'To summarise these laws of regain for cotton and worsted we can say :— First, the general law for cotton and worsted and probably for any other textile fibre may be represented by the formula :— KRT = H X 5771.44 x 108 in which H represents any given relative humidity expressed decimally. R the regain at any absolute temperature T. K is a variable coefficient in such a way that for H = 1| or saturation the product KRT is a constant quantity represented by the number 5771.44 x 108. In this 5771.44 is the weight in grains of a cubic foot of aqueous vapour at any temperature multiplied by the corresponding absolute temperature in degrees Fahrenheit, divided by the maximum elastic force of aqueous vapour at that temperature expressed in inches of mercury.

Second, for any given temperature the relation of values of R to the variable K for both worsted and cotton is expressed by a hyperbolic equation differing for each substance. Third, for any other temperature the law for worsted is :—For the same humidity the squares.of the regains at different temperatures are to each other inversely as the cubes of the corresponding absolute temperatures. Fourth, the law for cotton is :—For the same humidity the first powers of the regains at different temperatures are to each other inversely as the first powers of the corresponding absolute temperatures.”’

While there is some value in the work of Hartshorne on textiles, it is difficult to see how these “laws” could have been deduced. The quotations are taken from a reprint of his papers in a technical journal.

Page 419

395 SORPTION HYSTERESIS.

The difference in the value taken up under a given stimulus according to the direction in which the material approaches that value, i.e., from the excess or defect side, occurs in sorption as in other phenomena in these colloid bodies. Masson and Richards noted that different values of the regain were obtained. in an atmosphere of given humidity, according to whether the fibre was wet or dry when introduced. Some of their results on cotton are given herewith :— I

RELATIVE GRAMS OF WATER TAKEN UP BY 0.984 GRAMS VAPOUR DRY COTTON. PRESSURE. FROM DRY. FROM WET.. 0.100 0.0175 0.0198 0.294 356 0406 0.500 509 0593 0.710 716 0840 0.952 1606 0.972 1563 1792

Probably a similar phenomenon occurs in wool ; it is a case of hysteresis, i.e., a result varying with the method of approach and arising from the previous history of the material. This is not merely a “time-lag”’ or incomplete attainment of equilibrium, owing to delay. It is a consequence of the colloidal nature of the material and is evident in the elastic properties also. Material dried out at different temperatures to the same standard of moisture is not necessarily in identical states.

RECENT WORK.

The work of Shorter and Hall (“ The Hygroscopic Capacity of Wool in Different Forms and Its Dependence on Atmos- pheric Humidity, etc.’’) gives some interesting data on the general question of moisture and wool, besides yielding probably the most accurate results yet obtained. The outstanding difficulty in all this work is the exact measurement and control of the humidity ; if the experimental conditions in this respect are inaccurate, the time lag in taking up moisture by the wool may lead to great errors. © ©

The following table gives the average regains for ordinary indoor conditions, along with the standard regains for com- parison therewith :—

MATERIAL. STANDARD REGAIN. AVERAGE INDOOR REGAIN. Scoured Wool 16 15.5 Tops, in Oil 19 15.5 * Tops, Dry 18+ 16.0 14 15 Yarns, dry or in oil 184 16.0 dry 15.5 in oil

Cloth 16 15-17

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The following results apply to natural variations in samples fixed on an outside wall :—

REGAIN OF SAMPLES IN OUTSIDE BOX.

1923. MEAN MEAN WORSTED I HOSIERY 80s I 56s MONTH. I TEMPER. I HUMIDITY) CLOTH. WEB. BOTANY. I SYDNEY. Fah. % % % ee eee Ae February 44.15 84.35 24.58 20.04 22. Ta 21.14 March 46.90 73.50 20.20 18.02 19.31 19.39 June 61.60 41.10 14.76 14.09 15.07 15.07 July 68.70 76.80 15.99 14.83 16.33 16.08 August 62.30 82.30 18.03 16.19 1444 17.44 Sept. 58.20 80.80 17.60 16.10 21. 49 439 October 51.64 81.44 19.72 17.45 19.41 19.31 November| 30.85 83.00 22.19 10.21 21.38 21.98 December! 38.95 88.50 25.32 23 2) 23.96 24.63 AVERAGE 52.48 80.87 19.82 17.46 19.15 19.14

Under indoor conditions, a sample of worsted cloth had an average regain of 16.04% under an average humidity of 71.24% with a mean temperature of 59.63°F. As is to be expected from the known variation of humidity with temperature, the outdoor samples have their highest regains in winter and the lowest in summer, while the indoor samples vary in exactly the opposite way. The great differences between greasy and scoured wools, observed by other investigators and well known in practical circles, were noted in this research also. There are large variations in different raw wools, Botany having particularly high hygroscopic capacity ; there is of moisture absorbing power with age. The wool grease exercises an important influence (see Allister Wright, earlier in this chapter), and as is common knowledge, this varies very greatly in the different I wools. While Botany wool showed in one case a difference of 9.62% between greasy and scoured, Crossbred exhibited only 1.55%, Yorkshire Hog wool 3.21% and Cape Wool only 2.50%.

GENERAL REMARKS ON HUMIDITY

The determination of the humidity of the environment is the prime necessity in all experimental work on absorption of moisture, and it is no less essential to ensure that a true equilibrium is obtained between the air and the material. The method of using a Sulphuric Acid solution of known concentration to produce a superincumbent atmosphere of determinate humidity has been a favourite with investigators, probably because of its comparative simplicity. It was employed, with some refinements, by Hartshorne, and also— but only as a check method—by Schloesing. It is necessary in using this mode of working to avoid stagnation of the

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*

air; the layers of air near the sorbing material are not in identical state with the general mass of air in the enclosure. Hartshorne rotated the test samples to ensure this relative circulation. It seems to be assumed that Schloesing was not alive to the phenomenon of “lag” in the wool, etc., taking up the equilibrium humidity. In his 1893 paper, Schloesing states :— ‘‘ Tl faut amener la substance mise en expérience & une humidité 4 peu pres déterminée d’avance. On en constitute, dans ce but, un lot homogéne dont en détermine lhumidité par un dosage. Si la substance est & dessécher plus ou moins, on l’étale dans une étuve & 30° ou 40° jusqu’a ce ait perdu une proportion déterminée de son poids. Si, au contraire, elle doit étre rendue plus humide, on lexpose dans un endroit tel qu’une cave non aérée, jusqu’a ce qu’elle ait pris le poids voulu.”’ Moreover, Schloesing had previously conducted researches - on hygroscopic substances, e.g., tobacco. The first method— and that by which his published results were obtained— consisted in passing humid air through a long narrow tube containing the fibre under investigation, then absorbing the remaining moisture in sulphuric acid drying apparatus, and collecting the air in a gasometer. Thus the humidity of the air and material were determined from exact weighings. It is to be noted that the accuracy of this method is not impaired at the higher temperatures (35°C.). It is obviously difficult to get reliable observations at or near 100% humidity or saturation. A slight fall of temperature is bound to produce condensations not only on the apparatus but on the material under experiment. Consequently the equilibrium values at saturation show great variation. It is almost certain that this superficial deposition of actual liquid takes place. When cloth pieces are bleached in the old- fashioned sulphur stoves, it is found that in foggy weather that as the chambers cool down, the fog is sucked in and the fabrics become covered with the minute carbon particles from the soot of the atmosphere. Now it is well known that these floating particles of the air form the nuclei for the deposition of the atmospheric moisture when the temperature falls to the dew point. If the particles are actually visible on the cloths, it is certain that there has also been a deposition of water droplets on the fabric. It is plain that at this stage of the sorption process the conditions become indeterminate, and it is unlikely that any data are generally applicable. The full treatment of the wool-humidity problem in the present chapter proves that the complexity in the sorption cannot be repre- sented by any single relation or “law ” throughout the whole range of zero to saturation. Table B, from Hartshorne, American Dyestuff Reporter, January 28th, 1924.

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Comparison of Schloesing’s Regain Figures on Combed Port Philip Merino Wool with Hartshorne’s at Same Conditions.

TEMP. REGAINS. CENT. H % SCHLOESING I HARTSHORNE I DIFFERENCE. 12 24.5 8.3 8.38 +0.08 24 25.8 8.3 8.13 acd ORE 35 31.8 8.3 8.79 +0.49 12 57.5 14.9 15.38 +0.48 24 61.8 14.9 15.22 +0.32 35 69.4 14.9 16.12 +.1.22 12 83.1 21.9 22.04 +0.14 24 86.3 21.9 21.88 ie 02 35 89.2 21.9 21.84 —0.06 12 95.4 29.0 27.82 ek TR 24 95.7 29.0 26.27 ne 12 35 96.1 29.0 25.19 8, Bi

The “Setting” Properties of Wool.

There is an intimate connection between the plasticity of ° the wool substance and the application of moisture and heat and many technical processes, particularly in finishing, depend on this. In the previous sections of the subject of wool and moisture only the ordinary range of weather humidities and temperatures has been considered, but wool is exposed in technical operations to moisture in the extreme forms of boiling water and steam even a little beyond boiling-point. Under such conditions the behaviour of the wool substance shows important peculiarities. The process of spinning is one of the earliest stages in which the wool fibre is subjected to stresses, the making of yarn causing both elongation and torsional strains. Doubling and weaving may add to these and produce bending, with the general result on the fabric of ‘“‘ a mass of unbalanced The presence of such strains can be demonstrated by the use of polarised light (Harrison). Under the prevailing tem- perature and humidity, these deformations from the pristine state of the fibre may remain latent, but when the conditions are altered the internal elastic forces are no longer controlled and their consequences may then be developed. As an example, consider a hard-spun tightly-set weave in crossbred serge of low quality. Such a fabric taken from. the loom and placed in the moderately warm liquor of a scouring machine becomes crimped and cockled all over its surface in the endeavour of its elements to relieve the many distortions of their earlier treatments. No finishing routine is possible on such goods which does not recognise and deal with this special condition. It is now apparent that the phenomenon here

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discussed is concerned in the various wet operations of finishing I and dyeing, the processes using steam and hot air, and those also involving applications of moisture. Thus the following will be included :—Crabbing and greasy blowing, scouring and milling, boiling, dyeing, tentering, blowing, pressing, dewing, steaming and shrinking ; and stretching and conditioning of arns. 4 Broadly speaking, the following principles govern the behaviour of the wool fibre under these circumstances :— 1. If, while in the dry or comparatively dry state (i.e., non- plastic), wool is deformed—that is, there is imposed some strain—it will tend to recover its original con- formation when its humidity is increased. This may occur by exposure to a moister atmosphere, by wetting, or even by simple heating. 2. Wool loses its rigidity almost completely, that is it becomes plastic, in boiling water, or even at lower temperatures for extended periods. 3. Owing to the viscous or plastic property, the physical behaviour of wool under all agents is greatly influenced by the factor of time. (See Physics of Wool Fibre for ‘* creep, lag,’’ etc.). I Owing to the imperfect realisation of these properties of the fibre substance, misunderstandings and even controversies have arisen as to the true behaviour of wool under certain conditions. One of these is the dispute as to whether a wool fibre shortens or lengthens on wetting-out. This entirely depends on its previous history. Ordinary hair, free from grease, increases its length when moistened, but the effect in unstrained wool fibre is very slight, though there is considerable increase in diameter on wetting-out. <A fibre which has been well stretched while wet and dried without heat tends to shorten on being released. If the wet stretching had been carried out at a high temperature it would have retained its stretched length. This could well be described as PLASTIC SETTING; for obvious reasons it is sometimes termed Permanent Setting. Where the higher temperatures are not employed, as in London Shrinking, the result sought is—not the impress of a given conformation on the material as in plastic setting—but only the release of strains ; such an effect, however, is of a lasting character and is a “ permanent set,” though not of the. type considered above. Fibres under these two treatments would be finally in different physical states, notably as regards their susceptibility to moisture. The plastic setting is a fixation in a new conformation, though it may have involved release of previous strains. Plastic setting is employed in crabbing and greasy blowing, boiling or potting, partially in tentering, in ordinary and

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pressure blowing, and in pressing. The processes of shrinking, steaming and conditioning and the results of humidification involve effects of the second kind. These various operations will receive detailed consideration under their respective headings. A fibre which absorbs moisture suffers a decrease in tensile strength which would be expected ; a wet jelly is mechanically weaker than adry one. A Strength-Humidity test by Barwick gave the following results :— oO

6 LBS. % LBS. % LBS. % LBS. 44 186 57 173 72 168 44 182 59 174 68 173 75 168 47 181 60 175 70 159 77 165 56 180 62 175 71 173 88 167 56 175 65 169 72 169 88 160

There is a great increase in the extension or elongation produced by a stress in the wetted as compared with the dry fibre, and this applies also to the extension at break. The difference between the wet and dry fibres is largely a question of the relative importance of the viscous and elastic properties of the wool substance or alternatively of the plasticity and rigidity. It is possible to produce permanent effects in wool substance by chemical agents, e.g., Chlorine, Formaldehyde, strong Caustic Soda solutions, etc. Some interesting experiments made by the Wool Research Board on the stretching of yarns, while in a wetted or turge- scent state, have recently been published. Ordinary yarn in normal condition may elongate, say, 10-15% before breaking ; the same yarn thoroughly wetted and the fibre swollen shows extensions of 30%, or even 50% before rupture. There is a corresponding diminution in diameter. If the wetted yarn is subjected, while elongated, to a plastic setting—or alternatively to a chemical fixation—it behaves in the normal manner and is permanently extended ; its diameter is similarly permanently reduced. Thus a yarn of finer “ counts ”’ has been evolved by this treatment. Reference to the section on the Physical Properties of Wool will show that what has occurred in this routine is an actual elongation of individual fibres, and not a “slip” of the yarn components. Obviously the twist per inch is lessened. It is said that permanent elongations of 20% are quite practicable.

The “ Conditioning” Process.

In practice the different methods of artificially altering the moisture content of wool materials invariably consist in the addition of water in the form of liquid or vapour to the wool moisture. This is carried out for two reasons :— 1. To bring materials to the commercial standards of regain ; or to obtain undue weighting by supplementing the natural moisture.

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2. To improve the textile qualities by eliminating strains, _ reducing the tendency to “ i.e., irregular twisting, improving handle, etc.

Conditioning may be applied to wool in the form of tops, yarns and fabrics. The most perfect method of restoring the natural moisture to all kinds of wool material is to use the humidity of the air as the vehicle or medium. This raises the question of the best circumstances under which the absorption of moisture may be carried out ; the factors capable of control being humidity and temperature. The general problem has been discussed on its theoretical side in the preceding sections of this chapter, and it is now necessary to make the practical applications. If the object is to secure the utmost regain possible in the material, it can be carried out in different ways, depending on the time available. At 5°C. or 41°F., the atmosphere even at saturation only holds 6.8 grams of water per cubic metre ; that is, this comparatively small amount of water corresponds at that low temperature to 100% relative humidity. Hence wool tops, yarns or cloth pieces exposed under these circumstances to acquire several per cents. of regain will need considerable time. On the other hand, the air on a warm summer’s day at 30°C. or 86°F. holds 30 grams per cubic metre at saturation or 100% relative humidity. The same materials in this environment can’ plainly obtain the desired moisture in a shorter period. In the taking-up of the moisture by the wool tissue it obviously requires an enormously greater renewal or interchange of the humid air at the lower than at the higher temperatures. What then is the basis of the strong impression among practical men that the best results are obtained, when time permits, at the lower temperatures ? In the first place, as may be seen by in- spection of the humidity tables, a slightly higher final regain is possible at the lower temperature. Secondly, the danger of mildew, etc., is less. Thirdly, if two cloths with the same regains but at different temperatures are taken, the colder would, by the test of handle, be preferred. Another mode of presenting the principle involved above is seen in the following table, due to Hartshorne, in which wool is assumed to be maintained at a condition of 20% at various temperatures :—

TEMPERATURE, PER CU. FT.| GRAINS CU. FT. RELATIVE FOR SATURATION. |FOR WOOL AT 20% HUMIDITY. oO 98 19.0 16.7 as” 80 11.0 9.0 82 60 5.8 4.5 77.5 40 2.9 2.1 73.0

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404 CELLARING.

The usual practice when adding artificial moisture to wool is to reserve a special room, often in a basement—situations near the mill dam seem to be preferred—and produce humid surroundings by devices such as the following :—

1. Place the cops, spools, etc., in a room with wetted floors for ten days or a fortnight. 2. Drive a blast of steam through until it produces an artificial fog. 3. Place the bobbins between wet cloths or blankets for 24 hours, or overnight. 4. Place the spools in special trays aad play a very fine spray over them.

But other and cruder methods have been employed, such as totally immersing a skep full of cops under water or steaming the skep with cops in a small room or “ conditioning oven.” Conditioning machines run the threads over rollers which are partially immersed in a trough of water or conditioning liquor ; by varying the depth of immersion and speed of these rollers, the thickness of the film of water taken up may be roughly controlled. Other machines spray the yarn in bobbins, spools or tubes while they are carried on a travelling lattice. Tops may be similarly conditioned.

It is not unusual to make sundry additions to the trough water, to secure rapid and thorough penetration ; soap, and more rarely sulphonated oil (Turkey Red oil), are used. The latter is a dangerous though effective agent. Very little consideration is needed to show that, above all, the conditioning of yarn should be as uniform as possible, i.e., there should be ‘the same weight of water per yard. It does not seem possible I that many of the schemes cited above can secure even an approximation to evenness. On the bobbin the thread which gets the least conditioning—that nearest the barrel—is followed by that which gets the most conditioning, the outside layer -of the next bobbin. Thus, the foundations of a series of barry pieces are laid. If in these cruder methods anything is added to the water, it cannot be evenly diffused through the layers -of yarn, but must be preferentially absorbed in the outer layers. Final defects in cloths due to such causes are met ‘with in consulting practice. Conditioning lessens the tendency of yarn to snarling, but it is a frequent source of controversy, as many of its defects are not revealed until subsequently, even as far as the finishing stages. It is certainly a potent cause of mildew and bacterial decay in the fabric. The steaming of finished cloths to remove press or blowing lustre is indirectly a conditioning process, and so-called ** dewing ”’ or loading machines directly so. In the latter, the

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cloth is exposed to a fine spray produced by a brush revolving in a trough of water, or a series of fine jets. On a large scale such machines can deal with 2000-5000 yards per day and give 5-7% of the moisture to the fabric. Serges, meltons, gabardines, and suitings show increases of from Over conditioned cloths have been the occasion of very serious damages in the package for export on long voyages. The autographic tests described in the section on the Physical Properties of Wool make it clear that there is a slow elastic recovery in wool, in which strains are wiped out and the original conformation regained. This action occurs in those methods of conditioning which involve much time, e.g., cellaring and this apart from the gain of humidity which goes on at the same time. Wool as tops appears to come from the machinery with about 10% of moisture even from the circles of combs which are maintained at temperatures a little above boiling point. They will tend to “set ’’—i.e. release latent

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strain and condition—for several weeks; crossbred yarns particularly need “seasoning ’’ before weaving. Yarn with much less than normal regain gives trouble in the weaving. It must be noted that yarn which has been conditioned is already partly swollen and yarn is therefore spun about two counts finer to allow for this. The practical man styles the process of releasing strain during conditioning of yarn as “ bedding ”’ of the fibres in the yarn. It follows that if this stage takes place in the piece after weaving the tendency will be to give fullness to the fabric.

Ventilation and Humidification of Works.

This subject of very great practical importance naturally falls into line in its textile applications. with the general discussion of humidity. On the side of humidification the textile industries demand a properly regulated atmosphere for the production of yarns, and apart from the needs of the

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operatives there are special problems of ventilation in dye- houses, scouring and bleaching sheds, shrinking, tentering and blowing rooms, and the like. It will be convenient to consider the ventilation aspect first, and it is instructive to summarise the various sources which contribute moisture in excess or create a deficit in textile work. In general, the excess of moisture in the atmosphere of a textile works arise from the processes, the products, and to some extent from the operatives. All the wet processes contribute humidity to the atmosphere of the workrooms, e.g., scouring, conditioning, bleaching, boiling, dyeing, tenter- ing, crabbing and blowing, shrinking, etc. Wet products, as wool, yarns, cloth, pieces in intermediate stages or passing through particular operations yield enormous quantities of water to the air. It is stated that a square foot of the surface of a boiling dyevat will give off to the air approximately a pound of water per hour. Assuming the standard temperature of 60°F ., the humidity table shows that for 100° humidity a cubic foot of air then contains 5.8 grains ; therefore 7000/5.8 or practically 1200 cubic feet of air will be saturated at 60°F. by a square foot of boiling dyevat surface every hour. Now the area of an eight-foot diameter circular vat will be slightly over fifty square feet. As a rough estimate, we may therefore say that a thousand cubic feet or a space 10 x 10 x 10 feet is saturated every minute by a boiling dyevat such as here considered. As soon as the general temperature falls con- densation commences with the formation of fog and copious precipitation on adjacent surfaces. In fact, whether the temperature falls or rises to any practical limits, this con- tinuous development of vapour is bound to over-saturate the air and produce the effects described. It is therefore not in the least remarkable that many dyehouses are run practically in a continuous fog, that the roof structure is rusted in the ironwork and rotten in the wooden portions, and that drips and condensations are present on every exposed surface ; the final result being an unending crop of dyer’s “stains and Exactly the same conditions occur in some power laundries. The question of ventilation and humidification of workshops is complicated by the heating conditions, and these include not only special heating apparatus such as radiators or lines of steam pipe or hot-water piping, but the running machinery. It is not usuaily perceived that the energy of motion put into the running plant is finally dissipated in one way or another as heat. One horsepower is a rate of working of 33,000 foot pounds per minute, and a British Thermal unit is the equivalent in mechanical work of 776 foot pounds ; hence a horsepower dissipates about 42.5 B.T. units per minute.

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A third factor is the presence of the operatives themselves. In a large weaving shed where each loom may have one attendant, or in mending, etc., rooms, this is appreciable. The bodily heat per operative is estimated at 300-900 B.T. units per hour, say 500 average. In normal breathing, a person takes 15 breaths per minute, or 2.3 x 104 per day, and the total weight of water breathed out per day is about 10 ounces. Or, the average human being gives off about 63 grams of water per hour in repose and considerably more while exercising. Now at 0°C. the quantity which saturates one cubic metre of air is only 4.84 grams. The first figure neglects the considerable amount exhaled in the perspiration. The official standard of ventilation recommended per person per hour is 3000 cubic feet, which means an average interchange of six removals per hour in ordinary rooms, where an air space of 500 cu. ft. per worker may be assumed. In a case like the finishing side of a laundry using many gas-heated appliances, some modification of this would be required ; the carbon monoxide from imperfectly burnt gas is a most dangerous blood poison. A room 60 x 50 x 10 or 30,000 cu. ft. capacity could be satisfactorily ventilated by a 20-25 inch fan taking approximately one horsepower, used as an exhaust.

SYSTEMS OF VENTILATION.

The ways in which the flux of heat occurs may be con- veniently summarised in the following table :—

INFLUX. EFFLUX. 1. Mechanical power dissi- I 1. By convection in venti- pated as heat. lating air. 2. Heat directly supplied by I 2. Conduction in walls, etc., radiators, etc. of the building; and 3. Body heat of staff. roofs. 4. Solar heat by radiation. 3. As latent heat in humidi- 5. Special sources, from fying water. plant, near boilers, etc.

There are two leading principles on which systems of ventila- tion and humidification in factories are based. In the one, exhaust fans, chimneys, upcast shafts, louvres, etc., are employed, the air and steam being withdrawn from the interior and delivered to the atmosphere ; the reduced pressures thus produced within the enclosure—i.e., partial vacua—cause replacement from the outer air by any channels, windows, doors, etc., which may be available. This is the VACUUM system. It has been in the past the prevailing method, and in general has been grossly inefficient.

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_ The second method supplies air from the exterior, usually by forced draught or fans—with or without treatment for dust removal, humidity, and temperature—and distributes this fresh, cleaned, treated air by proper ducts or channels through- out the enclosure. There is obviously produced in this case a slight excess of pressure in the interior space, and this causes a general displacement of the inside air through proper channels, windows, special ventilators, etc., to the external atmosphere. This is the PLENUM system. It is perhaps unnecessary to say that it offers elements of control completely absent in the older methods. It is impossible to meet the complex circumstances of humidity, temperature, cleanliness, with sufficient volume for freshness, needed in some textile operations (such as spinning fine worsted yarns for white fabrics) by the so-called natural methods. A complete plant capable of fulfilling all the conditions must include :— Fans of sufficient capacity. Heating appliances, e.g., coils, radiator sections, etc. Filtering appliances to remove dust. Wetting plant or steam supply; to eee the required humidity. 5. Distributing conduits. It is instructive to consider in the first instance the simpler problem of clearing a dyehouse, scouring shed, or bleach-house of excessive steam. In this case it is not always necessary to heat up the air, or only to a small extent. The temperature must not be raised too much, as hard manual labour is best performed at or below 60°F. No satisfactory ventilation of a dyehouse can be obtained by exhaust fans alone; if the working was adequate in summer it could not be completely so in the cold and foggy days of winter. Hoods are commonly fitted over the dyeing machines or vats, but they are a disputable innovation occupying much of the air space, obstructing light and vision, and collecting dust and moisture on their surfaces. Cases have been successfully dealt with by a simple plenum installation with good distribution, no provision of hoods being made ; sometimes a number of stand flues from the floor—similar to the well-known Tobin tubes— have proved useful. Ducts may be constructed of tin plate or thin match boarding. There is a very wide-spread fallacy regarding the relative weights of: dry and humid air, which requires thorough correction. Consider an enclosed space containing a given volume of dry air. If into this air a quantity of water is evaporated, then the air plus water vapour occupying the same volume will undoubtedly weigh more per cubic foot than the original dry air. The mercury column of a barometer

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placed within this room would rise. Both these are artificial conditions which do not arise in practice. In the ordinary case, when additional water vapour is passed into an enclosed space, e.g., a room, an excess of pressure is produced and a displacement occurs, part of the medium flowing away till the normal pressure is regained. There is thus left a mixture of air and water vapour, as against the original dry air. Now this mixture is less dense, or weighs less per cubic foot than dry air, and would rise through drier air. Water vapour is roughly three-fifths the weight of a corresponding volume of dry air. Hence if the water can be maintained in a volume of air as vapour it may be ventilated away by upward displace- ment. A common fog, i.e., a suspension of water particles in air is necessarily heavier per cubic foot, and tends to seek the lower levels. Saturated air at 52°F. is 99% of the weight of the same volume of dry air; at 202°F. it is only 69%. Bearing these considerations in mind, it will be seen that the supply of fresh air must be in the first place warmer than the damp steam-laden air of the interior; the important point is the greatly enhanced capacity for carrying moisture of air at the higher temperatures. Thus, if air at 52° is heated to 72° its capacity for moisture is doubled and it is four times what it was at 32°F. But a practical limit is set to this by the necessity of keeping the temperature of the workrooms low enough to prevent enervation of the operatives; there is a distinct falling off in the efficiency of the staff in over-heated rooms, though this may be due to lack of freshness rather than relatively high temperature. When the proper quantity of air at the required temperature is ensured, it may be dis- tributed partly near the roof and partly at a height a little above head level ; at special points where extra evaporation is taking place, particular provision by a stand tube, etc., may be made, the outlets for the moisture-laden air may be by roof ventilators of a chimney type, louvres, swing windows, or other devices, but all these must be controllable to prevent draughts. It may be necessary to instal exhaust fans in addition, but it is plain that every case requires special investigation, as the circumstances are all different in respect of dimensions, lay-out of plant, nature of construction, aspect, existing provision, etc. It is not always necessary, contrary to prevailing ideas on this matter, to place exhaust fans at the highest point available ; they may be put at lower points to secure a circulation of fresh air near the workers. Where the difference of pressure on the two sides of the fan is not great and the flow resistance is small, the propeller type of fan is suitable. In situations where corrosive vapours are en- countered, copper blades have been employed ; it appears to be a case where aluminium would have special merits.

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In the spinning of fine yarns it is essential to maintain a proper humidity of the air to secure smoothness and evenness of the thread. Electrification troubles are increased by dryness, an east wind and dry frosty weather are worst in this respect. On the worsted side, a temperature of 70—75°F., with a humidity of 65-75°,—the higher figures in the preparing rooms—appear to be agreed practice. In “* Bradford ”’ spinning, a lower humidity of 55% is recommended. The French system of spinning without oil requires much higher working, 80°F. and 80° humidity. As these varied circum- stances cannot be met without artificial control, diverse arrangements of mechanical sprays, steam jets, wetting of floors, etc., are used. There are official restrictions on the degree of humidity permissible at certain temperatures in spinning rooms and tests are periodically taken by the wet and dry bulb thermometers for purposes of verification. As it is also worth while in securing humidity to obtain clean or dustless air and a proper temperature, it is patent that a plenum system is best adapted to this end.

The moistening of the air is carried out by blowing it through fine sprays, over wetted surfaces such as matting, or by steam jets. The dirt is strained out by screens of canvas, etc., which may be kept wetted by perforated pipes from a water supply. — The entire arrangements are controlled by thermometers for temperature and by some form of hygrometer—either the hair type or wet and dry bulb thermometers—for the humidity. Experiments and working on the large scale show that humidity of nearly 100% can be given to the incoming air by these means and not less than 50-60°, maintained in the sheds; but if higher humidification in the workrooms is required then steam jets or atomised water must be used. The latter enables some cooling to be effected. More elaborate arrangements for cooling the inflow of air may be made in special cases, e.g., if a borehole with a plentiful supply of cold water is available ; a circulation of this through a battery of pipes round which the air passes forms a good means of securing a reduction of temperature.

In an ideal system of drying, the temperature at the end of the operation would be atmospheric ; an absolute dryness, far from being required industrially, is to be avoided. The historical method of putting pieces out in the fields all night, however impossible in these modern days, had at any rate the merit of being a natural system. It is perhaps probable that, in the demand for output, the importance of bringing cloth to a proper “ condition ”’ is not so well recognised, and it is also likely that the best methods of piece conditioning have not

been worked out. The superiority of the older processes,

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‘“degging ” or cellaring, which required much time, because the absorption took place from the vapour state as against the application of liquid, is unquestioned : there are objections e.g., spotting, etc., to the liquid processes.

The following hypothetical example gives an instructive illustration of the questions of regain, humidity, etc.

There is a kind of analogy between the diffusion of water vapour in the atmosphere and the solution of a substance in liquid. Thus, suppose that the familiar cane sugar is dissolved in water ; then at various temperatures we obtain :—

Temperature .. OQOCent. 5 10 oS, 20 25 Solubility in 100 : parts water .. 179.2 184.7 190.5 197 203.9 211.4 gms

If from any given temperature in the table above, the solution is cooled, some of the dissolved sugar will come out in the solid form. On the contrary, if the temperature is raised, then a further quantity of sugar could be taken into solution, or, in other words, the solution would no longer remain saturated.

Now consider the case of water vapour in the atmosphere. The short table below gives a series of temperatures and weights of aqueous vapour corresponding thereto, in grains per cubic foot :—

Temperature.. 40 Fahr.50 60 70 80 90 100 Water Vapour 2.86 4.10 5.8 8.07 11.03 14.92 20

Following out the analogy, if from any given temperature the atmosphere is cooled, some of the aqueous vapour will come out as liquid water ; on the contrary, if the air is heated, then a further quantity of moisture could be taken up, in other words, it would not be saturated and its relative humidity would be less than 100%.

Let us now apply these considerations to the case of a wool shed having dimensions of 100 x 50 x 20 = 100,000 cubic feet. The volume of air in this shed, supposed at 40°Fah., would carry for saturation 100,000/7,000 x 2.86 = 41 lbs. of water. If its temperature were to be raised to, say, 60°F., the relative humidity would be :—

Actual moisture present 2.86 x 100

= eee Boe i ae O nee ~ Maximum moisture possible —5.. 80 ane 7

If the wool shed be supposed to hold 2,500 average wool bales of 300 Ibs. weight, there will be a total weight of 750,000 lbs. Now an ordinary bale of wool has an approximate volume of 20 cubic feet, and therefore the apparent density of wool in the bale is 300/20 or about 15 lbs. per cubic foot,

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i.e., wool in the bale has an apparent density about } that of water (624 lbs. per cu. ft.). As the actual density of wool substance is 1.30, it follows that 20 cubic feet of wool weigh 1.30 x 624 x 20 = 1,625 lbs., and this gives a figure for wool of 83 lbs. per cubic foot. Hence, 300 lbs. of solid wool substance would occupy 300/83 = 4 cubic feet approximately. Let us assume a normal regain of 169%; then the amount of water in the 2,500 bales is 750,000/100 x 16 = 120,000 lbs. The average English conditions may be taken as 16% regain, 60°F. and a relative humidity of 70%. We will now assume two cases for purposes of illustration. A relative humidity of 70% at 60°F. corresponds to saturation at about 49°F. During this assumed fall of temperature the relative humidity of the air rises, reaching finally 100% and the regain of the wool follows with some lag, the amount of which is indeterminate and dependent on the circumstances. At 49°F. the air is saturated and the regain would be approxi- mately 27 (Cf. tables of regain, humidity and temperature). The new total weight of water is 750,000 x 27/100 = 202,500 Ibs., and the required increase in moisture is 82,500 lbs. This is to be supplied from the air by diffusion through the wool, and will obviously necessitate very many renewals of the air of the shed, which we have seen carries only 41 lbs. of water at 40°F. Taking a second case, a relative humidity of 70% at 60°F. corresponds to only 37% at 80°F., for reference to the short. table of moisture content and temperature gives 70/100 x 5.8 = 4.06 and 4.06/11.03 x 100 = 37%. During this rise of temperature the relative humidity falls, the wool parts with moisture to the atmosphere, i.e., the regain diminishes to a value of about 12.7%. Therefore the. total weight of water is now 750,000/100 x 12.7 = 95,250 lbs. and there is a loss as compared with 60°F. of nearly 25,000 lbs. These calculations, while instructive, cannot be taken as. exactly representing the actual facts of the case. The processes of diffusion into and out of a mass of wool in bale form are undoubtedly very slow, apart from the diffusion into the fibre substance. As an indication of this, it has been found that in the case of even severe fires in woollen mills, very often the outer portions only of the bales were injured, the inner mass being almost normal wool and quite capable of manufacture.

HYGROSCOPIC CAPACITY OF WOOL.

Relative Humidity 43.3 I 55.4 I 62.3 I 74.6 I 81.5 I 86.2 I 90.0 Mean Regain of Cloths| 13.12 I 15.62 I 16.72 I 10.01 I 19.02 I 20.93 I 22.47 Schloesing 12.50 I 14.20 I 15.0 I 17.50 I 19.40 I 21.50 I 24.0 Hartshorne 11.60 I 14.00 I 15.50 I 18.50 I 20.10 I 22.10 I 23.60

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The following table gives the content of aqueous vapour in the atmosphere at various temperatures, in lbs. per thousand cubic feet. 7

TEMPERATURE WEIGHT OF TEMPERATURE WEIGHT OF OF AIR. WATER. OF ATR. WATER. O°F. 0.081 70°F. 1.148 10 0.125 80 1.382 20 0.189 90 oak 30 0.273 100 . 2.851 40 0.410 110 3.766 50 0.587 120 4.924 60 0.828 - lbs. ae

The following results from experiments by 8S. Brierley, in 1920, illustrate the marked effect of moisture on the strength of a cloth. In this case, the material was made from a cotton

warp and woollen weft, and the tests were made weft way. WEIGHT AND

AVERAGE AVERAGE STRENGTH. STRETCH. Dry ; 34.2 206.3 2.2 5°% moisture ; 36 153.3 2.6 10% moisture ; 38 138.3 2.9 15% moisture 126.7 3.2 moisture ; 42.8 105 3.4 25° moisture ; 45.6 112.3 3.5 30% moisture ; 48.9 105 3.75 35%, moisture ; 52.6 105 4.4 40% moisture ; 57 111 4.5

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THE DRYING PROCESSES.

Page 441

CHAPTER XI.

The Drying Processes.

A considerable amount of discussion has been devoted to the question of wool and water in the chapter on humidity, but in this section it is intended to treat the particular methods of freeing material from excess moisture, and it will be con- venient to take together all systems, whether based on mechanical means or by the application of heat, etc. In many aspects, e.g., the efficiency of the various methods, it is another of the unstudied branches of the textile art. It will be useful at the outset to make a classification of the methods of drying textile materials into :—

a MECHANICAL; as the use of the mangle and the centrifuge.

II. HEATING; either by actual contact, as in cylinder dryers, or indirectly by currents of hot air, as in stove drying, tentering, etc. There are three funda- mental methods of transferring heat :—Conduction, Convection, and Radiation. Of these, the textile drying processes involve almost wholly the convective principle. III. VACUUM methods ; comparatively undeveloped.

An alternative mode of summarising the textile drying methods is on a basis of differences in materials :—

1. Loose fibre. 2. Sliver. 3. Yarns, as cheeses, cops, warps, etc. 4. Fabrics, usually as pieces. 5. Garments, as in the hosiery and laundry trades.

It will be convenient to study first the removal of moisture by mechanical means, as these are employed to a certain extent on all classes of textile materials. The simplest and most direct is the ordinary WRINGER, MANGLE, or SQUEEZER, sometimes even loosely called a press. This consists of a pair of rollers—wood, brass, iron, ete.—driven

DD

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418

by cogged wheels ; there may be two pairs of rollers forming the DOUBLE MANGLE, and in this case, a guide trough is

*

Fig. 123.—SINGLE WRINGER. (JAS. BAILEY, SLAITHWAITE.)

fitted to give the material a partial turn and contribute to a more thorough squeeze. The mangle is simple, robust and lends itself to continuous feeding ; but it is rough, liable to

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damage fine materials such as hard spun and set cloths of the worsted class. It is further a not very efficient drier in its single form. It is usual to wrap the rollers with cotton or long-wool yarns, or better coverings of rubber ; in the wringing of bleached or chemically treated goods, rubber-covered rolls are essential. The mangle or squeezer has always been the standard apparatus for mechanical drying in the cotton industry, and it has been found feasible to use it in the lower branches on the wool side. Its speed is about 100 revolutions per minute.

The Hydro-Extractor or Centrifuge.

In this device a perforated drum or basket of copper or steel is rapidly rotated round a central vertical spindle, the motive power being steam engine direct, belt, electric, friction drive, or even water turbine. Very many designs exist adapted to various industries, but the usual textile machine is a 60—72 inch cage, surrounded by an external casing of cast iron or preferably steel; this may be flashed internally with lead against corrosion. During rotation, the centrifugal force developed is resisted by the internal surface of the drum, and there is thus set up a pressure in the material; the excess liquid is thus squeezed out and, flying to the outer layers, escapes through the perforations and is drained away. The radial acceleration of a body moving at uniform speed ‘“‘ v ”’ feet per second in a circular path is given by f = v?/r, where is the radius. If, as is generally more convenient, it is desired to express the ratio of this to the ordinary gravitational acceleration (g = 32 f.s.s.), then f/g = v?/rg, or in terms of the number of revolutions per minute, f/g = N?r/90,000.

The following table gives the comparative figures of diameter, speed of rotation, and “ gravity factor f/g ’’ for different sizes of centrifuge :—

DIAMETER OF CAGE. |REVOLUTIONS PER MINUTE.| GRAVITY FACTOR. 2 ins. 40,000 45,300 36 1000 512 60 750 479 72 650 432 84 500 300

When a hydro-extractor is applied to the removal from a mass of fibrous material of the excess liquid its efficacy must depend upon a number of factors :—

1. Centrifugal Acceleration, which may ie made very high in machines of very small diameter.

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2. Liquid resistance to movement due to viscosity and surface tension and actual frictional resistance in the capillary channels ; if these are very small, it will be impossible to remove the contained liquor by ordinary centrifugal force.

3. The wetting of the solid surface of the fibrous material by the liquid. It will be instructive to reconsider the statements in the chapter on Humidity regarding the modes in which a textile material holds water. It is obvious that centrifuging—at any rate of the ordinary kind—removes only the superficial and capillary water of the coarser sort; but it is asserted that severe centrifuging—as in the special smaller machines of the table above—removes some of the water of the gel. The degree of perfection to which water is removed in ordinary practice may be judged from the following example :—

Drying of a Worsted Serge Piece.

Length of piece 63 yards. Weight cuttled from scour. = 102 lbs. Weight of greasy piece with water of condition = 44 lbs. Scouring water, loosely held st ~ GO: Es: Weight after centrifuging aes Ae Water still retained, i.e., beyond water of regain = 13 Ibs. Water removed by Hydro = 465 lbs.

confirming the common works’ view that the dripping piece is roughly twice the grey weight. But compare E. A. Fisher’s and Woodmansey’s experiments cited elsewhere.

Messrs. Coward and Spencer have carried out some accurate experiments on cotton by the aid of a centrifuge of laboratory size, with the object of determining the mode of action and the efficiency of removal of the contained water. It was found, as is commonly observed, that a great part of the water is removed in the first minute of centrifuging, and that the last fractions are very slowly displaced.

Time of run 0.25 0.5 1.0 2.5 5.07.5 10.0 15.0 25.0 Water retained by 100 A 66°9 63.6 59.1 55.153 51.7 50.5 49.5 47.6 units of weight ofcotton B65 61 57 55 53 — 50 47° —

It is obvious that long spinning is inefficient. This slow loss at later stages may be due to the very tardy thinning of the superficial films of liquid on the fibres or to slow squeezing out from within the fibre substance, i.e., from within the gel. Further experiments showed that alcohol and xylene are removed to a greater extent than water, and it therefore follows that this remaining water is not merely enmeshed

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between the fibres, but is within the fibre substance. (Note.— In wool, as the ordinary work of microscopy shows, alcohol produces swelling of the fibre). It is evidently water of swelling, a result confirmed by showing that glass wool similarly wetted—a substance impermeable to water—released a much greater proportion than the cotton. Again, cotton swells noticeably in water, but not in alcohol or xylene.

The following table shows how the efficiency in removal of water depends on the speed of extraction :—

SPEED OF CENTRIFUGAL WATER CENTRIFUGING. ACCELERATION. RETAINED. Revns. per min. f/g=N?r/90,000. Cloth= 100. 7800 I 2770 53 7350 2460 55 7000 2230 55 6900 2170 57 6650 2010 58 5550 1400 65 5400 1300 66

The experiment concluded that “‘ when well scoured cotton was immersed in water the absorption as determined by the centrifuge reached a constant value at the end of five minutes immersion, if the mass were well shaken.”’

In practice, the hydro-extractor will reduce the water content of wool materials to about 60-50% on the weight of the goods. Of this about 30% is water of constitution and imbibition water not removable by mechanical means. The works centrifuge is certainly more efficacious than the single wringer and probably a little better than a double wringer, and it is far less liable to damage the goods. Its greatest defect, from the practical standpoint, is that it is a dis- continuous machine; the actual drying is an intermittent process, occupying—when loading, running down from speed and unloading are taken into account—perhaps less than 20°, of working time. It may not be out of place to note that there are two ways of running machines of this intermittent kind :— 1. Run up to top speed, cut off the power and at once apply the brakes. This is the system of Least Time, but maximum power and also wear and tear.

2. Run up to speed, cut off the power and allow to run down by friction. This is the method of Minimum Power, but longest time ; also least wear and tear. A centrifuge does not dry all parts of its charge evenly ; the inner upper portions are driest, the lowest the wettest, and the material lying next the walls of the cage wetter than the inside portions.

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CAPACITIES OF HYDRO-EXTRACTORS.

It may be assumed that the machine can be charged 4-6 times per hour, and the following table shows the pounds of dry weight of material per charge in the different sizes :—

30 46 60 63-72 INS. Blankets — 100 180 250 Cotton Waste 60 100 160 230 Hosiery 100 150 aa 300 Piece Goods 40-70 100-180 170-300 230-400 Wool, Botany 40 100 180 250 Wool, crossbred 65 160 260 330 Yarn 50-120 80-220 160-400 230-560

POWER DEMANDS.

Some tests on electric drive d.c. machines showed the appended results :—

SIZE. REVNS./MIN. RUNNING H/P. 36 1000 3 48 900 4 60 750 6 72 650 8

But the starting period will require 2-24 times this power.

COMPARISONS OF MECHANICAL DRYING (Rouget).

WwooL COTTON

FLANNEL. CALICO. — en After hand wringing ei, 1.0 0.95 0.75 After heavy pressing, i.e., mangling £0 0.6 0.5 0.4 Hydro Extractor 0.6 0.35 0.3 0.25

The table gives the weight of water in woven fabrics of the fibres named, the dry weight being reckoned as 1.0. It may be noted that wool is easily the most absorptive. A variation of the centrifugal principle has been made in a machine in which the cloth in piece-form is wound into a roll upon a strong shaft, placed horizontally, and this is then spun at high speeds inside a casing. The water is thrown off as a spray into the case and drains away. It is plain that this type, which loses the pressure effect in the ordinary machine cannot be as efficient in action. There is also the danger of the roll flying loose in the chamber.

**VACUUM ”’ DRYING MACHINE.

In this machine, of German origin, the wet cloth passes at full width over a trough in the lid of which there is a long narrow slot. An air-pump produces a partial vacuum in the trough and the rush of air through the fabric and slot carries

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mechanically much of the loosely held water. There may be some vapourising action, but it must be, at the temperature, moderate vacuum, and speed of the cloth of minor importance. The real action is that of blowing loose water out of the meshes

Fie. 125.—HYDRO-EXHAUSTER. (Wm. WHITELEY & Sons, Lrp., Lockwoop, HUDDERSFIELD. ) For extracting water from fabrics in the full width, thereby obviating creases.

of the cloth. True vacuum drying is based upon the principle that the boiling-point of water is lowered by reduced pressure. The machine here described works at open width and thus lends itself to continuous systems of working.

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Drying by Heat. The later stages of the removal of water are almost always carried out by the utilisation of heat and generally by the application of convection currents of air developed either by mechanical means cr heating apparatus. This requires in all cases the supplying of the latent heat of evaporation to the water driven off; it has been well emphasised in the first chapter of this work that this item is relatively very large— 966 British Thermal Units per pound vapourised—and is therefore relatively expensive. Hence the importance of reducing the water mechanically to the lowest limits before calling in the aid of heat. It is in the highest degree un- economical to get rid of water which could have been pressed from the material as liquid by afterwards being compelled to vapourise it and expel it in this form to the atmosphere ; there it is condensed and the valuable latent heat lost in the process. The tentering machine is a very bad substitute for the mangle. It is convenient to take the various convective and heating processes of drying together, and there are at least half-a-dozen scientific methods of these kinds, only some of which have so far been applied to textile drying.

1. CHEMICAL DRYING,

in which air is passed through hygroscopic substances like Calcium Chloride, Sulphuric acid, Silica gel, etc. The relative humidity is thus greatly reduced, its capacity for moisture enhanced, and it may then be circulated through or over the material to be dried. 7

2. Instead of air, superheated steam is circulated and re- circulated through the wet material ; the water is vapourised and adds to the volume of the steam. The high temperature involved precludes this process on the textile fibres.

3. VACUUM METHODS.

The boiling-point of water is the temperature at which the pressure of its vapour is equal to the external pressure, usually that of the free atmosphere. If the external pressure is reduced, the water vapourises at much lower temperatures :— : BOILING POINT OF WATER AT REDUCED PRESSURES. Pressure:— Vacuum 536 611 710 750 or : 760 m.m. 230 139 50 10 Temperature 100°C. 70 60 40 10 Or, taking a case in British units, at a pressure of 1 lb. per square inch, the boiling-point is 102°F. It is possible that drying processes based on this principle may be devised for

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textiles. The essentials are exhaust pumps or ejector devices of large capacity, possibly in series with rapid low-pressure exhausters ; and receivers of large internal volume with very strong walls to withstand the external pressure. Such methods apply to cheese and cop drying and yarns, at present a difficult problem. There would be strong cooling of the material by the evaporation.

4. CONTACT HEATING.

which is applied in drying slivers and in the common cylinder or can driers of the cotton trade. In this case there is a partial conduction of heat, which tends to bake the exterior of the fibre. It is not so usual a method on wool as on cotton. In the backwashing operation, it has been found advantageous to perforate the rollers of the cylinder drier and supply a current of warm air. Clement found that a single thickness of calico in contact with a copper plate heated by steam at 212°F. was dried at the rate of about 14 lbs. of water per square foot per hour. Chameroy found the rate to be 1.8lbs. with one thickness and 0.91 lbs. with two thicknesses of cloth passing over a cylinder. A test by Royer on twenty pieces of calico, initial weight 330 lbs., final weight 167 Ibs., loss of water 163 lbs., showed that 224 lbs. of steam was condensed in the process. Hence approximately three-quarters (163/224) of the heat was utilised. As the drying took three and a half hours, the radiation losses must have been severe. Where exhaust steam can be used for heating the cylinders, the method is very economical.

5. AIR CURRENTS. I The most general method, employed in two ways :—(a) produced by mechanical means, such as fans, etc.; (2) con- vection currents, produced by heat. The effect of setting the air in motion, irrespective of humidity changes, i.e., neglecting temperature, is probably to increase its drying efficacy ten or twelve times, as compared with calm air. It has been stated that above a wetted surface there exists a saturated layer of air more than an inch in depth in still conditions ; in drying it is therefore essential to remove this and substitute fresh unsaturated air. In the usual circumstances, therefore, both heating of the air and its mechanical displacement are required. The convenience of air as a carrier of heat arises from the fact that the atmosphere is an unlimited reservoir available at hand and at any time, and in the other aspect an equally unlimited void into which the utilised air may be expelled. But air, as a heat carrier, has grave disadvantages. The specific heat is low, about one quarter that of water, and its large volume per pound mass— i.e., its low density—makes it difficult to handle; the energy

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of motion is easily destroyed by surface friction and internal eddies. It is a bad conductor and does not readily give up or acquire heat by contact. Further, in its natural condition in the free atmosphere it always has much humidity and is frequently quite saturated. Evaporation from a wetted surface and drying takes place in the free atmosphere so long as there is less than full saturation, but in technical uses, some heating of the air is essential. At 62°F., air may hold 0.00088 lbs. per cu. ft. of moisture, but at 162°F. it can hold 0.0134 lbs. per cu. ft., or fifteen times as much. There is thus a point of maximum economy between the two factors of heat given to the drying air and volume of this displaced over the material. Data are wanting to enable this to be determined in practical cases. The two costs are :— 1. Cost of heating the volume of air. 2. Cost of power to pass this through the wet material. For maximum economy the sum of these two factors must be a minimum, and, if it were capable of practical application, a mathematical expression could be deduced for the conditions. In the existing circumstances, the results of ordinary practice are the only data available. The effects of higher temperature with consequent lower saturation have been illustrated in the chapter on Humidity. The employment of the higher tem- . peratures, e.g., beyond 120—130°F., is detrimental to wool, on account of the action on the fibre. . (See section on the Chemistry and Physics of the Wool Fibre.) The drying plants of the wool industry are undoubtedly the seat of very serious heat losses, some of which are avoidable. A strong air current through a very porous material does not become saturated to the limit indicated by its temperature ; such warm air might be recirculated. It must be noted that the water of swelling of the fibre—the imbibition water—cannot be _ instantly evaporated off like a superficial film ; time must be allowed for it to diffuse from the internal tissues of the fibres. But to allow longer times means generally increasing the size of the drying plant and greater capital costs. Conversely slow and feeble currents lack the power of penetration of the material, and energy to displace the saturated air layers. It is known to practical wool scourers that the “ cotty ’’ wool, i.e., wool with small closely tangled masses, is peculiarly resistant in the drying process. All drying processes, owing to very large latent heat of evaporation, are also strong cooling processes. It has been stated that in wool drying the amount of moisture evaporated, as compared with the steam condensed in the heater, was 12°, in other words, eight times the evaporation was needed in heating-steam. It is instructive to compare the method of the iron foundries which dry their moulds and cores in a closed chamber with just sufficient air supply and

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leakage to keep a coke stove in slow combustion.

429

This

corresponds roughly to drying by superheated steam, as in (2)

p. 425.

The special methods applicable to the different forms of material may now be described in the light of the foregoing

principles.

blending and carding departments,

Wool Drying. In some cases, the wool does not receive a special drying,

but is blown by air currents—which may or may not be warmed—along conduits from the washing sheds to the

the so-called Conveyor

system. The simplest and crudest form of wool drying apparatus is the STOVE, a room with a perforated floor, often of cast iron grids, on which the wool is spread ; from coke fires or a battery of steam pipes is passed through the layer of wet wool by the natural draught due to diminished density, or an exhaust fan is fitted. This is an example of the it is also applied in the so-called TABLE DRYERS, where a lattice, netting, grid, or open-work platform

stationary method ;

carries the wool ;

warm air

the fan may be arranged to force the draught,

in which case an excess of pressure or plenum exists in the The MOVING WOOL DRYING MACHINE has similar lattices geared to travel the wool through the machine while subjected to the air current. rotary type are employed and a tubular heater or battery of

apparatus.

steam pipes.

Fans of the pressure

Feed of wet wool, temperature, and volume of

air should be jointly regulated to leave the wool in the proper over-dried wool produces wild yarns and easily becomes electrified, while damp under-dried material works

condition ;

in the eh

The hot air should, for greater

safety, meet the wettest wool, a condition not easily obtained Some results of tests taken by McNaughts on Wool Drying plant, are given below :—

in stationary

methods.

AUSTRA- NEW tak et clea DIRTY I PONTA CLASS OF WOOL. >, I COTTY] CROSS- > SKIN I MOHAIR. LAMBS I cor, [aap I BLEND.| ARENA. WOOL. WOOL. Raw weight a .| 1000 1010 I 589 1000 800 750 1333 1200 Weight from squeezers of wool washer .. 794 977 I 625 1070 748 825 726 840 Approx. % moisture above dryness 25 24 28 26 25 27 29 28 Output of dry wool, lbs. per hour 600 744 I 451 800 560 600 516 605 Time wool in mac- hine in seconds, 65 120 75 90 80 90 75 95 Temper., Fah. 180 186 I 190 193 168 192 202 170

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Fie. 127.—HANK DRYER. (Wm. WuHITELEY & Sons, Lrp., Lockwoop, HUDDERSFIELD. )

430

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The Drying of Yarns.

The drying of sliver in the backwashing process has already been alluded to, the passage over heated cylinders, assisted by a current of warm air blown through perforations in the cylinders, being the method used. Hanks or skeins are dried by hanging on rods carried on a truck and running this into an oven with steam heat and fan Cops are placed in baskets and similarly treated, but machines with spikes to hold the cops while revolving in a current of air have been devised. Pirns are centrifuged. Material in this form is apt to give trouble by capillary creeping of dyestuff, etc., from the liquor when evaporated. Warps are dried either over large cylinders or in hot air chambers.

SINGLE CYLINDER DRYING MACHINE

ome

—~<:

Fie. 128.

The Drying of Pieces.

The mechanical drying of fabrics in piece-lengths, 30 to 60 or 100 yards, is carried out by the Mangle, the Hydro-Extractor or the Open Width Vacuum machine in the first stage. The final drying is effected either on the Cylinder machine or on the Stenter (Tenter).

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The Cylinder or Can Dryer consists of a series of hollow rolls which are warmed internally by steam ; these may be erected in vertical sets or in a horizontal series. A scutcher or ex- panding mechanism is used to open the cloth out from the rope form, and a cuttling or folding gear may be attached to the delivery end. It is the favourite machine in the cotton trade, as the hard and smooth finishes of most cotton cloths are, if anything, assisted by the contact with the heated metallic surfaces of the cylinders. Its effect is to produce a kind of ironing-out of creases and cocklings, but in wool it gives a harsh and dry handle, known to the workmen as ‘baking.’ It has the great defect as compared with tentering that the piece width is not under control ; but cylinder drying, being simple, rapid, and economical, is often used in inter- mediate stages where a subsequent steaming, etc., will remove the caking and stiffening effect. In some cases cylinders faced with aluminium sheet are desirable to prevent staining.

THE CELL DRYER

consists of a series of hollow rectangular plates arranged in a vertical pile with interspaces ; a system of rollers at the ends traverses the cloth through each space in turn. Each plate is steam heated, the total effect being very powerful. This device is intended to economise heat, as compared with the cylinders, where losses by radiation are enormous.

CHAMBER DRYING

or ‘‘ stoving ”’ (a word also used to indicate sulphur bleaching) is used for fabrics with considerable pile, as rugs or curls (astrachans), plushes, etc. The cloths are hung upon vertical tenter frames and a circulation of air forced between by fans.

The Stenter or Tenter.

This machine is distinguished from other drying appliances by the fact that the cloth is held along the lists by pins or clips while being dried out, and the cloth thus receives a ‘* setting,’ folds and creases being pulled out evenly, and the warp and weft put into the proper geometrical relations. This arises from the saturated and consequently swollen state of the fibre, which as the pieces come to the tenter will contain 40-60°% of water. The machine will ordinarily deliver the cloth with several per cents. less than the normal regain, probably 8-10% regain, though exact data of this kind are wanting. The tenter, like the blowing machine, sets the texture in addition to its drying function.

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Fre. 129.—AUTOMATIC TENTER FEED

(CANBY & FAaARRarR, HUDDERSFIELD. )

EE

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There are many differences of detail in the construction of tentering machines, but the leading elements are :—

i:

Two parallel chains carried in guides on the machine frame, the links of which have combs carrying the tenter pins, or alternatively special clips, the jaws of which by spring and toggle actions grip the edges of the cloth firmly.

2. At the feed end, rollers and twitch rails, with special

guides to pass the cloth to the pins or clips ; circular brushes help to press the fabric firmly down the pins. If clips are used, cams or other devices are used to open them at the appropriate point to receive the cloth. Twitch rails, etc., are fitted to apply “drag” to a cloth which is required to retain its length.

HOT ATR PRINCIPLE.

Fig. 130.—TENTERING & DRYING MACHINE witu COLD AIR FAN.

(WM. WHITELEY & Sons, Lip., Lockwoop, HUDDERSFIELD.)

3.

Or

Rollers ; to reverse the direction of travel of the cloth at the ends. These are telescoped to admit of variation of width. Screws ; carrying the side frames and chains. These widen the tenter so as to permit different widths of fabric to be handled, or within limits to stretch the cloth weft-ways. Cuttling or folding gear, to take the cloth from the stripping rollers and lay it into a pile. Heating arrangements. These take different forms, as tentering machines may be broadly divided into two types :—(a) HOT-AIR, (6) STEAM COIL. In the hot-air type a current of warm air is blown by a pressure

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fan between the several layers of cloth. The heater is either a battery of steam pipes enclosed in casing attached to the fan case, or a modified locomotive type in which the tubes carry the air and are surrounded by the steam in the cylindrical shell. In steam coil tenters, flat coils of steam pipe about one inch bore lie between the layers of cloth ; by the hot-air rising from them and their radiation, the moisture of the cloth is vapourised. 7. Measuring arrangements, to indicate to the tenterer the proper width and length of the tentered pieces. 8. Motive power; which may be a small independent engine, cone belt drive, or electric motor, but in any case should be arranged for variable speeds.

THE PRACTICAL ROUTINE OF TENTERING.

The pieces, if not fed through a scutcher, must be evenly cuttled and their ends sewn by machine with short stitches ; it is easy to produce creased and distorted ends by loose stitching, especially when much pull is put on to keep out the length. The tenter must be set 2-3 inches over the finished widths in worsteds, while the felted structure of woollens permits more stretching, if so desired; if much “ braiding ”’ or pulling in width is practised, the cloth must be correspond- ingly wetter. Over-pulling means weakened or torn lists ; in the length it may produce a streaky effect. To a certain small extent warp pull and weft pull are interchangeable and compensating. In steam coil tenters, stoppages should not be too long or curious markings appear; small shifts of 2-3 feet or so may be given between stops if the cloths are very wet and cannot be run continuously. The machine must be marked so that the tentered length can be observed, and scales fitted for recording the tentered width. If the cloth is entered too slackly, it may, when drying out, slip off the pins; this may be checked by wooden rails carried just inside the chains ; their edges a little higher than the level of the pins. Also, the pins should be set in the combs with a slight lean away from I the upright position. Before starting up the tenter for the day’s run, it should be warmed thoroughly to prevent rapid condensation and drips from the cold metal when the drying: of cloth begins. Great care must be taken in oiling the. machine, especially the chain, because of the danger of greasy flock falling on the fabric ; practical opinion seems divided! between the merits of a good tallow and a proper quality of machine vaseline, but the main point is to avoid excess of either. A tentered piece will in about 10-12 hours, on an. average, recover 10% regain.

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436 THE HEAT BALANCE SHEET IN TENTERING.

The tentering process, particularly in the hot-air type, is a convenient occasion to discuss the subject of drying by con- vection currents of air, a method of extended utility in textile

work. Air which is used for drying in this way must serve three ends :— I 1. The air must give heat to the material to raise its temperature to a height favourable to quick evaporation.

Fic. 131.—TENTER, WITH COCHRANE’S SUPERHEATER.

(WM. WHiTELEY & Sons, Lrp., Lockwoop, HUDDERS/IELD.)

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Fie, 132.—HOT-AIR TENTERING MACHINE. (WM. WuiteLry & Sons, Lrp., Lockwoop, HupDERSFIELD.)

437

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In wool this must not be excessive, especially on dry wool. Hot air for tentering is generally limited to between 120-160°F. In comparison with the next item, the heat of evaporation, this first quota of heat is negligible ; if necessary, it could be calculated from the specific heat of wool and the temperatures. 2. The air must communicate to the water dried out from the material the latent heat of vapourisation, in c.g.s. units 540 calories per kilogramme of water. This is the principal item. 3. The air, having now supplied heat to warm the material and evaporating the water must absorb it as aqueous vapour ; its temperature on exit must be sufficiently high to carry the necessary quantity of humidity, even if at saturation. The minimum yolume of air at the lowest possible entering temperature should leave with the highest possible humidity, i.e., with the greatest weight of extracted moisture.

HEATER DRYING ROOM

ENTRY FAM An! EXT Far uJ 5 ” Oo Oo Z be AH PEP ED

HEAT CYCLE OF WHOT-AIR TENTER Fic. 133.

The Hot-Air type of tenter is purely a convection heating appliance, and is a suitable starting point for the study of this form of textile drying process. Let Fig. 133 be a diagram- matic representation of the arrangements. The entry fan takes the required volume of air from the external atmosphere at a certain temperature, pressure, and humidity. This is delivered to a heater becoming a new volume at a higher temperature, and is then passed forward to the tentering machine. Here the hot air is blown through the stretched fabric, removes from it a certain weight of water—leaving an amount usually much less than the standard regain—and is then expelled from the room to the external atmosphere. At this stage it has reduced its temperature and altered its volume correspondingly, also increasing its content of moisture. It

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may be assumed during the cycle that it has preserved a constant weight—entry and exit—and this is a convenient basis for calculation, the mass and volume being readily convertible by the ordinary laws of gases. In the first instance, the entry air will be taken as saturated—becoming unsaturated after passing through the heater—and further supposed saturated again at the lowest temperature of rejection. The equalities characterising the cycle are :—

Heat lost by Entry Air + Heat lost by Entry Aqueous Vapour = Heat Used in Evaporating the Material; and Difference in Moisture Content at Entry and Exit = Weight of Water Evaporated.

From these an equation can be deduced in which the following are the given data :— 1. The weight of water to be evaporated. 2. The highest temperature permissible in the entering air. 3. The temperature of the intake, i.e., of the external air.

The weight of air required—and consequently its volume— the exit temperature for the humidity, etc., may then be found and the problem completely determined.

In the average textile case the weight of water to be evaporated may be assumed to be 50-60% of the loom weight of the fabric ; as received by the scourer they have standard condition, about 15%, and the .tenter does not deliver an absolute dry cloth. The highest permissible temperature actually on the wool should not be above, say, 110°F. on the dry wool, but it may safely be much higher, 140—-160°F. on the wet pieces. Even higher temperatures are used in drying scoured wool. The external air has a variation of temperature from the freezing-point or less, 32°F. in winter to 86°F. or 30°C. in summer, and its humidity at intake may be anything from 20-100%, being commonly about 75%. The upper limit of say 150°F. imposed by the necessity of not scorching or over-drying the wool is a severe check on the efficiency of drying by means of warm convection currents. Theory shows that the entry air should be as hot as possible. The steam heater employed to raise the temperature of the incoming air functions at 212°F., or slightly over, and its condensation water is not usually much below boiling-point. As an illustra- tion, if it is required to evaporate 100 kilograms of water with air at (a) 40°C. or 104°F., or (b) 60°C. or 140°F., all other conditions being the same, more than three times the volume of drying air would be required at the lower temperature. to carry off the vapourised water and several per cents. more expenditure of heat. At 90°C. about one-half the volume is needed, as compared with intake at 60°C. But attempts to use very hot air lead to over-rapid evaporation from the

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surface of the fibre, as compared with its interior, and the resulting baking of the wool. Obviously, if it were possible to tenter in two stages, the first with very hot air on the wetter cloth, adding a new volume of cooler air at the second stage, some economy of heat would be possible. Comparison of two cases of evaporation by air at 60°C. on entry and (a) 20°C., or (6) 5°C. on exit shows that while in the second case about 11% smaller volume of air is required, nearly 20% more heat for vapourisation is necessary. Thus the working at the low temperatures is less efficient than in summer, when the average temperature of the entry air is much higher. The volume of the air of the tenter cycle is smallest at the intake, is a maximum of heating, and is reduced to an intermediate value on exit. In hot-air tenters the fan is placed before the heater and a slight pressure is produced in the drying chamber; this plenum is, on the whole, un- favourable to evaporation, but the fan is moving the minimum volume of air. In other types of tenter, e.g., the steam-coil variety, the fan should be placed at the exit to produce a slight vacuum. But these effects must be of a minor order. It is easier to control the air in respect of cleanliness on the plenum system. The time of drying is a quantity exhibiting much eae: depending on the heating arrangements of the tenter, the texture of the cloth, its wetness, etc. ; the linear speed in the machine may be from 10-30 feet per minute in average practice. In the drying room a slow motion of the hot-air current is desirable. The rule in textile drying by tentering is to subject the wettest material to the hottest and therefore driest air, i.e., the wet cloth and hot air enter at the same point. This is the inverse of the usual practice in drying operations on many other materials, but it is sound theory on wool, which must not be exposed to overheating or undue dessication. The time of drying is plainly shorter when a maximum surface is exposed to the heated air currents, and while this is a fixed factor in the case of tentering piece goods, it is capable of being governed very closely in wool drying by the travelling lattice hot-air machine. Theoretically, the exit air containing much moisture has a smaller density than the air at entry into the drying room, but the temperature of the air from the heater is so much higher that the moisture factor is over- weighted ; the incoming air is always lighter. If a vertical tenter were designed—and there would be certain advantages in such a type—it would be necessary to pass the hot air from above, downwards. It is possible—but actual experimental investigation on tentering problems is lacking—that the tenters which are arranged in tiers use heat more efficiently than those extending in one Jayer only ; in average tentering,

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the air is by no means worked up to its carrying capacity for moisture. The heat problem in tentering may be illustrated by the following example :— REQUIRED, to remove 100 kilogrammes of water from cloth by means of air of which the maximum temperature in the drying room is not to exceed 70°C. (158°F.); the external air is at 20°C. and is three- “quarters saturated and the exit air is half saturated.

The incoming air, three-quarters saturated at 20°C., would correspond to saturated air at 15°C., and calculation gives 29.75°C. as the exit temperature. The total weight of drying air required would be about 6450 kilos. From this, its volume at the temperature of admission can be found, the fan capacity necessary and the quantity of heat to be given to the air. But these calculations, in the absence of experimental work, cannot be pushed too far. Until this work is carried out, many special tenter questions and problems must remain unsettled.

A table of data for propeller fans is appended :—

DIAMETER. SPEED RANGE. OUTPUT RANGE. ins. revs. per min. cu. ft. per min. 20 760-1265 2110-3510 30 510-840 4780-7875 36 425-700 690-11340 48 320-525 12290-20160 I * * * * * * * * * TANDEM SQUEEZER. SINGLE SQUEEZER. PIECE OF OVERCOATING FROM PIECE OF OVERCOATING FROM LOOM 42. Loom 128. Weight of piece—Dry ibs. Weight of piece—Dry state 128 state — 125 » saturated 256 » saturated 250 , After squeezing 195 ,, After squeezing 200 Moisture taken out by Moisture taken out by Squeezer 61 Squeezer 50 Total moisture in cloth Total moisture in cloth before squeezing 128 before squeezing 125 °, Efficiency 47.65% ïficiency 40% Result :—

Tandem Squeezer takes out 19.125°% more moisture than the Ordinary Single Squeezer.

THE MECHANICS OF HYDRO-EXTRACTORS.

The relative efficiency of the three systems of mechanically extracting the moisture out of textile fabrics has been in- vestigated by Grothe, who gives the percentage of water removed in fifteen minutes as :—

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RELATIVE EFFICIENCIES OF SQUEEZING MACHINES, WRINGING MACHINES AND HYDRO-EXTRACTORS.

YARNS. WOOL, SILK. COTTON. LINEN.

Wringing 44.5 45.4 45.3 50.3 Squeezing 60.0 71.4 60.0 63.7 Hydro-extracting 83.5 77 81.2 82.8 PIECES. Wringing 33.4 44.5 44.5 54.6 Squeezing 64 BGT 72.2 83 Hydro-extracting 77.8 75.5 82.3 86

It is evident that there is general superiority in hydro- extracting.

The principle of the hydro-extractor consists in creating a centrifugal force upon the material within the cage; this depends entirely on the diameter of the cage and the revolu- tions per minute. There is a limit to the amount of centrifugal force permissible, varying with the strength of the material of which the cage is constructed. If the speed were to be increased to an indefinite amount, this would cause it to burst, due to its own inertia, even if no load were in it. It is owing to this fact that the peripheral speed cannot exceed a pre- determined figure, and consequently hydro-extractors must not be run at speeds greater than those specified by the makers, otherwise they become dangerous. Properly used, they are among the most permanent and economical in maintenance costs of finishing plant.

The steam-driven type of hydro-extractor has been widely employed in the trade, and is only gradually being displaced where electricity is available. These machines are direct- driven by a small steam engine attached to the casting forming the base of the outer case. They have the advantage of exceedingly quick acceleration, but on account of the recipro- cating motion, wear and tear are liable to be excessive, and hence maintenance costs higher than in other cases. Having many working parts, a good deal of supervision is necessary, and there should be periodical examination for loose lock nuts, worn bushes or bearings, etc. The engine is of the ordinary Single Cylinder type, with a flat slide valve set about 1/3 cut off ; it works at any steam pressure, from 30 lbs. per sq. in. upwards, but, of course, the higher the steam pressure the quicker the acceleration will be. At 80lbs. pressure the hydro-extractor will get to full speed in less than one minute. The steam and exhaust connections to the cylinder have to be flexible pipes, to allow for the oscillation of the machine, and the exhaust pipe should have a downward fall from the engine, to enable condensed water to drain away. Care should be taken to open the drain cock of the cylinder before starting up,

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443 especially if the engine has been standing for a few hours, otherwise there is a danger of the cylinder end being broken, due to the accumulation of condensed water. The Broadbent suspension on three short columns by means of hanging bolts with spherical ends, is an important detail, permitting the loaded cage to rotate round the new centre of

@

Fic. 134.—STEAM-DRIVEN HYDRO-EXTRACTOR.

(T. BRoADBENT & Sons, LtD., HUDDERSFIELD. )

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gravity during accelerating and while running, and even allowing a reasonable out-of-balance load. When installing a new steam-driven machine, it is advisable to run it without load for short periods after erection, to enable the bearings to bed down and to ensure the erection having been carried out correctly. Run the machine at a slow speed for the first five minutes and then gradually accelerate it to full speed. During the trial run, check the revolutions by the speedometer, and if this is excessive the steam throttle valve must be screwed back until the correct maker’s speed is attained. It is very desirable for a check valve to be fitted on the steam main to control the maximum supply of steam admitted to the engine cylinder and thus prevent dangerously high speeds. Hydro-extractors are now commonly fitted with centrifugal clutch pulleys. In starting up various resistances have to be overcome, the chief of which is the inertia of the basket and load ; in addition, we have some bearing friction and air resistance, which increase with the speed. In a belt-driven machine, starting up from a solid pulley on the countershaft there would, owing to these resistances, be considerable belt slip before picking up the load, and hence there would be abnormal wear on the belt. The centrifugal clutch pulley consists of two parts, an interior spider keyed on to the countershaft and an outer belt pulley running loose on the spider sleeve. The spider has four pockets, each containing a loose shoe lined with ‘* Ferodo immediately the counter- shaft is set into motion, these shoes are thrown radially outwards by centrifugal force and press against the interior rim of the belt pulley. As the speed of the countershaft rises, the pressure of the shoes increases until there is sufficient to put the belt pulley into rotation and enable it to start and drive the machine. By means of these slipping shoes, there- fore, the hydro-extractor is very gradually brought up to full speed without any belt slip and without any sudden jar or shock ; when the machine attains full speed, all slip in the clutch ceases and the drive becomes positive, as in a solid pulley. Undoubtedly, the electrically-driven under type is the ideal machine for the purposes of the cloth finisher, in general convenience, efficiency and also in running and maintenance costs. The absence of belts eliminates the annoyance of broken belts, slipping off pulleys, slack drive, wear, etc. Similarly, there are no steam joints or leaky pipes, no packings to replace, and lubrication is constant and regular. Like the motion of the hydro-extractor itself, the electric motor has a rotational motion. This motor must have a characteristic showing a high starting torque and a reasonably low starting current ; it should be of robust construction, to withstand the

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rough conditions, and of high rating on account of the frequent starts, and for similar reasons drives through a centrifugal clutch. The advantages of these arrangements are :— (a) The starting up of the machine is quite automatic. (6) The attendant cannot damage the motor by oe on the current too suddenly. (c) The starting current never exceeds a maximum figure definitely fixed for the particular machine. (d) The drive becomes positive after about 75% of the full speed has been attained. The accelerating times vary for the direct current machines from 14 to 5 minutes, and with alternating current machines from 4 to 24 minutes, according to supply conditions. The A.C. motors are of the totally enclosed type, having squirrel cage or short circuit rotors. It may be noted, in passing, that the Electrical Commissioners have recently decided that 400 volts, 3 phase, 50 cycles is to be the recognised British Standard Current Supply for new plant in this country, and in the future there will be the advantages of standardisation in this direction. — The cages or baskets of hydro-extractors are modified in textile practice according to circumstances. The galvanised mild steel cage is very commonly employed, being constructed from boiler plate having a tensile strength of 28 to 32 tons per square inch; welding, instead of rivetting, is modern practice in building these cages. Copper cages are often used in carbonising plants, but the mild steel type, coated with vulcanite, is superior.. Tinned copper cages are considerably weaker and less permanent. It must not be thought that the holding capacity of a hydro-extractor is in direct proportion to the diameter of the cage, thus a 72 inch cage may have a capacity of 43 cubic feet, while a 36 inch cage may only have a capacity of 11 cubic feet. Note that the capacity is always reckoned on the dry weight of the material and not the weight of the material which can be put into the cage, which latter is obviously an indeterminate figure. Thus, if the dry weight capacity is given as 200 lbs., and the material contains 100% of water before ext:acting, it is possible to put in 400 lbs. of wet material. Always pack the material round the rim first and then work towards the centre, until the cage is completely full. It is a good practice to tuck a strong canvas or sail cloth over the goods, with the edge under the lip of the basket ; if covers are used—a doubtful advantage—they should be of strong wire mesh. Deep cages have greater capacity, but are inconvenient in loading and particularly unloading. The 72 inch diameter, of shallow type, is the most popular textile machine. Outer cases are best made of mild steel ; cast iron is dangerous and should be abandoned. For carbonising,

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bleaching, chlorination, etc., they should have an interior lining of lead flashing. The speed of a hydro-extractor depends on the diameter of the cage, and consequently the speed of each size of machine varies. The safe speed is entirely dependent upon the strength of the cage shell, and no great advantage is derived by in- creasing the thickness of this. The weight of the shell itself has to be taken into account, and even in an unloaded cage there is a certain critical surface speed at which bursting will occur, this being independent of the thickness of the shell or its diameter. The total stress on the shell is plainly that due to the radial pressure added to the self-stress. For steel cages, this is not allowed to exceed about 6 tons per square inch, 1.e., the factor of safety is approximately “5” times. Ina 72 inch machine, at 650 r.p.m., giving an extraction force of 432, the surface speed of the rim is 12,242 feet per minute ; in a machine, at 1,000 r.p.m., giving an extraction force of 512, the surface speed will be 9,418 feet per minute. Thus, though the larger machine has a much greater surface speed than the small machine, the smaller machine has a beiter extracting force. This shows that smaller machines are better driers than the larger machines, but this is no advantage when treating textile materials as about 400 “ gravities ’’ stress is quite sufficient to overcome the skin tension of the water on the fibres. Large machines, with greater holding capacity, are preferable on commercial grounds. Hydro-extractors are usually fitted with a circular brake band, lined with alternate blocks of ‘‘ Ferodo”’ and poplar wood and tightened by a hand lever ; the brake should not be applied too suddenly, as the contents of the cage may slide or creep, and cause damage on sensitive fabrics. I An interesting and important consideration in the practical working of hydro-extractors is the time of running, i.e., the useful duration of the application of the centrifugal force. An instructive table, compiled by the Chemical Department of the Northern Polytechnic Institute, is appended :— TABLE OF APPARENT EFFICIENCIES OF HY DRO-EXTRACTORS.

TIMES. SPEEDS (R.P.M.) (MINs.) 100 124 197 - 330. ss 368 476 607 1,198 0.5 — — — — — 10.0 14.2 18.0 35.0 10 — — — 18.1 15.8 20.1 25.0 46.5 55.3 2.00 — — 18.5 24.5 29.6 34.4 46.7 50.0 65.4 3.0 =— 9.4 25.0 31.1 37.1 48.0 56.1 64.5 69.2 4.0 — — 30.8 36.7 44.3 48.4 60.8 67.0 70.5 5.0 — 18.4 34.9 40.3 48.6 52.4 63.0 68.9 71.7 7.56 — 17.4 40.4 49.9 57.0 59.8 66.8 70.5 72.0 10.0 7.2 20.4 44.8 56.5 60:8 66.5 69.3 71:1 72.56 15 10.8 27.6 52.5 64.8 68.6 70:6.70.9 71.4 73.5

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These experiments were carried out on chemical crystals and will, of course, vary according to the gravity factor and the material dealt with. It may immediately be deduced that :— (a) The length of time the material is ‘‘ whizzed ”’ is of no advantage after a certain period. I (6) Also that increased speed above a certain amount is not of very great importance. Let us first consider “‘ whizzing’ time. From the table a speed of 1,198 revolutions per minute corresponds to an efficiency of extraction of 71.7% after the first 5 minutes, whereas after 15 minutes this has only been increased to 73.5%. Thus an increase in the duration of running time by 10 minutes has yielded an extra drying efficiency of only 1.8%. It is seen that after 5 minutes’ run, practically the whole of the water has been extracted, and probably the slight increase in efficiency is due to air circulation than to longer whizzing. Now consider increase of speed, and take, for example, a 5 minutes’ run. At 1,198 revolutions per minute the efficiency is 71.7, and at 697 r.p.m. it is 68.9. Therefore, by increasing the speed an additional 500 revs. the efficiency has been raised only 2.8%. Hence, generally, the slight additional drying obtained by high speeds or long durations of running is not worth the extra power cost, the additional wear and tear, and particularly the loss of time and output. Woollen piece goods after scouring or milling usually contain more than twice their own weight of water, and 74 minutes of hydro-extracting or so will reduce the residual moisture to about 40%. The residual moisture of worsted piece goods is slightly in excess of this; woven or knitted cotton goods usually retain about 40 to of moisture, and woven or knitted silk or artificial silk (rayon) fabrics from 70 to 78%. It is not uncommon to find so-called tests conducted on hydro- extractors by the procedure of collecting and weighing the amount of water extracted and comparing this with the water left in the material, to arrive at a percentage figure. This 1s an obvious fallacy, as it depends on the amount of water in the material before “‘ whizzing,’ a quite casual and fortituous figure; a hydro can be equally as efficient when drying a fabric containing three times its weight of water as with a fabric containing less than its own weight of water. In each case, the residual moisture should be nearly the same, for each class and quality of material, and therefore the efficiency must be based upon the moisture contents after “‘ whizzing,’’ this being always a definite percentage of the dry weight. Another delusion among workmen is the practice of running the machine until the drip from the spout actually ceases. As shown in the numerical examples given above, this leads to excessive running time ; often this drip is merely the drainage from the

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interior of the outer case. When “‘ Commercial Dryness ”’ has been achieved it is in all senses a waste to continue running until ‘“‘ Possible Dryness” is attained. Mills working on definite classes of goods should carry out a few simple trials by extracting and weighing the material, timing the duration of the runs, and calculating a percentage for a standard of regular working. What pressure is exerted on the material during extracting ? If the load is a mass of definite mechanical properties, such as water, this is a calculable quantity. Thus, assuming a cage 60 inches diameter, running at 750 r.p.m., and containing a wall of water 4 inches thick, the pressure exerted on the interior of the shell of the cage would be 65 lbs. per square inch. Increase of the thickness of the mass will increase the pressure and if the cage were filled up to the edge of the lip— thus giving a thickness of 64 inches of water, the pressure would be increased to 100 lbs. per square inch. In the case of textile goods, however, we have another instance of an indeterminate problem, owing to the want of knowledge of the elastic properties and the varying density of packing, etc. For example, a cage holds considerably more weight of wet cotton than wet wool, the cotton when wet becoming hard and packing more closely than the springy wool. But as cotton has an increased retentive power for water, it requires a longer running period than wool. Various factors affect the question of output, e.g:, a greater weight of cotton may be dealt with per charge, more charges of wool are obtained per hour ; further, it requires more packing time for cotton than wool, there being more material to put in. A similar consideration applies to the removal stage, the cotton being denser after the whizzing. Probably three charges of cotton and four charges of wool can be obtained per hour. In a large works, the best system is to instal hydro-extractors in pairs, so that charging and running may alternate, thus eliminating waste of time.

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THE CHEMISTRY AND PHysSICcs

OF THE Woo. ET'IBRE.

FF

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CHAPTER XII. The Chemistry and Physics of the Wool Fibre.

The Chemistry of the Wool Fibre,

Wool is a substance belonging to the domain of organic chemistry :—

1. Because it is a product of a living organism. 2. Because also in the narrower definition of the chemist, it is a complex compound of carbon.

In the raw or unscoured state, wool may contain as much as 50% of impurities, comprising :—(1) Wool Fat, an impure lanolin; (2) Suint, the wool perspiration, largely potassium carbonate; (3) Vegetable matters, seeds, burrs, fibre, etc., removed by carbonising; (4) Earthy matters, sand, etc. When scoured, the wool fibre is composed ultimately of Carbon, Hydrogen, Oxygen, Nitrogen, and notably Sulphur ; this last is its distinction from the other textile fibres of animal origin, e.g., silk. The nitrogen and sulphur, along with its general chemical characters, establish wool among the Proteids or Proteins, to which belong albumen, casein, gelatin, gluten, etc. The work of Emil Fischer and his pupils has shown that the protein molecule is built up of a series of Amino-acids forming the “ polypeptides ” of Fischer ; other groups, phosphoric acid and perhaps carbo-hydrates may be added to this essential grouping. Proteins are therefore open or closed chains of amino-acids linked by the carboxyl group of the one to the amino group of the next with elimination of OH,. The open chains are amphoteric, basic by their terminal amino group and acid by their carboxyl group. Under the action of acids, alkalies, superheated steam, digestive and other ferments, or bacterial action, cleavages occur. ‘“‘ When the protein mole- cule is broken down in the laboratory by processes similar to those brought about by the digestive enzymes of the alimentary canal, the essential change is due to what is called HYDRO- LYSIS ; that is the molecule unites with water, and then

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breaks up into smaller molecules. The first cleavage products, the ‘ proteoses,’ retain many of the characters of the original protein; the same is true, though to a less degree, of the ‘ peptones,’ which come next in the order of formation ; the peptones in their turn are decomposed into short linkages of amino-acids which are called ‘ polypeptides ’; and finally, the individual amino-acids are obtained separated from one another.”’ (Halliburton, 1916.) Fischer says :—‘‘ The amino- acids are the base constituents of the proteins, being linked up therein by an amido coupling.”’ It must be noted that of the purely theoretical chemistry of the protein molecule summarised above, little or nothing has been applied, at any rate in the case of wool, in technical practice. Wool is a member of the sub-group KERATINS, belonging to the SCLERO-PROTEINS, and is chemically related to hair, horn, hoof, feathers, etc.

KERATIN

is characterised among the proteins by its great insolubility, and its high percentage of the sulphur-containing amino-acid Cystin. It exhibits the following reactions :— 1. Xanthoproteic test, i.e., the yellowing by nitric acid, which is well marked. The yellow colour is due to a nitro compound of some aromatic body (Tyrosine 2). Millon’s mercury-nitric acid reaction ; well-marked in keratin, due to tyrosine. Glyoxylic reaction (Reduced Oxalic Acid), is also well marked ; said to be due to Trytophane. Sulphur reaction (Sodium Plumbate) ; well marked, due to high Cystin content. 5. The Biuret test—sod. hydroxide followed by copper sulphate—does not succeed owing to insolubility.

THE VAN-SLYKE REACTION.

Free amino groups of aliphatic type, when treated with nitrous acid, liberate nitrogen as gas :— R.NH, + HNO, = R.OH + N, + H,0. This method is now employed to determine the distribution and partition of nitrogen in the protein molecule. No deter- mination appears to have been made upon Keratin, but in gelatin there is only about 3% of the total nitrogen present as free amino groups in the unhydrolysed protein. This has a direct bearing upon the question of the acid-combining capacity of the protein molecule.

HYDROLYSIS.

Now when hydrolysis by acids or alkalies takes place, the elements of water are taken up, and the various amino acids

~ ae

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separated. Thus a scheme of the protein decompositions might be set out as follows :— Complex Proteid

Complex Protein Protalbumoses Heteroalbumoses Pas Polypeptides

Amino-acids Ammonia, fatty acids, phenols, alcohols

Nitrites

Nitrogen

Nitrates

Upon hydrolysis the peptides break down into their constituent amino-acids, the imino groups in the polypeptid molecule being converted by the taking up of water into amino groups. It may now be regarded as established that the protein mole- cule is a catenary or chain linkage of amino-acids attached by the amino group of one to the carboxyl group of another :— H,N.R,.COOH + H.HN R,COOH = H,N.R, COHN R,COOH + H,0O. If this reaction is reversed as in hydrolysis, there follows the transformation of an amino or potentially imino group into a free amino group. The question immediately arises as to the mode of linkage of the amino acids within the protein complex. It is certain that the type of union obtaining is that known as the “‘ peptide viz. :— —CH,—NH—CO— This peptide linkage is obviously formed by the condensation of the Carboxylic (COOH) group of one amino-acid with the. Amino (NH,) group of another amino-acid. It is most probable that the neutralising power as regards both acids and bases resides in this linkage, and not, as hitherto commonly believed, in the terminal amino and carboxyl groups. If this is recognised, many apparent discrepancies in the action of acids, alkalies, dyestuffs, etc., become explicable. It is unquestionable that the elements in the protein molecule actually concerned in the union with acids are largely the —COHN— groups, and a similar remark probably applies to alkaline reactions.

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S. H. Higgins (Reports of Progress of Applied Chemistry, 1917, p. 100), says :—

** The reason why textile chemistry is so difficult and depends so much on experience is because the chemist is dealing with substances or mixtures of substances the chemical constitutions of which are unknown. For instance, raw vegetable fibres contain, as a rule :— 1. Cellulose, concerning which a large amount of research has been performed, but no definite ideas formed as to its constitution. Waxes, the thorough investigation of which has only recently been commenced. Proteins; their chemistry is extremely complex, and their constitution far from determined. Proteins, concerning which little is known. Colouring matters, of undetermined constitution. . Mineral matter. This collection of substances of unknown chemical constitution serves. to indicate why the industry was founded on empiricism rather than on a scientific basis.”’

Exactly parallel observations might be made in the case of wool and the animal fibres.

Very little special chemistry of a constitutional kind has been done upon keratin, and it is therefore necessary to proceed. by analogy with the general proteins. Our technical processes, so far as they can be based on known scientific principles or data, presuppose a knowledge of constitution, and the principal reason for the introduction of this very abstract chapter is the necessity of collating the little work hitherto done in wool chemistry and emphasising the need for further effort in this direction.

Sok Ls

REACTIONS OF PROTEINS.

The amphoteric character of the proteins interferes with direct titration by acidimetric methods; the simultaneous presence of both acidic and basic elements and the fact that many of the indicators enter into combination with the protein —disturbing the equilibrium or displaying abnormalities— makes titrations indeterminate or impossible. When the proteid is almost insoluble, and when experiments are con- ducted upon extractions or mere suspensions, the utmost care is necessary in making deductions as to acidity, basicity, neutrality, chemical combination v. absorption, etc., of the parent substance. Thus litmus paper dipped into a suspension of Casein particles in distilled water is reddened where it is touched by the undissolved particles, while the fluid which bathes them remains clear and neutral. Evidence may be adduced to show that the salts which proteins form with inorganic acids and bases do not dissociate at the point of union of the inorganic radical with the protein, but elsewhere within the protein molecule itself; thus yielding, not an inorganic and a protein ion, but two or more protein ions, in

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one or more of which the inorganic radical is bound up in a non-dissociable form. (T. B. Robertson.) Proteins, by the opening up of fresh peptide linkages, tend to maintain the approximate neutrality of their solutions.

AMPHOLYTES OR AMPHOTERIC

substances have the dual property of combining with both acids and bases to form salts. Thus glycin (amino-acetic acid) forms a sodium salt CH,.NH,.COONa, and a hydrochloride HCl. NH,.CH,.COOH. In neutral solution it is a feeble electrolyte partially dissociated. The proteins are generally amphoteric. Keratin (wool substance) is known by its general reactions with acids, bases, salts, and dyestuffs to be amphoteric. It has already been noted that it is very improbable that terminal —NH,. CH or COOH groups are concerned in these reactions ; the active agents are the COH.N groups within the protein molecule.

As much as 70% of the theoretical yield of a protein has been obtained in the form of amino-acids, proving that the protein molecules are built up of conjugations of these. Hofmeister has suggested an elimination of water between the carboxyl and amino groups, thus :— R Ry Ry Rj I spin, a

I COOH.CH.NH H OH CO.CH.NHH OH CO.CH.NH H OHCO.CH.NH To give a body of the general formula :— R R, R, R

3

I I COOH.CH.NH—CO.CH.NH—CO.CH.NH—CO.CH.NH,

where, in the case of Keratin (wool substance) R, R,, R,, R,, Ry, . . . . R,, are groups of the types cited below, being according to Abderhalden’s analysis of 1907, principally Alanine, Valine, Leucine, Tyrosine, Cystine, Proline, Aspartic Acid, Glutamic Acid, etc.

A primary analysis by Abderhalden (1907) of keratin from sheep’s wool gave :— .

Glycine 0.6 Serine 0.1 Alanine 4.4 Cystine 1.3 Valine 2.8 Proline 4.4 Leucine 11.5 Aspartic A. 2.3 Phenylalanine 2 Glutamic A. 12.9 Tyrosine 2.9

totalling 49.2% of the molecule.

It is not possible in the present state of proteid chemistry to make a complete primary analysis of wool ; nor yet is there a close agreement between different analyses or various

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observers. Further, the products already isolated are not sufficiently well characterised in their distinctive properties or reactions to give any basis for technical methods or processes. It is not yet possible, for instance, to locate the natural colouring matter of wool in any one or even a few of these components ; and the several actions of oxidation, reduction, diazotisation, and special reagents are at present not located as regards the components of the wool molecule. It may not even be a possibility to isolate a standard Keratin which shall represent the chemical mean corresponding to the textile fibre :—WOOL.

There have been infrequent attempts to obtain selective effects on particular constituents of the wool molecule without much tangible result. Messrs. Fort and Lloyd, “On the Development of the Amido Group in Wool ”’ (Jour. Soc. Dyers and Colorists, 1914, p. 73).

The authors used the potassium salt of B-naphtho-quinone- 4-sulphonic acid, which forms golden yellow needles soluble in water, is extremely reactive, and condenses with a variety of simple amido compounds, giving coloured condensation compounds. All primary aromatic amines, e.g., aniline, condense. The brown compound with wool becomes reddish brown in a trace of acid, olive brown in alkali; reduces in hydrosulphite, and returns in air. (Cf. reoxidation of indophenol.) Treatment of wool with hot dilute alkalies increases the reactivity with the quinone sulphonate; at the same time an increase of affinity for a dye like Bordeaux B (an acid dye containing acid groups only), is shown. Hence alkaline treatment, caustic or carbonate, hot or cold, appears to develop free amido groups in the wool substance. In general, the hydrolysis of wool by acids or alkalies develops free amido groups, provisionally :—

W > W Se ee ee ee NH—CO —<———_ oe NH,—COOH Gelmo and Suida considered that the wool substance represents an anhydro (Lactone) compound, which adds water in the first stage of hydration.

Similarly, not much knowledge has accrued from examination of the degradation products of wool by standard methods or with special reagents. Gebhard considered that Phenylglycine and Anthranilic acid (o-amino benzoic acid) most nearly resembled wool in behaviour towards Nitrous acid, Acetic anhydride, and dyestuffs. But a more perfect analogy was shown by Anthranoyl anthranilic acid. Under diazotisation, acetylation, and oxidation, and treatment with dyestuffs, the resemblance is so remarkable that the author concludes that either this body or some similar grouping of atoms forms the

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principal part of the wool molecule. (Zeit. f. angew Chem., 1914, p. 297.) On the same general lines, Pauly and Binz concluded that the Tyrosin of wool :—

26. CH. CH. ©H (NH,).

or B-parahydroxy phenylé--amino propionic acid, by virtue of its phenolic character, is the reaction element with diazotising solutions, the same shade being produced as in the fibre. Salmine, Scombrine, and Clupeine—albuminoid bodies con- taining no tyrosine—are not reactive. Silk, containing more tyrosine than wool, is dyed a deeper shade by such solutions. (Zeit. Farb. Text. Ind., 1904.)

The Chemical Combinations of Wool.

The acidity or basicity of wool may be determined by its reactions, and these in general are of a mixed type. L. Vignon determined the heat of reaction of wool with certain common chemical reagents ; working on 100 gm. samples of unbleached wool with normal solutions, he found :—

Potassium Hydrate 24.5 calories.

Sodium Hydrate 24.3 Hydrochloric Acid POD: 5, Sulphuric Acid as

It has always been considered by chemists that liberation or absorption of heat is distinctively a mark of chemical union. It is very desirable that Vignon’s work should be repeated and extended. The process of Chlorination, for example, is noticeably exothermic even in small laboratory tests. The principal technical reactions should be investigated in their thermal aspect; the difficulties of wool chemistry are great enough in themselves to preclude the neglect of any possible lines of investigation. It appears, therefore, that wool substance has both acid and basic properties ; acid, by its carboxyl groups, basic in the amino groups. An extended research by Berold (Inaug. Dissertation, Halle, 1904) treated wool by a large series of chemical compounds, particularly amines, but including acids, bases and neutral salts. 1. Aniline in Acetic, Hydrochloric and Sulphuric acids ; ortho, meta and para chloranilines: dichloranilines : ammonia, ammonium chloride: mono, di and tri ethylamines : benzidine. 2. Hydrochloric, sulphuric, sulphurous, phosphoric, boric, acetic, glycollic, oxalic, malic acids.

3. Picric acid, phenol, sodium chloride, potassium sulphate, etc.

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The results show that wool reacts with acids and bases, but not with neutral salts. The author assumes wool to be :-— /NH,

\ COOH

and concludes that :—

1. Acids and Amines combine chemically with wool; the reaction must be looked upon as additive in a non- homogeneous system. 2. It is not settled whether Bases such as Potassium Hydrate, Tetra-Methyl Ammonium Hydroxide, simply combine (i.e., as salts) with the carboxyl group of the wool or whether they are additive reactions.

The Penetration of Wool by Reagents.

The horny and impervious nature of wool is a great obstacle to its ready reaction with chemical reagents. In the cold, perfect diffusion into the medulla of the wool fibre is a matter of some days; experiments in bleaching wool at ordinary temperatures show commonly a progressive action for a week. When also the varying physical structures of the epidermal scales, the fibrillee, and the medulla are remembered—structure is almost certainly accompanied by differences of chemical composition—then variations in the results of researches are easily accounted for. Behrens (Chem. Zeit., 1903, No. 102), working on the ‘* Behaviour of Fibres to Dyestuffs,’ considers that the inert behaviour of wool towards dyestuffs at a low temperature is due to the impenetrable character of the horny scales on the surface. Thus, crushed wool fibres dyed a bright green at the ordinary temperature when immersed in Malachite Green for two minutes, while an untreated sample took up no colour. Again, wool dyed a dark shade of indigo showed in microscopic transverse sections as follows :—The central or medullary part of the fibre was light blue; the outer part of the cylinder or fibrille blackish blue ; the narrow cuticle of scales was light blue, but much paler than the medulla. This low penetrability of wool—not as a rule properly respected in practical working—necessitates the mechanical actions and heat treatments so characteristic of textile practice. It is with some difficulty that wool under any ordinary condi- tions reaches the turgescent state. This imperviousness bears upon the entire technics of dyeing, bleaching, carbonisation, scouring, etc., and even upon the oiling for wool lubrication. It must not be assumed that treatment of the fibre with a solution of a given concentration means that the internal layers or the medulla have received the proper effect of the full concentration ; in certain cases there is a gradual loss of

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strength as permeation takes place. Some solutions have a tendency to “plump ”’ tissues ; such are most favourable to penetration. Schonbein observed that in filter-paper dipped in aqueous hydrochloric acid, the water ascended higher than the acid; the capillary rise of both weak bases and acids is greater than that of strong solutions.

The Chemical Purification of Wool.

The question “‘ What is pure wool ?”’ involves a secondary inquiry as to the real reactions of wool towards indicators, i.e., its acidity, alkalinity, or amphoteric nature. Obviously, raw wool, containing several per cents. of Potassium Carbonate will react alkaline, or at any rate so will the water extractions from such wool. In the ‘‘ Manual of Dyeing,” p. 40, it is stated that :— ash of a scoured flannel was found to be alkaline. The alkalinity

was due to :— Lime 0.094% calculated as CaO.

Potash and Soda 0.224% A prior paragraph in the same work asserts that :— ‘“The ash of cleaned wool amounts, it is said, to less than 1% of the weight of the material, about three-quarters being soluble in water.” Under these circumstances it is likely that wool will usually be found to be alkaline. Woodmansey, in a paper on “ The Determination of Acid in Woollen Fabric,’’ worked as follows :—

‘‘The pieces of cloth (5 gms. air-dried fabric) were placed in beakers containing the required amount of acid diluted to 300 c.c. allowed to stand overnight, taken out and drained into the solution, which was titrated.

CLOTH, CONTAINING AMOUNT oF N/100 10 GMS. SULPHURIC SOLUTION. TO NEUTRALISE ACID. SOLUTION. 0.05% Alkaline 3.4 c.c. 0.1 do. 2.3 0.15 do. 0.8 0.2 do. 0.2 0.25 Neutral — 0.3 Acid 0.1 ec. N/10 soda.

using four indicators :—Methyl Orange, Methyl Red, Iodide-Iodate, and Congo Red. These results show the wool to be inherently alkaline, a fact previously recorded by Fort, and by Herz and Barraclough in recent publications. The neutralising effect on acids is no doubt due in part to the character of the ash. Cloth similar to the above contained 9.56% of ash, with an alkalinity equivalent to 3 ec.c. N/10 Hydrochloric Acid. Continued washing with water was capable of reducing the alkalinity to some extent. If when cloth is immersed in water the resulting solution be not acid to a sensitive indicator, it may be considered with some justification that the material is non-acid.”

It should be remarked that in matters of this kind, the use of indicators may be misleading. The peculiarities of modern indicators in such work are well understood by the bio-chemists.

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Mr. Fort has conducted, with various collaborators, extended researches into “‘ The Mechanism of the Acid Dye-Bath ”’ and ** The Action of Glauber’s Salt on Wool,’ and related problems. He notes the difficulty of obtaining concordant results by repetition of experiments, that actual absorptions of acid vary with the kind of wool employed, etc. :— ** It has been pointed out in a prior paper that a considerable influence is exerted on the dyeing properties of wool by previous alkali treat- ment, as in scouring. It may in some degree account for the more variable results obtained in these experiments on other classes of wool scoured commercially. Using Botany sliver in similar experi- ments to those recorded, we obtained considerable variation on Een more especially in the absorption figures for sulphuric acid. It is obvious, from the technical literature of past researches, that the material worked upon has not received sufficient consideration, and in many cases is unspecified other than as gms. wool.’”? Some examples in the present aspect from recent work are:—Crossbred yarn, Merino sliver, Botany sliver, Scoured flannel, Cleansed wool, Woollen fabric, Coarse long-stapled crossbred wool, etc. And the preparatory treat- ments, in the rare cases when such are detailed, are as varied. It should be recognised that in certain types of research, it is not well-advised to adopt commercially treated materials, and regard the results accruing as standard. The variations of wool scouring practice are sufficiently well-known to ensure caution in regarding such products as definite or typical ; and the equally well-known retentive properties of wool for certain reagents once applied to it, should teach circumspection. It > is perfectly inadequate to adopt a sample of wool, scoured with alkali and soap, or carbonised and neutralised, washed off in an unknown manner, etc., as a standard substance on which to determine an ash datum, reaction to an indicator, or any general wool constants. If wool is regarded as technical Keratin in the form of fibre, it would appear that any ash-content is a non-essential constituent. The reactions of Keratin, probably an insoluble substance in cold aqueous solution, would have to be deter- mined by the acidity or basicity displayed in its chemical combinations, and the heat of reaction, etc. Commercial wool, outside the carbonising process at any rate, is evidently generally slightly alkaline. But the purely organic matter of wool is more probably amphoteric, i.e., reacts with both acids and bases in the formation of compounds.

A PROPOSED PURIFICATION OF WOOL.

It would be well if there were common agreement among textile chemists that in certain researches a standardised wool substance should be employed. Natural wool, obtained by

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systematic sampling from the fleece, might be purified by a series of extractions carried out at temperatures not exceeding 40°C., say as follows :—

1. Treatments with neutral ether.

2. ee ,, absolute alcohol. a ,, dilute alcohol. 4. es a , distilled water.

All under proper conditions, allowing ample time for penetra- tion to ensure saturation; and conditioned to a definite standard at a particular temperature. The effect of temperature is important ; even pure heated water can affect wool, and chemical reagents at higher tem- peratures are often very active. Under these or similar conditions, some discrepancies between experimental results would certainly disappear.

WOOL GELATINE.

Gardner and Carter (Jour. Soc. Dyers & Colourists, 1898, p. 167) extracted 50 gms. of wool with 1500 c.c. of boiling water for two hours; after filtering and evaporating, they obtained 0.825 gms. of solid residue, which consisted essentially of a horn-like substance, soluble in water, insoluble in alcohol, and containing a mere trace of ash. ‘Thus 100 lbs. of wool would yield 1.65 lb. of ‘ wool-gelatine,’ and if ten lots of wool were boiled in the same liquor, 164 lbs. of the gelatinous matter might be present in the bath. (Not necessarily !— Ep.) These figures alone show that this substance may play an important part in mordanting and dyeing processes, etc. . . . . This substance. is distinctly alkaline, even when prepared from the most carefully cleansed wool, but no ammonia is evolved when its con- centrated solution is heated with caustic soda. The wool-gelatine has only very feeble reducing properties. It decolourises a solution

of Potassium Permanganate on long boiling only, and is very slowly attacked by boiling Chromic

The Colour of Wool.

The question of the intrinsic colour of wool substance is of great technical interest and commercial importance. Wool is extensively used in the undyed condition, natural or bleached ; and undyed wool enters largely into blends and mixtures. Again, the purity and brightness of light shades in dyed goods depend, in the first instance, on a high standard of whiteness in the original wool fibre. These considerations raise the secondary questions of :—(1) What is pure wool ? (2) Is wool a white substance ? The difficulty in answering the first query is the variability of the raw material, and the fact that the different processes of purification affect the fibre, removing certain matters which may possibly belong to the essential constituents, thus upsetting the molecular balance. Even

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simple treatment with hot water will extract some matter from wool; and all stages of decomposition up to complete hydrolysis may be effected by variations of strength of acid or alkali, time of treatment, and temperature. Some of these difficulties are exemplified in the following researches.

Messrs. Herz and Barraclough treated wool first by a Soxhlet extraction, then shaking with water, with benzoline, and then alcohol ; then many times treated with distilled water. On testing with cochineal tincture the wool reacted alkaline. It was now washed in water just acidified by acetic acid for two hours, and again washed with distilled water several times 5. it still reacted alkaline to cochineal. They concluded that wool is normally alkaline. It was subsequently pointed out that cochineal tincture is usually acid.

In a further research (Jour. Soc. Dyers & Cols., 1909, p. 274), these authors extracted scoured wool with distilled water, two boilings on 614 gms. with 8000 c.c. for one hour; these 16 litres were evaporated down to 250 c.c., filtered, and dried out. About three-quarters of 1% of wool-gelatine ’’ was obtained. and a further 0.4% by a repetition of the process. This substance deposits a pale yellow powder from concentrated solutions, and gives the sulphur reaction with sodium plumbite. (N.B.—True gelatine does not give this reaction.) It forms lakes with basic colours, contains at least three components, one precipitable by Barium Hydrate; has an acid reaction to litmus, and is precipitated by tannins, alcohol, lead acetate, or salts of mercury. Gelmo and Suida (Sitzungs Ber. der Kaiserl. Akad. der Wissenschafften, 1906) treated wool with boiling distilled water, dilute hydrochloric acid, ammonia, and dilute sodium carbonate, for 1, 21 and 60 hours respectively ; the samples were then thoroughly washed and dried. Even from the boiling distilled water a smell of Sulphuretted Hydrogen and Ammonia was given off, a yellowish substance was noticed in the condenser, and the wool browned as boiling continued. The Ammonia and Sodium Carbonate solutions also browned the wool; but in acid it remained white, though a quantity of peptone-like organic matter went into solution, 22% in the 60 hours boil, and SH, was freely evolved.

It must be remembered that wool will not suffer without decomposition the drastic treatments that the sister fibre, cotton, undergoes. For comparison, the following scheme of preparatory processes for the purification of surgical cotton is appended :— 1. Washing raw cotton in water. 2. Alkaline boil in 1° Caustic Soda for 12—48 hours at low pressure.

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463 3. Washing. 4. Oxidation in Hypochlorite of lime or soda, about 0.1% Chlorine. 5. Hydro-extraction. 6. Acid treatment, 2°% Sulphuric acid. 7. Washing and hydro-extraction. 8. Second alkaline short boil, 0°25°% Caustic Soda. 9. Washing and hydro-extraction. : 10. Second acid treatment. 11. Prolonged washing. 12. Treatment with Anti-chlor or soap. 13. Final washing. ©

A sterilisation by steam or Formaldehyde may be added. If the production of chemical filtering paper were intended, a boil with Hydrochloric acid or Hydrofluoric acid would follow and the ash contents would be reduced to amounts of tenths or hundredths of 1%. In these cases, the result is a definite chemical entity, viz., CELLULOSE, closely approximating 100% purity. But processes of this type are not applicable to wool substance, and there is consequently no similar per- fection of result. Similar results to the foregoing on the wool fibre in general have been observed by other experimentalists, and are borne out by practical experience. The long boilings of the dye-house, however necessary to the thorough permea- tion by mordants, and fastness of the dyestuffs, are prejudicial to the fibre; the same applies to steaming and the related I processes, crabbing, etc. Compare the height to which a heap of the same wool stands after teasing :—(l) in the white ; (2) in the dyed condition. Even a short treatment on the blowing machine will cause a loss of shade when high whites are in comparison. It may be safely said that for a high standard of whiteness—and on other grounds of handle, strength, etc.—the less exposure of wool to elevated tempera- tures and the better. In a communication by Mons. Martin Battegay to the Societe Industrielle de Mulhouse, on “‘ White Discharge Effects on Wool,” the author says, referring to preliminary processes of singeing, scouring, etc. :— I ** These industrial treatments undoubtedly affect the initial properties of the wool. In this state the dried wool can only be moistened with difficulty, and when immersed at the room temperature in a coloured solution does not absorb any of the colouring matter. It is only by raising the temperature and by the presence of certain salts and acids that the colouring matter leaves the solvent to become fixed on the fibre, . . . . there is every reason for supposing that the term ‘ wool’ is only a collective name for an organic association of many chemical individuals, which according to their origin or their age at the time of shearing, are not necessarily identical. In

this respect, it may be sufficient to recall the morphological com- position of wool; at the centre of the fibre a more or less obliterated

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pith or marrow, different from the epithelial stratum which comes next to it (a mass of fibrille.—Ep.) and this itself differing from the scales or exterior cells enveloping it. Allworden has named a fourth and integral part of the wool fibre as ‘ Elasticum,’ which lodges between the scales and the epithelial cover, and which has been identified as galactose.”’

THE BROWNING OF WOOL.

The experiments quoted above raise also the question of the browning of wool. This is well discussed in papers by Messrs. Fort and Lloyd :— 1. The Development of the Amido Group in Wool. (1914, B11) 2. The Effect of Certain Agencies on the Colour and Dyeing Properties of Wool and Silk. (Fort, 1916, p. 184.) (Jour. of Soc. Dyers & Colrts.) In general it may be said that all alkalies produce in wool a yellowing or browning effect ; the hydrates of potash, soda, ammonia, and even the alkaline earths, lime, baryta, strontia and magnesium ; and the carbonates of these elements. And also generally, dilute acids have a whitening action, producing in effect a partial bleach. This latter is said to be due to salt formation by the acids and wool, a chemical reaction occurring and being accompanied by thermal changes (Vignon). An immediate technical inference from these broad rules applies to the practice in certain branches of the industry, of bleaching wool in the fibre state when such wool has to pass through all the stages of manufacture and particularly the scouring process, with its usual alkalinity. the custom, for example, in the hosiery industry, and in order to secure the maximum brightness and contrast in black and whites—e.g., Scotch woollens—to give the wool a bleach, often an expensive peroxide bleach, in the unspun state. It may be doubted whether, in the final fabric, this process has any ultimate utility. The wool is oiled for the stages of yarn production, and the woven pieces are milled and scoured under alkaline conditions. It is probable that this annuls entirely the good effects of the earlier bleaching, the creaming effect of the alkali letting the shade produced by bleaching down by several per cents. Mr. Fort points out that browning of wool may result from exposure, dry heating, steaming, boiling with water, action of alkalies and strong acids, to which may be added chlorination for shrinking purposes. It is asserted that this browning is due to the development of free amido groups in the wool, but it is possible that all browning is not of the same origin as regards the wool. In Sulphur bleaching, if Sulphurous acid gas is dissolved in alcohol—in which it is much more soluble than in water—and wool is immersed in this solution, in some cases at least a pure lemon-yellow colour results. Here again

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we. are lacking in an intimate knowledge of the chemistry of the wool molecule. The practical outcome of these results of research is in the direction of avoiding excess in heat treatment, boiling or crabbing, mordanting, and dyeing, hot pressing, calendering, decatising and steaming, strong solutions of alkalies, etc. It must be remembered that the wool originally grew at the body temperature of the sheep, about 98-99°F. (37°C.) ; the more the processes of the wool industry can approximate to this natural standard and the better the artificial result. It will be seen later that this temperature is an optimum for milling (Harrison) ; it is apparently an optimum for scouring also. Returning to the question of the intrinsic Colour of Wool, it has been shown that when attempts are made to prepare wool in a chemically standard form, some variability remains. Neglecting this factor, however, the other element presents itself, viz., ‘“ What is the standard of Here there is a nearer approach to absolute conditions. For purposes of colour research there are recognised certain chemical substances, viz., Zinc Oxide, Calcium Sulphate, Magnesia, etc., capable of preparation in a high degree of purity, and forming reproducible standards of OPTICAL WHITE. When the textile fabrics are judged from this standpoint, great differences reveal themselves. Cotton in its highest state of technical perfection, e.g., surgical cotton, is probably the most perfect textile white produced ; pure cellulose, in the form of labora- tory filtering paper, is a useful and handy standard of reference for the works chemist. Compared with well-bleached highest quality cottons, any wool fabric is markedly inferior, no matter to what bleaching process it may have been subjected ; the same may be said of silk. If attempts are made by many repetitions of the bleaching process to secure a very high white on wool, the fibre becomes tendered and ‘“‘ rotten ’’; as also does silk. The chemical changes corresponding to this are unknown, as indeed are those of bleaching animal fibres in general. It would appear then that ordinary industrial wool, however highly selected, scoured and bleached, IS NOT AN AB- SOLUTELY WHITE SUBSTANCE or fibre; at any rate in so high a degree as cotton. At the same time, it is probable that the bulk of fabrics involving either white wool alone, or admixture of white wool with other shades for contrast or design effects, etc., are turned out in less technical perfection than need be. Radical improvements are possible at the piece scouring end of most manufactories ; lack of lustre, loss of brightness and effective contrast result from neglect at this critical stage, and much of the possible beauty of the finished fabric is never attained. GG

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466 PROTEIN CHEMISTRY AND WOOL.

The special chemistry of the wool substance shows little progress, but advances are rapidly being made in the general chemistry of the proteins. Loeb (The Proteins and Colloid Chemistry), states that ‘‘ The behaviour of the proteins there- fore contradicts the idea that the chemistry of colloids differs from the chemistry of crystalloids.’’ Proteins exist in three states defined by their hydrogen ion concentration :—

1. As non-ionogenic or iso—electric protein.

2. As metal proteinate (e.g., sodium or calcium proteinate). 3. As protein acid salts (protein chloride or protein sulphate,

etc.). Using gelatin as an illustration, there is a definite hydrogen ion concentration, viz., P, = 4.7, at which it practically

forms no combinations with either anion or cation of an electrolyte. At greater P,, values it forms metal proteinates and at lesser the acid salts. It follows therefore that the concentration of hydrogen ions as well as that of protein, must be known in order to characterise the substance. The subjoined extract from Loeb has a direct bearing upon the vexed question of the acidity or alkalinity of wool :—

When we add an acid, e.g. HCl, to iso—electric gelatin (or any other iso—electric protein), an equilibrium is established between free HCl, protein chloride, and non—ionogenic or iso—electric protein. When we add an alkali an equilibrium is established between metal proteinate, nun—ionogenic or iso—electric protein and the hydrogen ion concentration. The hydrogen ion concentration determines the quantity of protein salt formed.” It can be shown by experiment that all acids whose anion combines as a monovalent ion raise the osmotic pressure, viscosity and swelling of protein about twice as much as those whose anion combines as a bivalent for the same P,,. Martin Fischer (Soaps and Proteins) has emphasised the marked resemblance in the phenomena of hydration of the soaps and proteins. There are chemical analogies, e.g., if the formula of a fatty acid be written :—

X—COOH, then that of an amino-fatty acid is ae

NH, To produce a soap some base is substituted for the hydrogen of the first formula, and a similar substitution can be effected in the second case. Thus as there are potassium, sodium, calcium and iron soaps, there can be produced potassium, sodium, calcium and iron proteinates. ‘““ Every new soap and every new soap-like compound thus formed has solubility characteristics in water and for water different from those of the original fatty acid or the original amino fatty acid (protein) from which it was produced.”

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The proteins comprise types :—

1. Insoluble in water, such as egg-globulin. 2. Soluble in water, such as gelatin.

This distinction is not absolute, as at the isoelectric point gelatin is insoluble and not very hydratable like globulin, which is a relatively poor solvent for water (92°) and does not dissolve. When, however, traces of acid, alkali, or salts are present, the degree of hydration is altered, often excessively. (Compare the interesting cases of sulphuric acid on wool, in acid milling, caustic soda, etc.).

It is necessary to consider :—

1. The quantitative relationships of the water content of protein systems to the remaining material in them. 2. The chemical conversion of “ neutral” (? isoelectric) compounds into basic or acidic derivatives. 3. The alterations in solubility and hydration capacity accompanying such changes. 4. The types of systems produced, whether all hydrated colloid, all solution in water, or subdivisions of one in the other. ‘5. Changes in viscosity incident to emulsification in suspensions of one phase in the other.

The phenomenon of “ swelling,’’ says Martin Fischer, is a change whereby the protein enters into combination with more of the solvent (water) in the direction of greater solubility of the solvent in the protein ; while solution is best conceived as a change in the direction of greater solubility (i.e., a greater degree of dispersion) of the colloid in the solvent. If a 10% solution of gelatin is precipitated at 30°C. by the addition of a neutral salt (e.g., sodium sulphate), and allowed to stand for some hours at the same temperature, the gelatin is found in both layers; the uppermost liquid one contains but little gelatin, the lower layer is correspondingly rich in gelatin. Similar phenomena are seen in Casein.

THE GELATIN ANALOGY.

In view of the frequent and often instructive parallels drawn between the behaviour of KERATIN (wool substance) and Gelatin, it may be useful to summarise the relevant matter in this connection. The resemblance, as far as it goes, is that of two members of a great class of organic substances, the Pro- teins, and gelatin being a soluble protein is not perhaps the nearest relation ; still there are remarkable points of likeness. Both keratin and gelatin are amphoteric, i.e., they exhibit both acidic and basic properties. In gelatin, this is definitely connected with the hydrogen ion concentration and the substance is neutral at one concentration :—The Iso-electric point, Py = 4.7.

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For values greater than this it behaves as an acid and combines with the cations of organic and inorganic electrolytes ; for values less than 4.7 it is a base and combines with anions. ‘The viscosity and swelling are at a minimum at this point ; acid and alkali gelatinates are more strongly hydrated than neutral gelatin. Inasmuch as wool does not dissolve to a solution—at all events in ordinary conditions of temperature and pressure— the analogy with gelatin cannot hold good all along the line. It does not appear that an isoelectric point for wool has been determined or its existence settled. But the acidic and basic characters are abundantly demonstrated, both experimentally and in technical applications, e.g., dyeing. A basic dyestuff is retained by gelatin when it is functioning as an acid, that is on the alkaline side of the isoelectric point, where gelatin anions are present ; on the acid side and at the point itself the dye is readily removed by washing. The basic dye, Neutral Red, behaves in this way. Similarly, acid dyestuffs like Acid Fuchsin combine with gelatin only when the P, is less than 4.7. As gelatin has none of the sulphur containing amino acid Cystin, its solutions fail to give the glyoxylic, Millon’s and sulphur colour tests for proteins; and give only a slight xanthoproteic test. These are marked distinctions from keratin, the chemical basis of wool substance. The swelling properties have not yet received thorough investigation, but it is known that acid and alkali modify these. Concentrated solutions of certain salts inhibit the swelling of gelatin, and in addition it suffers special changes, being permanently hardened by salts of aluminium, chromium, and iron. Certain salts prevent the bleeding of colour from wool, and the particular compounds above act in a similar way on wool. Formaldehyde hardens gelatin and wool also. The absorption of liquid water by gelatin is accompanied by evolution of heat, a well-known technical phenomenon in the crabbing, dewing, etc., of wool materials. But there is con- siderable evolution of heat when animal charcoal is wetted with hydrocarbon oils, in which case it is difficult to assume chemical action. When actual solution of gelatin follows, there is an absorption of heat. An interesting colour reaction on wool was noted in 1909 by Meunier, who showed that neutral wool treated with quinone vapour or solution became purple red. It has since been -shown that the reaction depends on the presence of moisture. E. R. Trotman (Jour. Soc. Dyers & Cols., Mar., 1924), in a paper on “‘ The Relation between the Nitrogen of Wool and the Affinity for Acid and Basic Dyes,” summarises the research work done on the amino groups of wool. He repeated the

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de-amination of wool performed by Benz and Farrell, noting the brown colour thus produced, and concludes, in opposition to Fort and Lloyd, that the primary amino groups of wool play no part in the acid dyeing of this fibre.

The Physical Properties of Wool.

It has been common—and has hitherto been thought sufficient—in the scanty technical literature of the wool industries, to make superficial statements concerning the properties of the wool fibre in the physical aspect. Wool is said to be “ elastic,’’ hygroscopic, plastic in moist heat, etc., and but little strict inquiry into the extent of these properties has been made. In particular, few or no exact laws or formule have been determined, and the amount of experimental research has been small. The relations of water and wool are in the scientific aspect very complex, and on the technical and commercial sides, of extreme importance; they are therefore taken in a separate section. The mechanical properties of the fibre are intimately concerned in all the spinning, weaving and finishing stages, and it is consequently desirable to discuss these in their scientific aspect. Wool has already been noted as a colloid substance, and like all colloids shows special mechanical properties. Being fibrous, it has the particular qualities under external stresses of filaments in general. Wool cannot be produced in large homogeneous masses. The wool fibre is not in itself a simple structure, and its three principal layers—scales, cortex and fibrille—are probably not chemically identical. A complete physical description of the fibre includes data such as :—

1. Average lengths and diameters for different qualities. 2. Mass and volume ; and specific gravity. 3. Special characters such as:—Number of curls and number of scales per unit length. There will also be, in the broader sense of Physics, the mechanical properties such as Extensibility, Elasticity, Plasticity, etc.

Some few of the older data regarding the length, diameter, etc., of certain wools are given in the chapter on Milling, and for the purpose intended may be retained. But accurate measures of these quantities are still wanted. There is enormous variation between individual fibres in a material like wool, where a pound weight may contain millions of fibres. No figures have any real meaning unless they have been derived by proper statistical methods from a very large number of single measurements. If from this aggregate the groups within similar narrow limits are sorted, a frequency diagram can be prepared and the predominant groupings

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distinguished. The amount of variation from the mean can be observed, and the accuracy of the individual measurements assessed. A result may then be deduced which is probably standard for the material.

A table by Holden gives the following relations for wool quality and thickness :—

QUALITY DIAMETER QUALITY DIAMETER NUMBER. IN M.M. NUMBER. IN M.M. 80s 0.0201 548 0.0294 70 19 50 320 64 45 48 343 60 56 46 366 58 66 40 420 56 78 36 452

The staple lengths vary greatly, being longer in the coarser qualities, which approximate to about 8 inches, medium wools about 4, fine wools 3 inches ; the waves or crimps for the same wools are about 14, 9, and 20 per inch.

Prof. Eber Midgley has given a table of lengths of fibres in

various wool qualities :—

QUALITY VARIATION IN LENGTH. NUMBER. EXTREME LONG. EXTREME SHORT 28s 15 24 ins. 36 124 2 44 11 2 50 9 13 60 5 14 70 43 13 80 43 14 90 43 14

The specific gravity is about 1.30. _ Barratt has given an interesting table of the breaking strengths and extensions for the usual textile materials, based on single fibres :—

BREAKING EXTENSION KIND OF FIBRE. STRENGTH. % OF ORIGINAL. Cotton (scoured 7.2 7.4 Cotton (mercerised) a7 12.2 Wool (merino top) 7.85 39.0 Silk 4.01 $8.7 Viscose 10.8 14.5 Linen 19.5 5.1

From which it appears that wool is five times as extensible ‘as cotton, and twice as much as natural silk.

DEFINITIONS.

It is very necessary that in the investigation of the mechanical properties of textile fibres the terms employed should not be used in senses other than those accepted in engineering circles or in the standard mathematical works on the properties of materials. A flagrant case in textile circles is the misuse of

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the terms “ elastic, elasticity,” for elongation or extension. It will be useful to define exactly some of the commoner terms used in mechanical testing.

STRESS is the force applied to a body, viewed not merely

as resulting in motion, but producing: some kind of deformation.

A TENSION is a stretching force reckoned per unit length.

A PRESSURE causes contraction, and is calculated as force per unit area.

STRAIN is the deformation resulting from the application of astress. A tension applied, as during spinning, produces an elongation or extension in the fibre or yarn ; this is the quantity so frequently and wrongly called “ elasticity ’’ in textile circles.

ELASTICITY is the property of recovery from strain when the applied stress is removed, e.g., the shortening and un- twisting of fibres and yarns are due to the elastic nature of the wool substance. A truly plastic substance when stressed retains its deformation completely, and is therefore perfectly inelastic. Wool, when moistened and hot, as in roll boiling, dyeing, blowing, etc., is plastic ; it has lost the quality of RIGIDITY. Flexible or pliable substances easily bend under stress, i.e., they are not brittle. The Elastic behaviour of a material in general depends on two properties :— 1. Incompressibility ; resistance to change of volume. 2. Rigidity ; resistance to change of shape.

The rigidity is mainly concerned in the time-effects or permanent sets given to wool in certain operations, e.g., crabbing, pressing, etc. In fact, PLASTICITY is the property converse to rigidity, and enables the material to take permanent set.

Elasticity of Wool.

The substance of wool possesses both elasticity and plasticity, and these are very much dependent on its content of moisture and temperature. Under mechanical stresses the behaviour of the fibre is a composite result of the elastic and plastic pro- perties, and it is important to investigate a typical case, e.g., a tensile test on a single fibre. In all the textile fibres there is a concurrence of large semi-permanent strains with a purely elastic strain, and even under constant conditions of moisture and temperature, the presence of the plastic element is revealed. The rate of application of the stress has to be governed by this viscous factor. Under these circumstances, it is convenient to take LOAD-EXTENSION tests by autographic instruments ;

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the fibre, as the load is applied, is made to draw its own stress- strain diagram. Numerous forms of apparatus have been devised for this purpose, ordinary yarn testing devices modified to gain sensitiveness, pendulum balances, spring and lever mechanisms, etc., being employed. It is found that generally yarns with considerable twist give similar results to single fibres, and even fabrics reveal the main factors in their diagrams.

A typical diagram taken from a recent work is given herewith :—

3 2 Q A wl B be x ad D ¢ Fic. 135, Fig. 136,

In the case of wool, the investigations hitherto conducted have been mainly confined to the longitudinal elasticity, and the following summary of Shorter’s experiments is taken from his paper “The Physical Properties of Textile Fibres,’ etc. (Faraday Trans., 1924.) Referring to the diagram, Fig. 135, on applying tension the curve starts, out in the direction OK but with increasing rate of extension, assumes the path OA. On unloading, there is no instantaneous recovery to the initial state as in materials like glass, steel, etc. Instead, the portion ABC is traversed, leaving a residual strain OC at zero load. A new application of the load produces the graph CDE. It is shown in the paper that the peculiarities of this stress- strain diagram may be illustrated by a dynamical model such as Fig. 136. This system consists of two perfectly elastic elements in series, the springs S and §8,; these are attached to a piston working in a viscous liquid, and the piston is pierced by a fine capillary channel. While the first elastic spring S is un- restricted, the second, S,, is impeded. The model illustrates the delay in taking up full elongation proper to a given load,

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the residual extension when the load is removed, the slow recovery on removal of external stress, etc. The study of the autographic tests and the dynamical analogies has led to a theory of the colloid nature of wool by Shorter, which assumes the presence in the fibre of free elastic elements, impeded elements, and viscous elements ; the fibre ““ consists of an elastic framework, the interstices of which contain a viscous fluid . . . . the elastic portion is very resistent and the viscous portion very susceptible to the action of Some special features of the tests are discussed in

oP. AUTO STRESS - STRAIN

LOAD

Fiq. 137.

this connection and the theory is applied to the explanation of certain points in shrinking and other finishing operations. The original papers should be consulted and also the biblio- graphies appended thereto. In the case of steel, the first portion of the curve OP com- prises all the limits of the preceding case. The relation between load and extension is linear, i.e., the extension is directly proportional to the load, which is Hooke’s Law for elastic bodies. “‘‘ As is the stress, so is the strain’’; P is the elastic limit, after which the steel yields, the material beginning to creep at Q, ultimately breaking at R. But in colloid substances generally and the textile fibres in particular, some viscous or plastic element is present from the beginning. The early stage is not really linear, and the removal

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of the stress reveals the existence of residual strain ; recovery is not immediate and complete, as in steel. A perfectly elastic substance within its limits of elasticity gives a straight line trace in which load-line and unload-line are coincident ; a perfectly plastic body on unloading remains in its new configuration, showing no tendency to return to the original state, but retaining all the strain undiminished. Wool is a composite substance, having both plastic and elastic properties. The former cause a delay or time-lag in taking up the strain proper to the applied stress. Further, if the wool yarn or fibre is allowed to rest, it recovers by a slow creep from the strained condition (in whole or in part), providing that the time is sufficient and that the strain has not been excessive. Finally, if the fibre possesses initial strain and is subjected to a certain stress, the curve of stress-strain will vary according to the mode of approach, i.e., it shows HYSTERKSIS. If sufficient time is allowed, the wool substance regains its pristine condition very closely, and to this extent is an elastic substance. In the case of a LOAD-STRETCH test, the law will probably be of the form :— 1, =1, [ec + a (1 —e —*)], where 1, = length at any time “t.” 1, = original length. a, b, c = constants. The two factors in this expression represent the elastic and plastic elements of the case, the rapid free extension and the slower impeded extension. In some tests by Shorter, a fibre on a total extension of 13.5 m.m. showed a residual strain after 16 minutes rest of only 1 m.m. In another case, a fibre 22 ems. long extended 4.2 cms.; eighteen days afterwards the extension was I centimetre only. One of the practical results of the autographic testing is to determine more exactly the relations between the strength of yarns and that of the individual fibres of which they are composed. It has long been a matter of discussion among practical men whether yarn bears stress individually or collectively ; if the former, single tests on fibres are correct ; if the latter, the hank test is indicated. It was formerly thought that the yarn strength depended only in a minor degree on the fibre strength. Observers estimated that one- fifth to one-quarter of the fibre strength was realised in the yarn. Later measurements have shown that this figure is perhaps too low ; it can be nearer two-thirds. It has further been shown in tests on fabrics, e.g., aeroplane cloth, that the stress-strain cycle is similar in nature to those of fibres and yarns in respect of the plastic effects being superadded to those of ordinary elasticity ; or, viewed in the other aspect, regarding the great importance of the time-factor. The recovery from

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strain is greater for fibres like wool than in cotton; it is a measure of the true “‘ tensile elasticity,’ as distinguished from mere extensibility. In wool, there appears to be a large rapid recovery followed by a second stage smaller and slower. Barratt gives a comparative table :—

FIBRE. RECOVERY FROM STRAIN. Cotton, scoured 0.28 Cotton, mercerised 0.34 Wool, merino top 1.33 Silk, natural 0.87 Linen 0.11

PLASTICITY OF WOOL FIBRE.

The apparently imperfect elasticity of the wool fibre, 1.e., its partial or delayed recovery from strain, is at once the source of possibilities of manipulation and difficulties of operation. It arises in all stages from the twisting of fibres into yarns by the spinner to the processes of the cloth finisher. It is enormously dependent on the moisture content and on the temperature and is indeed the fundamental basis of the textile arts. A really plastic substance suffers a change of shape without change of volume, i.e., the mechanical property involved is RIGIDITY. Investigations on the. elastic properties of materials usually measure the rigidity by torsional experiments on filaments of the substances, either by oscillation methods, using the torsional pendulum, or by applying statical torsional couples, thus producing pure “shear ”’ in the material. Some tests by Peirce, in which fibres and yarns of cotton, wool, silk, etc., were subjected to constant twist and the decay in the torsional resisting couple then observed are illustrative of the nature of the results in textile cases. (Jour. Text. Inst., Nov., 1923.) In this kind of strain the plastic properties of im- perfectly elastic materials are well revealed, and the experi- mental conditions make comparisons easy. In these tests the fibre was fixed to a torsion head by which the required twist is applied and the couple is measured by a magnet suspended from the fibre in a known magnetic field. After twisting up the fibre, the couple is observed continuously until it falls to a practically constant value, and a curve of couple against time This is expressed by an equation of two terms :— 1. A final constant value expressing the elastic effect persisting indefinitely. 2. A portion disappearing with the time. There results a formula with three constants :— C = the initial static couple. c = the percentage of C persisting under strains of long duration. b = a time coefficient of rate of loss of plastic strain.

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The law of decrease of torsional resistance with time is :— C, = c + ae —?, Pierce states that this appears to be a general law of decay of strain for plastic solids. The results correspond with the known characteristics of the textile fibres. Silk is remarkable for its resilience, it being exceedingly free from creasing after being crushed up. Wool is somewhat more plastic, but is still spongy. Cotton is more imperfectly elastic than either.

TENSILE STRENGTH AND REGAIN.

Wool is generally stronger at low contents of moisture, but the elongations under tension are greater at the higher values. Woodmansey gives the table below for some material dried out at 100°C. and then placed in a dessicator :—

AVERAGE AVERAGE STRENGTH ELONGATION MOISTURE oF 5 WARP BEFORE CONTENT. STRIPS 3INS. RUPTURE. Ibs. ins. % Out of Dessicator 188.4 1.225 Dry. After 5 minutes 185.8 1.525 3.0 After 15 minutes 172.4 1.800 6.5 After 30 minutes 161.0 1.875 7.08 After 60 minutes 158.4 2.150 a. 7 The cloth was then wetted and allowed to dry in the air. AVERAGE AVERAGE STRENGTH ELONGATION MOISTURE OF 5 WARP BEFORE CONTENT. STRIPS 3INS. RUPTURE. Ibs. ins. % Before treatment 160 2.26 10.04 Just after wetting 130.7 4.53 53.0 Damp 123.6 4.46 33.0 Air-dry 156.3 2.67 10.54

WET AND DRY RAISING.

An important practical application of the change in elasticity with content of moisture in wool occurs in the raising process, which may be carried out on the fibre in two distinct states. In the dry state, i.e., with a normal condition, the raising is of a more superficial character and the pile of fibre is rougher and looser. Wet raising is practised on the fabric in all degrees from mere dampness to limp wetness, and there may be also stages of “dry beating ’’—alternations of steaming and raising—to get up the fibres and produce a definite “lie ” in the finish. To get this effect, as in beaver cloths, it is essential to bring the wool into a plastic state, which is obtained by the dewing or steaming. If raising follows the scouring process directly, the greatest softness of pile results, the ‘‘ velvet ”’

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finish. The different effects of dry and wet raising have been explained by assumed electrical effects in the former case, bringing in the familiar repulsion of similar electrical states. This supposition is hardly adequate and is forced ; it could not, for example, explain equally the differences between damp and wet raising. The known relations of the elastic and turgescent properties are sufficient.

THE RELATIONS OF WOOL AND HEAT.

In the practical aspect, the relations of the wool substance and heat are always complicated by the third factor of moisture and but little direct thermal connection has been worked upon. Dietz has determined the specific heats of the principal textile fibres :—

Raw Silk 0.331 Artificial Silk 0.324 Boiled off Silk 0.331 Linen 0.321 Worsted Yarn 0.326 Cotton 0.319

The HEAT OF SORPTION by wool has received thermo- dynamical treatment by Shorter. Trouton had deduced that if the latent heat of evaporation of water from the material is equal to the latent heat of water in bulk, then the moisture content of the material depends only on the relative humidity of the environment and not upon the temperature. But textile materials develop considerable heat when absorption of water occurs, and Schloesing has proved experimentally that the regain does depend on the temperature. Experimental data on cotton, by Barratt and Lewis, confirm the values calculated from theory. Incidentally, the laws of regain by Hartshorne (See chapter on Wool and Moisture) may be checked as regards the temperature factor by these theoretical considerations ; as might be expected on other grounds, they are not borne out. (Shorter; The Thermodynamics Water Absorption by Textile Materials). There will probably be considerable theoretical enue to be attached to the work on the thermodynamics of water absorption. The values at low regains of the heat of absorp- tion are surprising large, and in the case of wool comparable with the latent heat of evaporation. Thus in the early part of the curve, i.e., the portion usually ascribed to the so-called ‘‘ chemical ’’ water, this high value of the absorption heat becomes very significant. The process of absorption in this stage must be differentiated from the diffusion characteristic of the later absorption. There are here molecular as distinct from molar phenomena in the subsequent stages. The initial volume contraction accompanying sorption is also large at the lower regains. (Cf. J. R. Katz, Die Gesetz der Quelling. Kolloid Chemische Beihefte.) It must be noted

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that the “ heat of wetting ”’ or heat of soaking is to be distin- guished from the general heat of absorption ; the former is of I the order in wool of zero calories per gram at 34% regain and 12.9 at 7% regain. But the heat of absorption reaches 110- 120 calories per gram of water absorbed for regains in the neighbourhood of 8-11%. Shorter sums up the conclusions as follows :—‘‘ When the fibre is dry the attraction for water molecules is very great, so that we get a large heat of absorption. As the water content increases the intensity of the attraction and consequently the heat of absorption diminish. AS saturation approaches, the water absorption approximates more and more to the mere coarse grained soaking up of water such as occurs with a sponge, so that the heat of absorption approaches zero.”’ Some new work respecting the action of Chlorine on wool is contained in a paper by Meunier and Latreille on ‘‘ The Industrial Chlorination of Wool ” (Jour. Chim. et Ind., 1924). After discussing the older method, using chloride of lime acidified by hydrochloric acid, the authors point out the difficulty of obtaining uniform results ; in excess, there is a loss of weight and erosion of the epithelial scales, with a decided susceptibility to wetting and a gummy handle in alkaline washing solutions. It is confirmed that there is some elimina- tion of sulphur from the wool as sulphur chloride. They state that there is formation of chloramines of the type R. CO. NCI. R from the —CO. NH— groups of the protein molecule. These chloramines can be eliminated by treatment with sodium bisulphite solution. It has been known in the works where chlorination is practised for non-shrinking that the sulphur bleach following on chlorination produced sulphuric acid and largely removed the browning action of the chlorine. The general effect in ordinary treatments with chlorine is that of oxidation of the protein matter. Chlorination reduces the surface tension of wool, causing it to become more easily wetted, but it deprives the fibre of some of its power of swelling, an observation of importance in connection with chlorinated wool and milling. Similar actions are observed in gelatin and on the human skin. In “dry” chlorinating, the oxidising effect noted above in solutions is replaced by a real absorption and chemical combination with the fibre.

STRUCTURE OF THE WOOL FIBRE.

Nothusius, in 1894, gave a method of breaking up the wool fibre by long treatment with dilute ammonia ; the fibrillee were about one micron in diameter, generally parallel with the long axis of the fibre.

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For the investigation of colloid substances, such as the textile fibres, it is useful to consider strains of three types :—

a Elastic Strains, which are proportional strictly to the applied stress and have no latency, e.g., small strains in metals. II. Ductile Strains, which exhibit a semi-viscous flow continuing with the time; these are not reversible, and lead to thinning out and final rupture of the

material. IIf. Epibolic Strains, which show the effect of “‘ after- working ’’; the strain increases with the time, but

at a decreasing rate, and attains a final equilibrium ; after the stress is removed the strain finally dis- appears or decreases to a small value, e.g., wool fibres. In some researches on these, two to three days have been allowed to elapse at one loading, there being an immediate extension, followed by a long slow sweep to equilibrium value. Speakman has shown that the extension of wool fibres at breaking point (maintained under particular conditions of saturated air, etc.) is a constant at about 70%.

The micrometric method ‘of estimating wool fineness, and hence wool “ quality,’ has been tested at the University, Leeds, and the following table has been published by Prof. A. Barker. It is pointed out that a fleece will usually contain seven or eight qualities, and formula are derived connecting the fibre diameter and the quality numbev.

DIAMETER DIAMETER IN BRADFORD ~ RECIPROCAL 1/100M.m. (QUALITY NUMBER. BY FORMULA. 54.04 36s 470 39.19 44. 648 36.50 46 696 28.25 54 899 25.23 58 1007 23.86 60 1064 18.66 70 1361 15.06 80 1686 10.54 100 2408

The conclusion is drawn that under normal conditions the work of the well trained wool classer or wool sorter is trust- worthy, and that, broadly speaking, micro-metrical sorting will not be markedly better, and if not carefully undertaken may be worse. A method of estimating fineness in fibres involves the use of the micro balance, various forms of which are available and may be employed_in work on the physics of the textile

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Thus, if the total length of fibre in a small sample is measured and the sample weighed, a datum is obtained, viz., the number of centimetres to a milligram which is characteristic of the wool quality ; that is, it is a form of length per unit weight estimation. The following are figures given by Barker for various wools :— :

Lincoln 36s 64.4 cms./mgm. 3/1 bred 44s 89.9 3/4 bred 46s 120.4 1/4 bred 54s 147.5 Comeback 58s. 187.0 Comeback 60s 208 Merino 70s 294 .3 Merino 80s 318

THE SPECIFIC GRAVITY OF WOOL.

This important datum has received much attention in recent years, nearly all observers using the method of the specific gravity bottle with more or less refinement of experiment. In the “‘ Journal of the Textile Institute,’ Jan., 1926, King has given some data regarding the swelling and sorption of wool in various media. The sorptive effect is a minimum in Benzene, Toluene, Nitrobenzene, and in Olive Oil and Oleic Acid. There is good agreement in the experimental determinations of the density of wool, which may be taken as 1.30. In water, the soaking regain, i.e., the regain on immersion, and the ordinary regain are the same and amount to about 33% at 25°C. This conclusion may be compared with the discussion of this im- portant quantity in the chapter on “‘ Humidity ” in this book and the paragraph entitled of Sorption (The Wet Processes of the Wool Industries, 1921). The apparent density corresponding to this state of sorption is 1.27. There is a regain of wool in other liquids :—

Methyl Alcohol 26.3% Ethyl Alcohol 21.3% Benzene less than 0.5%

RECENT CHEMISTRY OF WOOL.

The primary properties of wool substance (Keratin) have been recently receiving attention by Trotman, Paddon and, at the Leeds University, by Speakman, with the particular aspect of acid absorption and the chemical theory of dyeing in view. Reference may be made to two full papers in the Journal of the Society of Dyers and Colourists for Dec., 1924, and May, 1925, on “ The Behaviour of Wool as an Amphoteric Colloid.’’ In the former, the long controversy regarding the absorption of acid by wool is discussed, the experimental results of Fort and Lloyd, Georgevics, and Dietl are compared, and it is

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shown that this absorption follows the ordinary laws of chemical combination ; the conclusion being that when the hydrogen ion concentration of the acid is taken into account, all these results are capable of rational interpretation. On the known amphoteric character of wool colloid and with Loeb’s results of protein relation to H ion concentration in view, a restatement of the chemical theory of wool reactions—par- ticularly in respect of dyeing phenomena—is made.

: Pi ye : Lt :

0 2 3 4 5 6 7 8 Fre. 13s.

wo

Fig. 139.

Iso-ELECTRICc PoINT or Woot.

Speakman has made a determination of the Iso-Electric Point of wool. Samples of purified wool were immersed in Potassium Ferrocyanide solutions brought to definite degrees of acidity by known amounts of Hydrochloric Acid ; after 24 hours, the samples were removed, well washed and put into Ferric Chloride solution. Where combination of wool and Ferrocyanide ions had occurred, the wool was coloured blue. The H ion concentrations were measured by the hydrogen electrode. The combination begins at pH = 4.8, and with decrease of pH there is increase of the amount of Prussian

HH

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Blue formed. The iso-electric point for wool is therefore definite and is in the neighbourhood of pH = 4.8. (Cf. the paragraph in this chapter on the Gelatin Analogy.) Rey and Meunier have also determined (Compt.rend. 1927) the iso-electric points of wool and silk. Two gram samples were immersed in 100 c.c. of buffer solutions varying from pH = 1.0 to 10.0, until equilibrium was attained, i.e., for about 40 hours. The pH of each solution was then found and the imbibition of the fibres obtained by weighing the centri- fuged samples. By plotting the pH values against the percentage imbibition, curves, showing a sharp minimum at 3.6 to 3.8 were obtained for wool (for silk, a flatter minimum at 4.2). An important contribution to pure chemistry in the proteins was made about eight years ago» by the Russian chemist, Zelinsky, who showed that on careful hydrolysis of the protein derived from goose feathers nearly 80% of 1:4 diketo piperazines are obtained and not the amino acids, as was to be expected from Emil Fischer’s general formula. (See earlier sections of this chapter.) Zelinsky therefore concluded that this protein is not a chain compound—as in formula I below—but rather a mixture of ring compounds of the general formula IT :—

(I). ee ee ee

NH, R COOH (It), / NH—CO\% R—CH CH—R \ CO—NH 7 Abderhalden confirmed Zelinsky’s results and has been followed by Jaitchnikoff, it is stated, with the result “* that the Fischer formula now becomes obsolete.”

EFFECT OF HUMIDITY ON FABRICS.

In a research mainly concerned with the effect of humidity on the strength of fabrics, Parker and Jackman (Jour. Soc. Chem. Ind., May, 1925) confirm the wellknown result that cotton increases in strength with humidity, while wool is weakened ; these results were obtained, not by the usual tensile tests, but by the Mullen bursting tester. - Effects of Different Treatments on the Strength of Wool. Humidified at 70 R.H., 70°F. 38 Ibs./sq. in. 100% Wetted (tested at once) 21 Wet for 24 hours — =

Boiled in distilled water, 1 hour 19 3 50% 0.3% Sod. Oleate, 60°F ., 48 hours 21 as 55% 1.0% Sod. Oleate, 140°F., 1- hour 18 47% 1.0% Sod. Oleate, boiling, 1 hour 10 26%

1.0% Sod. Carbonate, at boiling, 1 hour 13%

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Similar phenomena are shown by silk to a less degree, and celanese and viscose greatly. Much attention and effort have been exerted in recent years to secure unanimity in various countries in the classification and nomenclature of the different qualities of the wool fibre. A chart of wool qualities, by the courtesy of Mr. G. T. Willingmyre, of the American Board of Agriculture, U.S., is given later. A novel method of attacking the problem of wool quality is seen in the system of Dr. Heuseler, now known as the Munich method. It seeks to replace the existing classification and valuation through the senses of sight and touch by a purely objective test. Projected pictures of wool samples, yarns, or portions of fleeces are thrown upon a screen of parchment, ruled into millimetre squares. An _ operator, behind this screen, may take measurements and make com- parison with standard pictures of the type. This system, as contrasted with certain micrometric methods practised in recent work, is essentially a mass examination. In particular, it can give the actual structure of the staple as it exists in the fleece, and thus assist exact grading.

EFFECT OF SUNLIGHT ON WOOL.

Exposure to sunlight causes wool to become yellow, harsh and brittle. Under the microscope, the scale structure is seen to be damaged. Wool protected by glass plates against weather does not show this destructive effect. Hairs exposed to light lose their doubly refracting property. A N/10 Caustic Soda solution acts differently on exposed and non-exposed fibres. Attempts have been made to distinguish different solubilities in wool which has suffered exposure, e.g., the amount of the fat, etc. Samples of cloth were treated with various reagents—acids, alkalies—wrung out, dried and exposed ; marked light changes were noted. N.B.—It is quite possible that the well-known “ return ”’ or loss of shade of sulphur bleached goods is really an exposure phenomenon. Acid treated materials were strongly affected, alkaline less so or not at all. Light exposed fabrics in many cases dye darker in consequence, but not exclusively ; for example, indigo dyes lighter on such material. * * * * * * * * Some recent papers by Speakman (Jour. Soc. Dyers and Colourists) will probably necessitate a revision of the theoretical structure of the wool fibre given in this chapter.

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CHAPTER XIII.

Textile Cleanliness.

et ee es

Under this title may be conveniently collected many points relating to the lay-out of plant in the scouring and milling shed, the design of machines, and generally all matters bearing on a high standard of technical production. Many such details have been discussed in preceding chapters, e.g., Water Filtration, Alkali Tanks, etc. But there are more general aspects of the subject, such as materials of construction, supply of water, steam, and power, which are best treated collectively.

MATERIALS OF CONSTRUCTION.

The maker of textile machinery is not usually a user of his own plant, and there are therefore a number of details patent to daily observation which do not secure adoption in practice. The scouring and milling of textile fabrics, like the sister art of dyeing, is a branch of applied chemistry. Like all chemical arts, it has to face the problems of corrosion in a more than ordinary degree. Hence the question of materials for the construction of textile plant needs special attention.

IRON.

The non-rusting iron adapted for general practice has yet to be discovered. lIron-rust stains are exceedingly frequent, perhaps the commonest of all, on textile fabrics. All iron- work should, as far as possible, be carried outside the machines. Much framework now done in cast-iron could be better done in mild steel sections with advantages in strength and lightness. The use of ball and roller bearings, which may be enclosed and filled with grease, is advisable in certain cases.

COPPER.

This metal, with its near relation Brass (70% copper, 30% zinc), is a favourite alternative with many machinists, but it is practically as objectionable from the staining point of view ;

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fatty acids in oils or soaps form green copper oleates, etc. The copper pipes in scouring machines, the brass flanges of wringers and milling machines, the perforated copper cages in some laundry type washers and in hydro-extractors, not to speak of copper vessels and such appliances in dyehouses, are all liable to cause trouble if neglected or employed under wrong conditions. 7

LEAD. The conditions of the scouring shed usually permit only of the employment of lead as protective covering ; it is mechanic- ally weak. While it withstands sulphuric acid well, it is open to attack by alkalies and by bleaching chemicals. The lead flashing usual as a cover for centrifugal hydro-extractors should be covered by a wooden ring ; lead is soft enough to rub with coarse wools if in direct contact.

ALUMINIUM.

This is a metal of which far too little use has been made in textile plant. It is practically incorrodible, being very little acted upon by dilute solutions of the common acids or alkalies or the fatty acids; even if slightly corroded, its salts are nearly all white. Its specific gravity is 2.6, and parts made of it are usually lighter even when. bulkier than corresponding details in other metals. Its tensile strength is low, 6 tons per sq. in., but it may often be used in greater thickness. It is generally cheaper, part for part, than copper or brass. One of its greatest defects is its softness, rendering it unsuitable for parts involving mechanical wear. A case in the author’s practice of a successful use of aluminium was as a perforated roller on the blowing machines, substituting copper with great advantages in the cleanliness of the wrappers and of the pieces, and also in replacements. An interesting example of the properties of aluminium occurs in its high specific heat 0.2, for its specific gravity 2.6; iron has a specific heat 0.11, and specific gravity 7.7. If ever the price of aluminium became comparable to that of iron, press plates could be made of the former metal to give the same amount of heat for little more than one-third the weight.

WOOD.

Only a few woods—and these mainly of the white and hard wood type, such as birch, beech, poplar and sycamore—are really suitable for parts of machines with which the fabrics come in contact, particularly rollers, edges of tanks, spouts and mouthpieces of milling machines, and the like. Most woods of the pine class, deals, etc., contain resin; and a large number of the non-resinous woods, such as oak, contain tannin.

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Regard must be paid to the special objects for which the appliance is intended, e.g., pitch pine—one of the most resinous of woods—is very suitable for some tanks where alkalies or soaps do not enter into the question. It must be remembered that most woods resist dilute acids exceedingly well, but alkaline solutions extract tannins, resins, etc., from all but a few such as those above. Machine rollers are so important throughout the ane. scouring, and milling departments, that special notes upon the construction and maintenance are desirable. Soft woods are unsuitable, their porous nature with the effect of water and liquors soon destroying their surface. The best are beech and sycamore, naturally seasoned, and free from defects ; knot- holes, bark-scars, etc., sooner or later cause trouble by decay, leading to mysterious stains. Rollers must be maintained during use in an even, level and smooth condition ; this is best maintained by turning up in position by a slide fixed across the machine ; on this a tool-holder, fed by a screw, carries the turning tool, i.e., an extemporised lathe-bed. The end grain of rollers is the most troublesome to protect from decay. Painting with the common lead paints is unsatisfactory, as the alkaline liquors soon strip this covering. Some attempts at creosoting the ends have been made, with but little success. In one experiment, the rollers were set on end and paraffin wax melted into the grain by heated flat-irons, assisted by a plumber’s blowlamp. Flanging with aluminium sheets up to a couple of inches from the circumference would be a good method of protection. Rollers are commonly made longer than necessary; this is a waste of valuable timber, and prevents access between their ends and the sides of the machine for cleaning purposes. They are also usually heavier than is required ; if more attention were paid to the scour, weight might be saved in the rollers, or the pressure obtained in other ways.

EARTHENWARE.

This material, and also stoneware, combines rigidity with resistance to corrosion ; its brittleness is the great drawback leading to difficulty in making pressure- tight joints. These latter have often to be made by cements of various types, e.g., water-glass solutions with asbestos powder, portland cement, ground pumice, lime, fine ashes, sand, etc.; or bituminous compounds, pitch, rubber, gutta-percha, sulphur, vulcanised waxes, and the like; sometimes screw clamps and packing rings are used. Acid- -resisting stoneware is non-porous, even when unglazed. It is made from siliceous clay ground with water and moulded. After maturing the moulds it is then heated for a fortnight in a special furnace, the contraction

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amounting to 10-15%. Moving parts and joints, such as cocks and flanges, must be ground with emery, and washers _of asbestos or rubber or a layer of paraffin wax or rubber solution employed. ‘‘Ceratherm”’ is a promising material for bleaching, etc., vessels.

SPECIAL MATERIALS.

Some of these of a non-metallic character are of utility in particular circumstances. Indiarubber, though perishable in a comparatively short period by the action of light and air, is useful for many chemical reagents, for roller coverings, etc., especially where flexibility is essential. As hard rubber— ebonite or vulcanite—it is very useful at ordinary temperatures, resisting chemical actions of nearly all types. The sprinkler pipes of scouring machines have been made of it with advantage, its greatest defect being its brittleness. Celluloid, of the transparent kind, is resistant to most ordinary reagents, and is a useful substitute for glass, where it is desirable to see the interior of a machine without risk of breakage of a glass window. The process of galvanisation—i.e., coating with zinc—is perhaps the best available at present for water pipes, tanks for alkali, etc., these being only slowly attacked ; but it is far from being everlasting, and corrosion once set up seems to proceed at an accelerated rate in such appliances. Complete series of pipes, unions, sockets, and fittings generally, with valves also, are now obtainable in ebonite, screwed with standard threads. The lay-out of plant in a scouring and milling shed should be carefully considered, the general principle being that machines follow each other in the order in which treatments are given to the fabrics, to avoid retracing the line of working by pieces already operated upon. The floor of the shed should slope slightly—say, 1 inch in 2 feet—so as to be self-draining and automatically self-cleansing. There should be plenty of room at the back of the machines; more is learnt from the rush of the scour at the draft-board and rollers than from the open front. Tanks for alkali and soap, and filters for water, may be placed along the back, and pipe-runs should be shortened to a minimum against future corrosion. The shafts should be at the back and the driving belts come down from the back. Steam and water pipes are usually laid overhead ; it is debatable whether they would not be better carried in a shallow channel at or near ground level. Drains should slope steeply, to free themselves from flock ; the grids of the seak- boxes are best made of perforated aluminium sheet ; this looks clean and shows up dirty accumulations, and zinc is too easily corroded away. The roofs should be of the familiar saw-tooth pattern, one side glass; the scouring shed should be at least

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as well lit by natural lighting as the spinning rooms. The running of a steam pipe close up to the roof to prevent con- densation has proved useful.

A MODEL DESIGN FOR A ROPE-SCOURER.

In the light of the foregoing consideration, let the design of a rope-scouring machine fitted with all detail improvements necessary for clean and high-class working be now considered. The framework is usually of cast-iron; in these days of cheap and rapid welding by acetylene, etc., it is becoming an open question whether a triangulated frame of mild steel of suitable angle and channel sections would not be equally cheap and much stronger. The trough and sides must be of wood, chosen on the lines of p. 488 ; bad knots, etc., must be drilled out and fresh plugs inserted. The rollers, say, of beech, the lower of smaller diameter. The boardwork might be fastened to the frame by aluminium bolts, in place of the usual wooden pins—or worse, iron bolts—as in this machine there must be no corrodible metal in the interior. The shafts of all rollers are sleeved in aluminium, set into the end grain a little, and carried to the outside of the frame; all bearings are external, and arranged to drip clear of the inside wall of the machine. The top of the machine frame is split into halves for easy removal and replacement of rollers. The bottom of the machine is not quite a symmetrical curve ; -the lowest point is nearer the front of the machine, to form a pool, into which the squeezed folds of the fabric drop as soon as possible and saturate again. The sud-box may be of the ordinary design with holes in the base and slide-block opening and covering these. It should, however, be made double-bottomed, and the lower board brought forward say, 6 inches to spill the squeezed-out scour from the rollers on to the falling pieces much sooner than is ordinarily the case. In general practice, it is probable that 50 out of 60 yards of a piece lie for the greater part of a revolution (60 per minute) in the squeezed-out semi-dry state as they have come from the rollers. This is not scouring ; the pieces in the ideal scouring operation are either being squeezed or being soaked through and through, and the sooner the re-wetting follows the roller action and the better. The best position for the sprinkler pipe for supply of hot or cold water for washing-off is a debatable point. English practice favours positions either in front of the sud-box or lying along the front wall of the machine; in Germany, it is usually placed behind the rollers and just above the draftboard. The best place is probably along the front of the machine. A copper pipe is general, but aluminium would be better. The perforations are usually too few and too coarse; two rows—

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half an inch apart—of one-eighth inch holes pitched half an inch, is a very suitable works arrangement. It is to be noted that the washing-off water does not require to be delivered under more than a head of 5 or 6 feet. A soft packing of Ruberoid, treated felt, or similar material, should be placed between the frame and the boards to prevent rust-creeping by capillary attraction. In such a machine, maintained in good order, fabrics of the highest standard of cleanliness may be regularly turned out.

Fic. 140.—THE Roper Scourtnea MACHINE.

The subjects of materials of construction and corrosion are undergoing rapid investigation, and the gain of efficiency in improving textile plant in this direction is so great that it is desirable to add some special notes.

CORROSION,

that is, the wearing or wasting away of materials by chemical action. This may be by regular use in a given process or by external irregular action of which the commonest and most serious is oxidation. The oxygen of the air is the chief of corrosive substances, and the acids—especially in dilute forms—come next, alkalies and salts being less corrosive. As a rule, increase of temperature and the presence of impurities favour corrosion; especially also under conditions which remove the products and expose fresh surfaces. The junctions

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of dissimilar metals often show excessive susceptibility, which gives some ground for an electrical theory of metallic corrosion.

Cast Iron is more resistant than the other forms :—wrought, malleable iron and mild steel; fine-grained, pure and homo- geneous castings are best and should have the skin retained, if possible. Similar remarks apply to mild steel, which should be low in sulphur and phosphorus. In the special steels, nickel and chrome alloys are manufactured for the anti- corrosive properties. The so-called stainless steels contain 12-14% of chromium, but it must be remembered that their special utility is entirely a matter of conditions. The stainless steels are rustless in air, but do not stand even weak mineral acids. Used as tenter pins on sulphur bleached goods, stainless steel became discoloured. The mechanical properties are often inferior, their brittleness sometimes preventing all machining operations. One of the most interesting and promising of these alloy steels is ‘‘Staybrite,’’ which has very definite resistance to alkaline media and also to the organic acids of the fatty series; it has been produced in all the usual mechanical forms of castings, sheet wire, tube, and perforated plate, and seems likely to meet many of the conditions occurring in textile plant. The sensitiveness of certain metals in special cases must always be bornein mind. Copper is very susceptible to ammonia and its salts, while tin is extremely resistant. Zine resists atmospheric effects well, but gives way at once to dilute mimeral acids. In some instances, coatings are formed which oppose further action, as zinc carbonate in the atmos- phere, and aluminium oxide. In alloys, small quantities of impurities seem to improve the resistance rather than otherwise, e.g., Monel metal, which is a nickel-copper alloy containing iron, manganese, carbon, silicon and sulphur in small amounts.

It is plain that every case requiring the use of anti-corrosive material must be considered on its merits. A sulphur-bleaching plant and machinery presents different problems from a carbonising set and a chlorination outfit for unshrinkable goods. At the same time, even ordinary scouring and finishing machinery, as well as textile plant in general, is full of details which are capable of being modified advantageously in these directions. A number of special applications of aluminium, for example, made by the author, have been mentioned in other connections in this book. Many cases occur in which the difficulties must be circumvented by special devices, e.g., linings and protective coatings, or even by alterations of design.

Linings of cisterns, troughs, vessels, machines, etc., fall into one or other of the following classes :—

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1. TILES, BRICKS, Etc.

Acid-resisting kinds are manufactured under various trade names, for which see the advertisements of the chemical press.

a I ee LA UG (fe A pC LE (Ge ly» PSN YY REG

‘ii RR

Fie. 141.—SCROLL OPENER on WASHER.

(W. Brrou, SALFORD.)

2. VULCANITE, ASPHALT, CELLULOID, Etc.

The first of these, vulcanite or ebonite, is now being used as a coating for rollers, scrolls, cages of hydro-extractors, etc., in conditions where actively corrosive liquids are used, and is a

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splendid material for such work. Asphalt forms excellent flooring, apart from its services in jointing work. Its near relative, bitumen, is very useful in chlorine plant.

3. ENAMELS,

which are silicates capable of flowing over metallic surfaces at comparatively moderate melting points. They offer resistance similarly to glass, and are being more extensively employed, e.g., in dyeing plant of the circulating type. The great objection is the liability to chip and the impossibility of repair.

[° eg 4 ps PRESSURE LEVERS FOR MANGLES Fre. 142.

4. PAINTS, VARNISHES, LACQUERS, Etc. As in other instances, no single preparation meets the entire range of conditions. The ordinary oil paint with heavy metallic base, is not completely waterproof. Bitumen varnishes have proved very useful on wet frameworks of scouring and dyehouse plant; and in wood the asphalt bases are very impervious. In one case, the author melted paraffin wax into the end grain of some machine rollers with a plumber’s blow lamp and ironed it in with a hot flat-iron, scraping away all excess ; this, of course, could not be used in warm liquors.

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THE CUTTING PROCESS.

II

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om

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CHAPTER XIV.

The Cutting Process.

This characteristic dry finishing operation is almost universal on wool cloths. Nearly all fabrics undergo some amount of cutting of their surfaces, varying from the drastic clear cut finish of fine worsteds containing elaborate designs in the weave, to the mere levelling or topping of the long fibres of raised woollens. Comparatively few cloths, e.g., the fleece finished blankets or the frieze finish of hand-woven Harris Tweeds and similar goods, receive no cutting in the finishing routine. It is plain that the Singeing process by which cotton cloths are cleared from loose surface fibre is generally inapplicable to wool fabrics. Apart from the difficulty of removing the products of combustion the handle of the cloth is badly affected. In the burning of wool, different substances of a more or less tarry and combustible nature are formed, rendering it almost impossible to secure complete clearing of the refuse matter. It is instructive to consider the Shearing process from the hostorical standpoint. Before the introduction of the modern perpetual cutting machines, cloths were ‘“‘cropped” by large hand shears, the work being executed length by length of the cloth while laid over a table. It was eminently a skilled art, and in its application to such cloths as the heavy closely-milled raised woollens of the beaver type was a tribute to good crafts- manship and deft manipulation. It could obviously not meet the modern demands for output.

OBJECTS OF CUTTING.

Shearing is one of the few finishing operations which do not involve chemical or physical principles, being a mechanical process solely, and requiring very accurate mechanical adjust- ments in the plant. The improved appearance given to nearly all cloths by the removal of irregular superficial fibre, makes it a normal part of almost all finishing routines. Its

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‘usual place is after tentering, but there may intervene one or more stages of brushing and even a dewing or damping round, the object being to raise all loose fibre and ensure its thorough removal at the cutting blade. As the general aim of cropping is to clear the surface of the cloth and thereby display colour and weave and give sharp definition to fine designs, it is easy to understand when and where cutting is applicable and to what degree it should be carried. On the whole, worsted ‘cloths are well cut ; indeed, one of the characteristic finishing routines on fancy worsteds is intended to produce the Clear ‘Cut Finish. In general, milled and especially raised fabrics receive little cutting. But these broad principles have many modifications. The most drastic cutting is practised on worsted cloth