222 THE JOURNAL OF THE SOCIETY OF DYERS AND COLOURISTS. “oV**18%*

F. E. Craven. E. M. Shaw. R. B. Brown. H. Bindschadler.

Wm.Ackroyd, F.I.C.,F.C.S. John Smith. A. W. Hallitt. W. M. Gardner, F.C.S.

ADDRESSES WANTED.

Brandwood, J., late of 105, Chatterton Road, Ramsbottom. Schultz, F., late of 11, Hiebigegerst Gosse, Berlin.

F. H. Bowman, D.Sc. W. H. Claus. Chas. Dreyfus, Ph.D. A. G. Green, F.I.C., F.C.S.

NEW MEMBERS.

Briggs, Arthur K., 4, Lower Ash Grove, Bradford. Skridla, F., Brookside Print Works, West Leigh,

Lancashire.

W. H. Hopwood. W. Kerr. A. Tuer.

CHANGES OF ADDRESS.

. Barlow, John O., late of 7, Bank Street, Radcliffe, to 23, Manchester Road, Castleton, Manchester.

Brooke, Joseph, late of 5, Park Terrace, Lightcliffe, to Hunsworth House, Cleckheaton.

Brown, Reginald B., late of 18, Warwick Place, Leeds, to 3, Alexandra Terrace, Headingley, Leeds.

Dewhurst, W., late of 8, Nursery Terrace, Pendleton, to 44, Bolton Road, Peudleton.

Vila, H. S., late of 25, South Second Street, Philadelphia, Pa., to 49, South Second Street, Philadelphia, Pa., U.S.A.

SPECIAL NoTIcE.-The Council would be glad to receive copiesofthe Society’s Jonrnal for the.fcllozuing m o n t h s :-

Februarv . . . . . . 1885. May . . . . . . . . . 1885. February . . . . . . 1887. January . . . . . . 1888. March . . . . . . . . . 1888. April . . . . . . . . . 1889. July . . . . . . 1892. August” . . . . . . 1895. February . . . . . . 1896. January . . . . . . 1897. February . . . . . . 1897. April . . . . . . . . . 1897.

If in good condition, one shilling per copy w i l l be for- warded for any of the above numbers sent to the Hon. Secretary, Mr. C. Rawson.

The Journal i s posted free to all Members and Assoeiatos. Non-Nembers can obtain copies on application to the Hon. Sec., Mr. CHRISl‘R. IZAIVSON, 2, Melbourne Place, Bradford. All Orders to be acconipanied by remittance.

Members residing abroad are particularly requested to advise the Hon. Treasurer, Mr. THORP W H I T A U E R , 35, Pemberton. Drive, Bradford, when sending their Subscriptions per Money Orders.

All Communications concerning the West Riding Section should be addressed to the Hon. Secretary MY. G . W. SLATTER, 12, Bronzley Road, Shipley, Ybrks.

All Communications concerning the Manchester Section should be addressed to the Hon. Secretary, Dr. E. KNECHT, Station Road, Crumpsall, Manchester.

Members arereminded that according to Bye-laws 3 and 5 the Journal i s not forwarded to those who have not paid their Subscriptton before the 31st March.

Firms desirous of bringing New Colouring Matters before the Society should send samples, atterns, and par- ticulars to Mr. CHRIST!!. R A WifON, 2, Melbourne Place, Bradford.

All Orders for Advertisements should be addressed to J. ROBINSON, 5, Bond Place, Leeds, to whom all remittances f o r same must be made payable.

DREYFUS SCHOLARSHIP. The Council is now willing to consider applica-

tions for the “ Dreyfus Scholarship,” of the annual value of rE25, for an advanced student, tenable in the Dyeing and Chemistry Department of the Bradford Technical College for one year. Appli- :ations should be made to the Hon. Secretary, Mr. Christopher Rawson, 2, Melbourne Place, Bradford.

RIPLEY PRIZES. The decision of the Judges will be reported to

the Council at its November meeting, and will be communicated immediately afterwards to the competitors.

WEST RIDING SEUTION.

Several Papers are promised to be read before this Section, during the Session, and dates have already been fixed for the following :-

“ Water Purification ” . . . . . . Mr. A. J. CLARK. “The Dyeingof Straw and Allied

Substances ” . . . . . . . . . “ The Microscopic Detection of

Adulteration of Sumach” ... Mr. M. C. LAMB. ‘‘ Indigo” . . . . . . . . . . . . Mr. A. SCHMIDT.

-

Mr. REGINALD BROWN.

MEETING held October 13th, 1898.

Mr. J. B. WILKINSON in the Chair.

THE JANUS COLOURS AND THEIR APPLICATION TO ANIMAL AND VEGETABLE FIBRES.

By M. LIEBEBT, Ph.D.

Even at this advanced stage of chemical research there is yet very little known about the real cause of the dyeing properties of different matters. W e know that certain chemical individuals or complex matters possess dyeing properties to a greater or lesser degree, but we are entirely at a loss to answer the question : Why is that so ?

We have learned to consider as real dyestuffs such bodies, which are not only coloured them- selves, but also possess the pro erty of colouring

animal fibres. You all know that it was an Englishman, W. H.

Perlrin, who invented the Mauveine (1856), that Brat artificial product which found its way into practice. The following years were rich in new discoveries, and English, French, and German chemists all joined in a kind of scientific race, in order to make good use of the acquired chemi-

other bodies, most especially t K e vegetable and

NOV.,~W.I THE JOURNAL OF THE SOCIETY OF DYE& AND COLOURISTS. 223

cal knowledge. The manufacture of colouring matters was soon installed as a new and ever- growing industry.

I n 1869 Graebe and Liebermann discovered a synthetical method of producing the dyeing sub- stance of the Madder plant. It is not necessary for me to dwell on the importance of this dis- covery; you know what it has brought forth; the manufacture of the Alizarines has been of unprecedented value for certain industries, especi- ally in this country, where fast dyeing has always been considered so essential a require- ment. Another new departure in the manufacture of artificial dyestuffs was inaugurated by Bcettiger (in 1884), who discovered the first direct-dyeing cotton colour, the celebrated Congo-red. Since then, the number of direct dyeing products has been increased to legion. Constant study and research have overcome the defects which char- acterised the first members of this group, and the present splendid and beautiful products differ most favourably from these early-discovered sub- stantive colours.

It was found that some of these direct dyeing cotton colours had also so great an a5nity to the animal fibre, that the long-wished-for problem, “ t o dye cotton and wool simultaneously in one bath,” seemed to be solved. Indeed, the effects so produced are in many instances most beautiful. Only one drawback made itself disagreeably felt ; wool, dyed in a neutral or alkaline bath, is always to a greater or lesser degree impaired, and therefore some of its very valuable properties, i.e., strength, lustre, elasticity, handle, &c., more or less lost. This drawback led chemists in all the great colour factories to search for colouring matters which produced uniform effects on both the animal and vegetable fibres, without injuring the nature of either.

The Farbwerke Hoechst claim the merit of having discovered such dyestuffs, and they have given them, according to their double nature, the name of “Janus Colours.” Janus was an old Roman god, who was thought to have had two faces, and the oldest images of this god on Roman coins show him with a double face, the one look- ing forward, the other backward.

It is m y task to-night to speak about these Janus Colours, and I will first give a short review of their properties and qualities in general, and then tell you about the different experiences gained in applying these colours to certain branches of the dyeing industry.

As to the chemical nature of these dye-stuffs, they belong to the great class of azo-colours, and, according to their basic nature, they are chemically styled basic azo-colours. They possess great dyeing power, but are somewhat insoluble. I n order to dissolve them properly and smoothly it is necessary to mix the colours, in a wooden bucket, into a paste with some acetic acid, and then pour boiling water over this paste. I will here mention a strange occurrence which I had an opportunity of observing when making experiments in a large dye-house in Porkshire. The pieces came up rather too reddish in shade, and I told the dyer, or his apprentice, to dissolve

a few ounces of Janus Green B, and add this solution to the bath. I was called away for fifteen minutes, and on my return I was shown that the addition of the Janus Green, far from toning down the red, had proved to have made the pieces redder still. This seemed at first sight strangely puzzling, and I inquired whether there had not been a mistake made in using a wrong tin, but the man who had dissolved and added the colour declared that he had used Janus Green, and nothing else. I n closely examining the matter, I was, however, able to solve this puzzle ; the young d.yer had indeed used Janus Green B, but instead of using a wooden bucket he had boiled the colour with acetic acid in a tin pail. The consequence was, that the acetic acid had acted on the tin and hydrogen gas was generated. You all know that hydrogen gas is a very strong reducing agent, and so it had happened that it had reduced the colour and split it into its components. The damage done was fortunately very trifling, because we could correct the shade by adding some more green, which y e took great care to dissolve properly this time. So much for the dissolving of Janus Colours. I may here add that Janus Red and Yellow are liable to become gelatinous in strong solutions, or when getting cold, but they will easily dissolve again by boiling up.

The Janus Colours dye wool and cotton in an acid bath ; their fastness to light is fairly good, and especially the Janus Yellows are distinguished in this respect. The fastness to washing is satis- factory, and the fastness to water very good. This is especially worthy of note, as it makes the colours suitable for such goods as are waterproofed after dyeing. I n fact, the colours do not bleed when put in water for any length of time. As the colours are dyed in an acid bath, they are not changed in shade by the action of dilute mineral or strong organic acids, and consequently they withstand the action of perspiration extremely well.

As regards rubbing, the colours give very satis- factory results when properly applied. Of course, the most essential thing, in order to get clean colours, is the preparation of the goods before dyeing. It is only natural that wool, which has not been thoroughly cleansed and freed from fatty matters and grease, will dye dirtier than material which has been prepared with all possible care. This applies to all the acid colours, even to those which are known not to rub a t all.

Another point which ought to be carefully observed is, that the water is corrected before dyeing. It stands to reason that water of a very hard nature will give different results from water which is soft. Hard water can be corrected with different acids ; acetic, oxalic, and sulphuric acid are used for this purpose. The acid keeps car- bonates of lime and magnesia well dissolved, and prevents the precipitation of insoluble bases.

I will now describe the application of the Janus Colours to different materials and trades. All classes of union dress-goods, and light material, containing cotton and wool are dyed in a boiling acid bath, with 2 - 4 per cent. sulphuric acid. For reasons which I have just stated, the acid must be

224 THE JOURNAL OF THE 'SOCIETY O F DYERS AND COLOURISTS. LNov., 1898.

added first to the dye-bath, before adding th colour solution. The goods are entered at abou 140-160°F. and then the temperature is slowk raised to the boil, and boiling continued fo an hour. Here again I must mention that th bath is, under all circumstances, to remain acia If, by boiling the goods for a considerable time the wool should absorb the acid, and thus the bat1 become neutral, fresh acid must be added, a otherwise some bases may partially be precipitate( upon the cloth, and produce colour-stains, tha abomination of our trade, which every one of yo1 will have experienced. The more acid thl bath contains, the slower but more evenly thl goods are dyed, which is of great importance fo goods with a smooth wool surface. Although thc addition of more acid revents the thorougl exhausting of the dye-stu H s, it tends at the samc time to increase the levelling, which is, after all the most important point.

Some of the Janus Colours have a greate affinity to wool than to cotton, and others dyc cotton more readily than wool. This is a ver? desirable quality, because it happens only too oftei in our trade, that we have to cover the cotton warp rather more strongly than the wool, in orde to hide defects in the weaving. For this purposi Janus Grey and Brown B are exceptionally suit able, both colours having a greater affinity to thc cotton. On the other hand, Janus Blue R dye wool more readily, while the other J a m s Colour, dye both fibres equally well. Therefore, by usiq a little discretion in dyeing with these colours, a1 the requirements of the trade will be met in ever? way, and with a little practice, all seeming diffi culties will be easily overcome.

Some of the colours, for instance, J a m s Blue R Grey, Red, and Claret, impart in dark shades 2 bronze gloss to the cotton fibre, which is verj undesirable for certain goods, such as union lin ings. Tannic acid, however, will remove thir bronzy appearance, and as the colours, according to their basic nature, easily form tannin-antimonj compounds upon the cotton fibre, such treatmeni will have the effect of increasing the fastness oj the colours generally. The Farbwerke have found a very profitable and efficient method of working 9 cold bath is prepared with 3-4 per cent. tannic acid, 2 per cent. oxalic or sulphuric acid, and 19-2 per cent. tartar emetic ; the goods are passed through this bath, and the bronze gloss will then entirely disappear.

Although this after-treatment with tannin iE easily and quickly applicable, it requires, to all intents and purposes, a second bath, which is not generally liked in this trade (where the profits are not over large). W e therefore have tried to find a still more expedient way of working, without the use of a second bath. An addition of certain chrome salts to the dye-bath will produce the desired effect. But all the different chrome com- pounds do not give the same results ; bi-chrome, i.e., potassium, or sodium bi-chromate, cannot be used for this purpose.

The best results for light shades are produced with chromium fluoride, and for dark shades, chrome-alum is very effective.

The action of the chrome is, up to the present not quite explained, and we are still engaged in investigating this reaction thoroughly. As a matter of fact, the desired effect is gained by adding the chrome fluoride and chrome-alum, together with the acid, to the dye-bath. By usiug 2 per cent. fluoride of chrome, and 2 per cent. acid, or 23-3 per cent. chrome alum, and 1 per cent. acid, the best results are obtained. This addition of chrome-salts to the dye bath has proved especially advantageous to union Italian cloth. The goods can be dyed to pattern in about one hour end a-half, and as they require no second dyeing-process, such as is used in the ordinary course when using sumach, &c., they are distinguished after pressing by a most beautiful lustre and handle, which is no doubt due to the dyeing in an acid bath throughout. I have brought with me a few lengths of union linings dyed in the manner just described with the addition of chrome fluoride and will put them before you for inspection.

But the Janus Colours are not only applicable to light material; they are also of great importance to the heavy woollen district and can be used for serges, presidents, sedan cloths, beavers, &c. Light shades especially come up beautifully level, when dyed with Janus COlOUrs at the boii, and both cotton and wool dye most uniformly and evenly. For medium shades, a combined method of dyeing the wool with acid colours and the cotton with Janus Colours has met with great success. For this purpose, the wool is dyed in the ordinary way, with acid colours, the pieces are then well washed and finally the cotton which is contained in the pieces, either as warp, or scribbled, or spun in amongst the wool, is dyed cold with Janus Colours in the washing-machine or jigger. As the Janus 9010Ur8 have more affinity to cotton than to wool at a low temperature, and especially if the liquid contains acetic acid, the previously dyed wool takes up comparatively little of the dye-stuff and therefore changes little in shade, while the cotton absorbs this dye-stuff rapidly. It is consequently a very easy matter to dye the cotton to the same shade as the wool, and the so produced effects excel as regards uniformity all other methods of dyeing. The patterns which I have brought here have all been wool-dyed first and then the cotton was covered afterwards. In order to shorn the amount of cotton contained in the goods I have divided the patterns. One half illustrates the effect after wool-dyeing, the other half represents the finished goods.

An almost identical process can be applied to 3hoddy goods; of course these have to be stripped Erst, either with vitriol alone, or vitriol and bichrome. For drab and fawn shades the stripped goods are then simply cotton-dyed cold ; for royal blue, green, and brown shades, however, the wool ~s dyed with acid colours, in exactly the same way 5s white goods, before the warps are covered cold n the washing-machine. Acetic acid is found to 3e very useful for this cold dyeing process, inas- much as it helps to keep the wool-face clear, and maltered in shade. But of course sulphuric acid

Novv1W.l THE JOURNAL OF THE SOCIETY OF DYERS AND COLOURISTS. 225

will also answer in most cases. The pattern which I have brought to illustrate the process 01 shoddy goods have been cut off pieces which wen dyed in this neighbourhood. The pieces had i

nasty, dark appearance in the grey and had tc be stripped with about 10 per cent. D.O.V.

I will now pass on to a very remarkable reaction which I observed when first I began to work wit1 these colours. Since the Janus Colours dye in a1 acid bath, I thought it a very natural and self understood fact that they could be toned anc shaded off with the other acid colours. However as it sometimes happens in life the unexpectec takes place, so in this case, instead of brightening the wool, the addition of an ordinary acid coloui produced a thick precipitate and spoiled the experiment altogether. This was strange, and induced us to investigate the matter. W e found that this precipitate did not fall, or if it did dissolved easily again in reheating the liquid wit1 an organic acid, such as oxalic, acetic, lactic, 01 tartaric acid. Making use of this fact, we mixed acetic acid solutions of Janus Red and Patent Blue and boiled two hanks, one of wool and one of cotton in this mixture for 20-30 minutes. The resull was highly interesting ; the cotton hank was dyed red, while the wool hank came up an almost pure shade of patent blue. W e repeated the same experiment with cloth containing a woollen weft and a cotton warp, with' the same result, thus producing a very effective shot effect. In examining the other J a m s Colours, we found that almost all of them produced these shot effects and scarcely changed, or nt least influenced the shade of the wool comparatively little. I have also brought two patterns which were wool dyed first and then covered cold in a second bath with Janus Colours. (I hope that in avery short time, a pattern-card will be put before you, illustrating this process, in its manifold varieties.)

I mentioned before, that an organic acid is to be recommended for this process, and that acetic acid is mostlv used. The pame acid is used when dyeing half-silk goods with J a m s Colours. Such goods are dyed a t . a low temperature, not exceeding 105OF. The bath is charged with 10 per cent. acetic acid, and the dyestuff solution. The wet goods are entered cold, and the cotton dyed to shade first ; then the tempera- ture is raised to about 95OF., and the goods worked, until the silk has acquired the desired shade. The whole process must be chiefly regulated by temperature ; a t a high temperature, silk is dyed darker than cotton, and if the temperature is kept too low, the cotton will appear darker than the silk. I have brought two patterns which will illustrate this effect.

Some of the patterns showing the shot effects have been dyed as just described, viz., in one bath a t the boil, others have been wool dyed first in the acid colour. After working for about one hour, the Janus-colour solution was added (to the same bath), the steam turned off, and the goods allowed to run for about thirty minutes.

Another veryextensive a plication of these Janus

piece goods. Being basic dyestuffs, the Jams Colours will be found in x yeing cotton yarn and

Colours can be fixed in the manner usually applied to tannin colours. They may also be dyed without a mordant, as they possess great affinity to the cotton fibre, but naturally, the so produced effects do not stand very severe treatment, such as hot soaping and washing, well. Another method, however, has proved to be very successful ; if the colours are dyed direct, without previously mordanting the material, they can be fixed upon the fibre, in a second bath, containing tannin, tartar emetic, and sulphuric or oxalic acid. In this fixing bath, the colours are quantitatively converted into their tannin anti- mony compounds, which are so exceedingly fast. Matching requires but little practice, as the shade is changed very little in the fixing bath. I will just give the outlines for dyeing cotton piece- goods and yarns with Janus Colours. I have received these from friends, and they have proved a great success. For yarns, the bath is pre ared with the requisite amount of water, whic \ , of course, must be corrected first with acetic acid. It is heated to about 140°F., 3-5 per cent. sulphate of zinc added, and then the yarn worked in this bath for fifteen minutes. The colour solution is then added, and the yarn worked for another quarter-hour at the same temperature. Then 25 per cent. common salt is added to the bath, and the latter gradually heated to the boil, and the yarn worked for another half-hour.

The second, or fixing-bath, is cold, and contains about two and a half times as much tannin as the amount of the dyestuff used in the first bath. The yarn is worked in this liquid for fifteen minutes, and the solution of tartar emetic (about half of the amount of tannin used) and half a pint of vitriol per every 100 gallons of water are then added. After working the yarn for fifteen minutes cold, the temperature is gradually raised to the boil, and boiling continued for another iuarter of an hour. The yarn is then rinsed, hydro-extracted, and dried.

For light shades, which require 1 per cent., or ess, dye-stuff, an addition of 2-3 per cent. :hromium fluoride to the dye-bath is very useful, t i the colours equalise and exhaust better. For lark shades, however, sulphate of zinc produces the best results. For dyeingyarns, the 15-20- Fold amount of water is required, p+s are dyed n a far more concentrated bath, in the jigger, tnd the 5-6-fold amount of water will be quite iufficient for this purpose. The method of working remains the same. Several ends are Tiven in the sulphate of zinc, the colour is then ~adual ly added, and some more ends given ; then ;he salt solution is added, the temperature raised )o the boil, and several more ends given a t the )oil. Finally, the steam is turned off, and after etting the pieces run for a few more times in the :ooljng bath, they are rinsed and hydro-extracted.

Even for dark shades 3 per cent. sulphate of :inc and 15 per cent. salt will be quite sufficient, 1s the baths contain comparatively little liquid. Phis applies also to fluoride of chrome ; instead of 1-3 per cent., which is required for yarns ; 1 5 2 )er cent. will suffice for piece goods. The second, mfixing bath, is made up exactly as stated for

226 THE JOtJkNAL OB TBE SOCIETY OF DYERS AND COLOURISTS. C N o V v ~ .

yarns ; several ends are given in tannin cold, and then sulphuric acid and tartar emetic added, and a few more ends given ; then the bath is heated t c the boil, some ends given a t the boil, and then the goods rinsed and dried.

I cannot fully describe all the different applica. tions of the Janus Colours to all branches of OUI industry, as I feel that I have fully exhaustedyour patience. I n conclusion I will mention that the Janus Colours have proved to be of great impor- tance to the jute trade ; the jute fibre containe such an amount of tannin that this acts as a very effective natural mordant, and consequently very full shades are produced with comparatively little dye-stuff ; for instance, 2 per cent. Janus Black No. 2 suffices to produce a deep black on jute.

DISCUSSION. The CHAIRMAN said he had no doubt they had

all listened to the lecture with a considerable degree of pleasure. It had given them a very fair idea of what the Janus&olours were, and what might be expected from them. What had struck his mind during the lecture was the absolute necessity of the dyer knowing something about chemistry. The little incident of the colour being mixed in a tin pail, a mistake which might have gone on for any length of time, in the absence of a chemist, strongly illustrated this point. The point also, about the necessity of neutralising hard water impressed upon them the necessity of the dyer having some knowledge of chemistry. A few months ago he happened to overhear a conversation, whilst travelling, between a manufacturer and another gentleman, in some way connected with business. One of these gentlemen said that dyeing, now-a-days, was as easy as tumbling off a chair if the dyer had any sense about him at all, and he suggested that he should have no fear at all in going into a dyehouse and setting to work. It occurred to him (Mr. Wilkinson) that the more they got to know about dyeing, and the simpler the lecturers appeared to make it, the more intricate the whole subject became. They realised this when they observed that with the bringing out of a new series of colours there were so many minute things that had to be attended to, or otherwise the result would be failure. It became all the more necessary for them to know the minuter details of the processes which were involved. It appeared to him that this group of colouring matters was destined, ere long, to make a good deal more impression than had hitherto been the case.

Mr. W. LEACH said he wished to know whether the Janus Colours had been applied to yarns made of mixtures of cotton and wool. As they would be aware, a good deal of business was being done at present in imitating the better classes of woollen goods with mixtures of wool and cotton in order to cheapen them, and there was a large trade being done with mixtures of about 40 per cent. cotton and 60 per cent. wool, which had a very soft handle, and were used for the better classes of ladies’ blouses, tennis flannels, and so on,

When these yarns were dyed with Janus Colours did the uneven appearance as between the cotton and the wool show in anything like the same manner as it did with the union cloths or cotton warp Italians with a woollen weft ?

The LECTURER said that as far as he was able to answer the question the difficulty had been overcome. Some of his colleagues had dyed some yarn containing wool and cotton in varying pro- portions of each, and had issued a pattern card. But up to the present he, however, had not had any practical experience himself, so he could only refer to the pattern card, and whether that showed the difference or not, they would see.

Mr. BINDSCHADLER said he noticed that some of these patterns had rubbed off slightly, and he wished to know whether the lecturer could suggest any remedy for that.

The b w r u a m said that, with the exception of the two large patterns which he had mentioned, the others had been dyed in the laboratory on a small scale, which might account for the rubbing, but he had had no complaints in this respect when dyeing pieces in the dyehouses.

Mr. HALLITT said that he wished to ask whether Dr. Liebert could suggest any special use for these colours in the dyeing of woollen yarns only.

The LECTURER: I n wool dyeing everything depends upon the price on the one hand, and on the fastness of the coiours on the other. I must say that for wool only we have faster dye- stuffs than the Janus Colours.

Mr. HALLITT: Faster to washing? Dr. LIEBERT : Faster to washing, light, milling,

&c. ; consequently one would scarcely replace better products.

Mr. HALLITT: There is no purpose for which you would specially recommend them for wool only?

No, not to my knowledge. Dr. LIEBERT : Mr. HALLITT said another oint which had

the great necessity of keeping up the acidity of the bath. H e had said it would range from 2 to 4 per cent. of acid in dyeing wool and cotton, and spoke of the danger of the wool absorbing the acid from the bath, and the bath in that way becoming insufficiently acid to keep the colours in solution. Was i t within Dr. Liebert’s experience that the wool would absorb so much as 2 to 4 per cent. of acid, and the bath would be neutral.

The LECTURER said he had had experience in dyeing a piece of Italian cloth which contained about 50 per cent. of wool. H e found that after boiling this piece in the bath for an hour the water was neutral. If he remembered rightly he added about 2 per cent. of acid at first, and where he had to add some more colour after- wards he was obliged to add some more acid also. Of course the water had first been corrected.

Mr. HALL~TT : And 2 per cent. over that. THE LECTURER: Yes, about 2 per cent. over

Mr. GARDNER: Probably some alkali from

Mr. HALLITT : It is rather surprising to me that

struck him was the lecturer’s o fl servations as to

that.

the scouring was in the wool.