BY A . 1%'. DAVISON
This work was undertaken in order to collect data which could be used in devising laboratory and lecture experiments on the theory of dyeing. Though the results are not new in principle. they seem interesting enough to warrant publication. The first experiments were on the behavior of basic and acid dyes in alkaline, neutral and acid solutions. A basic dye is one in which the color is in the basic radical: magenta, safranine, auramine, malachite green, methylene blue. crystal violet, and Bismarck brown, for instance. An acid dye is one in which the color is in the acid radical: crystal ponceau, croceine orange. naphthol yellow, cyanine blue, and acid \-iolet, for instance. X basic dye should be taken up more completely in an alkaline solution than in a neutral solution, and least of all in an acid solution. An acid dye should be taken up more completely in an acid bath than in a neutral one, and least of all in an alkaline solution. Addition of sodium sulphate should cut down the adsorption of acid dyes and increase the adsorption of basic dyes. In each case a small amount of dye was dissolved in 300 cc water, the solutions usually being so dilute as t o be quite transparent. The solutions were then divided into three equal parts. One was called the neutral solution and had nothing added t o it. To the second portion I cc 6 S HC1 was added. this portion being afterwards called the acid solution. The alkaline solution was prepared by adding I cc 6 -1-XaOH t o the third portion. The wool was the best all-wool flannel t h a t could be bought and was cut into strips approximately two inches by six. The cotton was heavy unbleached muslin cut into strips of about the same size. T h e wool and the cotton were bought a t a local dry goods store and were used as bought. The strips were placed in cold solutions which were then heated to boiling for thirty minutes, after which the strips were washed and dried.
The first experiments were made with acid dyes on wool. Fast Green (Elberfeld) dyed wool more deeply in acid solution than in neutral solution; in the alkaline solution practically no dye was taken up by the wool If a large amount of acid ( I O cci be added to roo cc of the dye solution, the wool does not take up as much dye as from the neutral solution. Acid Green B. B. S Y. (Elberfeld) illustrates admirably the effect of acidity and alkalinity. The woolen strip from the acid solution was dark green; the one from the neutral solution was light green, while the one from the alkaline solution was apparently not colored green a t all. IYith &AcidViolet 3R (Elberfeld) the acid and the neutral solutions dyed approximately to the same hue, the strip from the alkaline solution was much lighter Croceine Orange iElberfeld) behaved much the same way, there being very little difference betn-een the strips from the acid and the neutral solutions, while the one from the alkaline solution is much less colored Alizarine Yellow [ Elberfeld) gave no satisfactory results, the wool being colored about the same dirty yellow in all three solutions. Chromium is usually used as a mordant n-ith this dye when dyeing wool, so perhaps this was not a fair case Fast Blue 0 (Meister, Lucius and Bruningi was tested in fairly concentrated solutions The strip dyed in acid solution was colored deep blue, the one in the neutral solution was somewhat less blue and the color tended to a drab; in the alkaline solution the color was a bluish drab There is the normal change in depth of color, but there is also an abnormal change of color. The dye is given in the books as a mixture of the sodium salts of triphenyl-p-rosaniline-monosulphonic acid and of triphenylrosaniline-monosulphonicacid The dye apparently gives quite different shades with varying concentrations. The tendency to dye greenish drab increases in neutral solution with increasing dilution E\-idently the most concentrated neutral solution was not concentrated enough to give the same color as the acid solution. Addition of S a O H changes the color of the solution to a reddish brown.
A series of runs were now made with basic dyes on wool. Emerald Green \ Elberfeld) was tried in concentrated solutions and in dilute solutions. The gradations are excellent, the color being deepest in the alkaline solution and lightest in the acid solution Addition of too much S a O H decolorizes the solution, a pale green precipitate being formed. X large amount of HC1 causes the solution to turn reddish yellow. Seither of these difficulties occurs with the solutions actually used. Care must also be exercised with Victoria Blue B (Elberfeld) Boiling a solution of this dye causes turbidity, owing to the separation of the free base The addition of concentrated hydrochloric acid causes the separation of a blue precipitate which changes to green and then to a dark reddish brown. Three sets of experiments were made with this dye. U-ith a concentrated solution the acid bath dyed the wool a beautiful blue. the neutral one dyed a deep purple and the alkaline bath a dark blue with a suggestion of purple. TTith a dilute solution, the deepest color was obtained in the alkaline solution n-hich is as it should b e , but the acid bath gave a deeper color than the neutral one, the color in this last bath tending to a drab JTith a solution of medium concentration the neutral bath $1-es a deeper shade than the acid bath ; but the alkaline bath did not seem to dye the wool more than superficially and the tint was distinctly off-color. n'hen dJ-eing wool or silk, Victoria Blue is usually used in an acetic acid solution; for cotton, tannin and tartar emetic are used as a mordant Thioflavine T ( Matheson) gives very satisfactory results in neutral and acid solutions, the color being lighter in the acid bath Addition of alkali causes a greenish precipitate to form, which. of course, makes this part of the experiment worthless. Chrysoidine AG (Matheson) gives a deeper color in alkaline solutions, but there is T'ery little difference between the neutral and the acid baths. Safranine 0 Meister, Lucjus and Bruning) gives admirable gradations especially when rather dilute solutions are used. As illustrating the general theory, Acid Green B. B. S .Y .
(Mberfeld) is perhaps the best of the acid dyes tested, while Emerald Green (Mberfeld) and Safranine 0 (Meister, Lucius and Bruning) are t o be recommended among the basic dyes. A few experiments were also made with cotton. I n general the effect of acidity and alkalinity is not so striking with cotton as with wool; but the same relations hold. A more concentrated XaOH solution was used than in the experiments on wool. With a more dilute solution there would have been less trouble from precipitation. JVith the acid dye, Fast Green, an excellent gradation was obtained. the cotton strip dyeing a light green in the acid bath, scarcely in the neutral bath, and not a t all in the alkaline bath. Acid Violet and Croceine Orange also work well, a good color being obtained in the acid solution and practically no color in the alkaline bath. Fast Blue dyed cotton a light blue in the acid bath ; b u t the neutral and alkaline solutions had practically no dyeing power a t all. With Alizarine Yellow the shade was the same from the neutral and the alkaline solutions. Hydrochloric acid precipitated the dye and there was consequently no color taken up from this solution. Of the basic dyes Safranine was the one which gave the most satisfactory results with cotton. The color from the acid bath was a pale pink, from the neutral bath a red, and from the alkaline bath a deep red. With Emerald Green a light green was obtained from the acid bath and a beautiful dark green from the neutral bath. Addition of too much alkali causes precipitation of a light green precipitate. It is probable t h a t a more dilute alkali would have given satisfactory results, as was the case with wool; b u t this was not tried. Thioflavine dyed more strongly in the neutral solution than in the acid one; but the alkaline solution did not work well, owing t o precipitation. As was the case with wool, Victoria Blue did not work well in alkaline solution owing t o the change of color. Though the neutral bath dyed more deeply than the acid one, the general effect was not so satisfactory. A few experiments were next made t o determine the effect
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741
of sodium sulphate on neutral baths, care being taken that the only difference should be in the sodium sulphate content. To ensure this a solution of 15 grams Na2S04.10H20in IOO cc water was made up and also 2 0 0 cc of a dilute solution of the dye. The dye solution was divided into two equal parts, 2 0 cc of the sodium sulphate solution being added to the one portion and 2 0 cc water to the other portion. IVith Acid Green, Croceine Orange and Fast Blue, the wool is dyed a deeper shade in the solution containing no sodium sulphate, the sodium sulphate preventing the dye from being taken up by the wool. n'ith Croceine Orange the color is more yellow as well as lighter when the wool is dyed in the solution containing sodium sulphate. Emerald Green, Victoria Blue and Safranine were taken as the basic dyes and, in each case, less color was taken up by the wool from the solution containing no sodium sulphate than from the solution which does. The results with the basic dyes are the exact reverse of those with the acid dyes. This makes rather an effective experiment. Some experiments were next made with varying concentrations of sodium sulphate to see whether the effect due to the salt passed through a maximum or a minimum a t any concentration. Solutions were made up containing constant quantities of the dye and amounts of crystallized sodium sulphate varying from 16 grams per IOO cc (practically saturated) through 8, 4, 2 , I , ?, 1, ' 8, 16, to ' 32 grams per IOO cc in some cases. T o secure uniformity, the solutions were heated to boiling ; the woolen strips were put in and boiled for an hour aster which they were removed, washed by dipping into distilled water, and dried. To determine exhaustion, qualitatively, the solutions were brought again to IOO cc with water and the relative depths of color noted by the eye. There seemed to be nothing to be gained by making quantitative determinations of exhaustion. I n all cases checks were run with dye solutions containing no sodium sulphate. The first runs were made with Brilliant Blue Extra Green Shade (Elberfeld) because outside information had made it
seem probable that this dye would give abnormal result\. The woolen strip in the most concentrated Glauber'i salt solution (practically saturated) took up but little color from the bath As the concentration of the Glauber's ialt decreased to o j gram per IOO cc. there was a continuous increase in the depth of the color of the wool, but beyond this point there was no marked change The bath containing o j gram S a 2 S O iIoHJO per I O O cc seem to dye more evenly than the more dilute solutioni The degree of exhaustion of the baths varied continuously, increasing with decreasing concentration of sodium sulphate II'ith Safranine the gradation ii e\-en better and can be followed through the whole seriei The qtrips dyed in the more concentrated solutions are the darkest and those in the most dilute solution the palest The order is the reverse oi t h a t with Brilliant Blue. just as it should be The degree of exhaustion of the baths also varies continuously, being greatest in the solutions with high concentrations of Glauber's salt and least in the dilute solutioni n'ith Croceine Scarlet the dyeing was more intense and the degree of exhaustion greater as the concentration decreased from 4 grams Glauber's salt pes IOO cc The baths containing 16 grams and 8 grams per IOO cc did not fall in line but there was also a distinct color change in these two cases, so t h a t it is probable that there had been an actual change in the dye. Tl'ith Benzopurpurine and wool there was T ery little difference in shade with T arying concentration of sodium sulphate, though dyeing took place more evenly in the solutions containing little or no sodium sulphate I n spite of this, distinctly abnormal results were obtained as to the degree of exhaustion of the baths. Those containing 16 grams and S grams per I O O cc were almost colorless, with a colored precipitate in the bottom of the flask The apparent degree of exhaustion was next greatest in the bath containing 4 grams S a a S 0 4 . 1 0 H 2 0per IOO cc. This was followed by the bath containing no sodium sulphate The 2-gram bath was more colored and the I-gram bath was the most strongly colored I
of all, A second run with new solutions gave the same result, Since the difficulty was evidently due to the formation of colored precipitates, the woolen strips were omitted and fresh solutions of the dye were boiled in presence of varying amounts of sodium sulphate. I n each case heavy precipitates were formed, the supernatant liquid being only slightly yellowish. This is enough t o account for the abnormal exhaustions. \Then cotton strips were substituted for the usual woolen strips and were boiled in freshly prepared dye baths, very satisfactory results were obtained. The lightest strip was the one from the solution containing no sodium sulphate and there was a gradual increase in the darkening as the concentration of Glauber’s salt increased. The results on exhaustion were more nearly normal than with wool, though there were colored precipitates a t concentrations of Sa2S04.10H20down to 2 grams per 100 cc; but the bath having no sodium sulphate was much more high11 colored than those with increasing concentrations of this salt. Glauber’s salt is frequently employed in the dyeing industry to prevent a streaked appearance in the finished product and to cause the dye to penetrate farther into the fabric. The consequence is that the fabrics are dyed more even1)- both on the surface and on the inside of the goods. T h a t sodium sulphate causes a more even dyeing has been explained on the ground that the salt prevents the fabric from taking up the color so readily as it would otherwise do. Since the bath is not exhausted quickly, the dye has ample opportunity to come into immediate contact with all portions of the fabric before i t is adsorbed; consequently, all parts are colored evenly when adsorption takes place. I n order t o test this hypothesis, two IOO cc solutions were made up of equal concentration as regards the dye; but one contained I gram Na2S0 .IoH?O per 100cc while the other did not. Both were heated to boiling, and sis small woolen strips were placed simultaneously in each. At the end of j , I j , 2 j , 3 j , 45 and j j minutes, respectively, one strip mas removed from each bath, washed, and
allowed to dry. An inspection of the strips gave qualitative information as t o the rate of adsorption in the two baths. With Acid Violet the color of the samples deepened with the time of immersion up t o 45 minutes, after which there was no appreciable change because the baths were nearly exhausted. The exhaustion was greater in the bath containing no sulphate and the samples from this bath were always slightly darker than the corresponding ones from the bath containing sulphate. Though the sulphate cuts down the rate of adsorption, it also cuts down the total amount of dye adsorbed. The same effect was obtained with Acid Green, so that the usual explanation for the action of sulphate is not entirely correct. As a preliminary t o experiments on mordants, some experiments were made with lakes, prepared by precipitating a mordant in presence of the dye and in the absence of the fabrics. Aluminum hydroxide was precipitated from the sulphate solution by means of sodium hydroxide. This, of course, carries down some sodium sulphate. Aluminum hydroxide was precipitated from aluminum acetate, not necessarily in solution, by means of sodium hydroxide. A tannin lake was obtained by the action of tartar emetic on a tannic acid solution in the presence of ammonium chloride. The first lot of alumina lakes were prepared by dissolving 8 grams aluminum sulphate in 50 cc water, adding enough dye to give the solution a faint color, and just precipitating all the alumina with caustic soda. The mixtures were allowed t o stand in cylinders until the precipitate settled so t h a t one could be certain whether the supernatant liquid was colorless or not. Alumina does not decolorize solutions of the following dyes completely : Fast Green ; Acid Green ; Croceine Orange ; Fast Blue ; Emerald Green ; Victoria Blue ; Thioflavine ; Chrysoidine ; Safranine. Alumina takes out nearly all the color from Alkali Blue and decolorizes a dilute solution of Acid Violet. A dilute solution of Alizarine is decolorized completely, a pink lake being formed. IVhen a more concentrated solution is used, the color is not taken out so completely b u t the lake is dark
Experinzents in Dj’eiiig
745
red. Solutions of Alizarine Green, Benzo Orange, Alizarine Orange, and Coeruleine decolorize well. A very dilute solution of Alkali Blue decolorizes completely. With Alizarine Black the supernatant liquid is somewhat yellowish; but otherwise this dye is very satisfactory. Solutions of Alizarine Blue and of Anthracene Chrome Blue are not decolorized satisfactorily by alumina. Chromium hydroxide is intended to be used as a mordant with Anthracene Chrome Blue; but no attempt was made to determine the behavior of the chrome lake. T o a dilute solution of .llizarine Blue 60 cc of a water glass solution were added and the silicic acid then set free by hydrochloric acid. The silicic acid did not carry down the Alizarine Blue. I n cases where alumina causes little or no change in the color of the solution, it is impossible to say, by inspection whether the alumina is colored a t all or whether the color t h a t one apparently sees is due to the colored solution surrounding the precipitate. In cases of this sort the precipitate was filtered and washed. ‘The dyes were added in small amounts t o separate stand-glasses, each containing j o cc water and 8 grams aluminum sulphate. The lakes were precipitated with NaOH as before and were allowed to stand for a week, after which they were filtered and washed with cold water, care being taken to note the appearance and color of the original lake, solution, and residue after filtration; also of the precipitate after washing, and of the wash water. U‘ith Fast Green alumina seemed to carry down no color a t all, the solution being apparently as intensely colored as before the alumina was precipitated. The filtered precipitate was almost white and one washing took out all the color. There is therefore no appreciable adsorption in this case, the slight color of the precipitate being due to mother liquor. Acid Green behaves like fast green. There is no perceptible decolorization of the solution and one washing leaves the alumina colorless. Acid Violet was carried down completely by alumina, as has been previously stated. When the pink lake was washed, the filtrate was colorless, so this lake is “ f a s t ” to cold distilled water. When a very dilute solution of
Alizarine Yellow is taken, the resulting lake does not color the wash water. Alumina is colored but slightly by Croceine Orange and one washing removes all the color. Starting with a more concentrated solution of Fast Blue than usual, a light blue lake separated and the color of the supernatant liquid was less intense than before. n'hen the bluish lake was washed, the color decreased in intensity and the wash water was distinctly blue. This seems t o be a case where there is some adsorption but where the distribution coefficient is such that water takes out the dye gradually, the color not being fast. Emerald Green seerried to be taken up somewhat by alumina b u t the color washes out a t once and the apparent color of the lake is therefore probably due to mother liquor. n'hen alkali is added to Victoria Blue the color changes to a paler brown. X pale reddish brown lake is formed which does not yield any color to the wash water. n'ith Thioflavine the alumina is so obviously colorless that the solution was not even filtered. IYith Chrysoidine the filtered lake appears slightly colored; but the first washing removes the tint. Il'ith Safranine the alumina seemncd slightly colored h u t the first washing removed the color. This case differs from the preceding ones in that the filter paper was colored deeply by the original solution and prolonged washing did not remove all of the color though it did take some of it out. Of course this is not specially surprising hecause Safranine is used as a stain in histological work. It makes a very good experiment however. Bits of clean filter paper were next shaken up with some of the unwashed, slightlj- colored alumina and with pure water in an Erlenmeyer flask. The alumina was decolorized, part of the color going to the filter paper and part to the water. This is what one mould expect because the water would wash the color out of the alumina while the filter paper would take up its proportion from the water. UTth aluminum sulphate we are precipitating alumina from a soluble salt. It seemed worth while to see what would happen if one started with the sparingly soluble aluminum acetate. IYjth this salt it would be possible to add calcium acetate if desired. and the presence
of a calcium salt is considered essential when dyeing with alizarine. A dilute solution of the dye was made and a 30 cc portion was placed in each of two cylinders. To each solution was added 0.5 gram solid aluminum acetate (no analyses made). T o one of the solutions was added as much solid calcium acetate as would go on the tip of a small knife blade. The mouths of the cyiinders were closed with rubber stoppers and the mixtures were shaken thoroughly. Caustic soda solution was added, a little a t a time. until no undecomposed aluminum acetate could be seen after shaking. A n excess of alkali must not be added or the alumina will go into solution. The cylinders were allowed to stand until the lakes had settled. 11-ith Fast Green the lake settled rapidly in the cylinder to which calcium acetate had been added. The alumina was colored a deep green but there was some color in the supernatant liquid. The precipitate settled in the course of a felv hours in the cylinder containing no calcium salt. X good deal of color was carried down by the alumina but not so much as when the calcium salt was added. I t is interesting t o note that alumina prepared from aluminum acetate carries down much more color than alumina prepared from a sulphate solution. 113th Acid Green as dye, the lake settled a t once in the solution containing lime ; but did not take down all of the color. I n the solution containing no calcium salt, the lake settled over night. I t seemed to be more deeplq- colored than the corresponding lake containing lime, thus reversing the phenomena obtained with Fast Green. So far as qualitative tests go Acid Green is adsorbed to a lesser extent than Fast Green. 1Tith Acid Violet 3R both lakes carried down practically all the color. The only apparent difference is that the lake settled almost immediately in the solution containing lime and much more slowly in the other case. U-ith Croceine Orange the settling was more rapid in the solution containing lime and nearly all the color was carried down. The exhaustion of the bath was not nearly so complete in the solution containing no calcium salt. Both the solutions of Alizarine
Yellow changed to red on the addition of caustic soda but returned t o their former color when the base had reacted with the aluminum acetate. I n both cases the lake removed nearly all the color; so t h a t the only noticeable difference was the rapidity of settling when calcium acetate is present. The solutions of Fast Black 0 (Meister, Lucius and Briining) turned pale pink when alkali was added and then did not turn back completely, probably because a slight excess of base was present. The precipitate settled a t once in the solution containing lime and the lake appeared to carry down all the color. The precipitate in the other solution settled over night and carried down most, but not all, of the color. ITith Emerald Green and Chrysoidine, practically no adsorption took place from either solution. The presence of lime caused a more rapid precipitation. The solutions of Victoria Blue turned pink on addition of alkali. The lakes were reddish brown and removed practically all the color. The increased adsorption of the acid dyes, Fast Green, Acid Green, Acid Violet, Croceine Orange, Alizarine Yellow, and Fast Blue when no sulphate is present, is undoubtedly in line with the action of sodium sulphate in preventing these dyes from being taken up by wool. It had been hoped t h a t sodium sulphate would cause the basic dyes, Emerald Green and Chrysoidine, to be taken up more readily by alumina; but this seems not t o be the case. The cases would be more nearly parallel if we had a basic dye which was adsorbed appreciably by alumina. It is conceivable t h a t the sodium sulphate acts as it should but t h a t the difference falls within the limit of experimental error. This is a plausible assumption because it has been found t h a t a saturated solution of sodium sulphate will not strip alumina lakes of Alizarine or Alizarine Black when these are prepared from aluminum sulphate solution. The rapid settling of the lake in presence of calcium salt is in line with the general behavior of colloidal suspensions. It is worth noting t h a t the apparent volume of the precipitate was always greater in the solutions containing calcium salts than in the corresponding solutions containing none.
Ex perinzeTtts ii? Dyeing
749
There are several possible ways of accounting for this. The precipitate might be less dense and therefore more bulky in the one set of cases; the precipitate might actually be heavier, owing to the presence of calcium hydroxide; or the precipitate might actually be heavier owing t o more complete precipitation of the alumina. The third assumption does not seem probable because the supernatant liquid does not seem less clear in one case than in the other. While the second assumption is undoubtedly true, so little calcium acetate was taken t h a t it does not seem probable that the calcium hydroxide could account for the difference. It seems more plausible t h a t the rapidly coagulated gel contains more water than t h a t which has precipitated slowly. As this is really a problem in general colloid chemistry rather than in the special subject of dyeing, no work was done on this point, interesting though i t is. The a i d e use of tannin with potassium antimony tartrate in connection with the mordanting of basic dyes upon cotton suggested the preparation of tannin lakes with basic and acid dyes. Accordingly, cylinders containing about j o cc each of dilute solutions of various dyes were arranged in a row; to each cylinder was added about a heaping tablespoonful of tannin. The cylinders were shaken thoroughly to cause apparent solution of the tannin, and j cc molar ammonium chloride added t o each stand-glass. The lakes were then precipitated by adding sufficient tartar emetic solution, little by little. The precipitates were allowed t o settle for 2 hours though this was longer than was necessary. Experiments were made with the acid dyes, Fast Green, Acid Green, Acid Violet, Croceine Orange, Alizarine Yellow, and Fast Blue; and with basic dyes, Emerald Green, Victoria Blue, Thioflavine, Chrysoidine and Safranine. In every case the precipitate carried down practically all the color regardless whether the dye was a basic or an acid one. These lakes did not bleed when washed with water. Unless ammonium chloride is added no precipitate forms and we are apparently dealing with a colloidal solution of the lake analogous to some of the
writing inks. It makes no difference, however. whether the ammonium chloride be added before or after the tannin and the tartar emetic solutions are mixed. If added after the mixing, the ammonium chloride causes the precipitation of the lake. Experiments were next made on cotton mordanted with tannin, with and without tartar emetic. Cotton strips were boiled for I hour with tannin and water, mere dried, arid then were treated with solutions of basic dyes. Thioflavine dyed the cotton well and Victoria Blue very poorly ; Emerald Green gave a good green; Chrysoidine, a brilliant orange and Safranine a deep red. The strips were boiled with distilled water for an hour t o fade them if possible. The strip dyed with Emerald Green faded a great deal, the cloth becoming a light green and the solution turning p i ~ k . The pink color being unexpected, the solution was decanted and was used to dye wool and cotton. n'ool dyed slightly green, leaving the solution still pink: while the cotton turned greenish with a pink tinge, the solution being then very pale pink in color. T o determine whether the pink color was due to a reaction of the dye with tannin, a solution of the two were boiled without any cotton being present. The color remained green and no change t o pink could be detected. The strip dyed with Thioflavine bleached a great deal, the solution becoming colored slightly yellow, while a flocculent, yellow precipitate formed in the bottom of the beaker. This precipitate is undoubtedly a thioflavine lake. The strip dyed with Chrysoidine faded considerably, the water taking on a deep orange color. The strip dyed with Safranine also faded a great deal, the solution becoming deep red. The strip dyed with VictoriaBlue faded but little and imparted but a slight color to the water ; but this is probably due in part to the fact that the cotton had only taken up a little of the dye originally. To study the mordant action of tannin and tartar emetic combined, cotton strips were soaked in a cold tannin solution, dried, passed through a solution of potassium antimony tartrate, dried, and then dyed in a neutral bath. The strips
were dried, and a small sample cut from each to act as a check, The strips were then boiled with water for 4 hours to make them fade. Izmerald Green and Victoria Blue did not dye smoothly, the cloth being spotted. The spotting with Emerald Green seems t o be due to air bubbles adhering t o the fabric and keeping dj-e solution from wetting it completely. Fast Green and Acid Green dyed well but faded considerably; Acid Violet and Croceine Orange dyed very well but faded out nearly completely. Fast Blue dyed well, but faded almost completely. Alizarine Yellow did not dye a deep shade b u t did not fade much. [ t is worth noting that while Alizarine Yellow is fairly fast when mordanted with tannin and tartar emetic, it does not dye cotton readily. The dye seems to be adsorbed slowly; b u t the mordant holds it well after it has once soaked in. Emerald Green dyed a fairly good color but spotted; i t did not fade. Victoria Blue dyed l-ery poorly but did not fade. Thioflavine. Chrysoidine, and Safranine dyed beautifully and were fast. There is very little fading with the basic dj-es while the acid dyes are not fast with the exception of Alizarine Yellow. Since soap is used t o some extent as a mordant, strips of cotton were boiled for an hour in a concentrated soap solution made from yellow laboratory soap. The strips were allowed to dry and were then dyed in a neutral bath. Checks were run with strips which had ncjt been treated with soap. The dyes used were Emerald Green, Victoria Blue, Thioflavine, Chrysoidine, and Safranine. I n every case the strips which had not receix-ed the soap treatment dyed much deeper than the others. n’hen boiled with water, the color was much faster in the strips which had received the soap treatment. After 16 hours’ boiling with water, the strips were still fading a little and there was very little difference between the two sets. The experiments, like the one with tannin alone, were not quite fair from the dyer’s point of view because soap is not ordinarily used without a fixing agent. Another set of runs was therefore made, in which the cotton strips were boiled
752
A. It'. Dw' Lzson
for I hour in a dilute soap solution and then dried. They were next placed for 30 minutes in a cold solution of soda alum, after which they were allowed t o drain and dry partially for an hour. They were boiled for an hour in a neutral dye bath. As before, checks were run with cotton strips which had not been treated with soap and with alum. The dyes used were the same as before. I n each case the treated strip took up more color than the untreated strip. When boiled with water twice for an hour each time, the mordanted strips, which had been dyed with Emerald Green or Victoria Blue, faded very slightly if a t all, while the untreated strips faded considerably. With Thioflavine and Chrysoidine the untreated strips did not fade so much as did the untreated dyed with Emerald Green or Victoria Blue; b u t they faded much more than the corresponding, mordanted strips. The sodium oleate, which is the important item in the soap, apparently cuts down the amount of dye which the cotton will take up; b u t what dye is taken up becomes practically fast t o boiling water. The general results of this paper are as follows: I . Acid dyes should be taken up more completely in an acid solution than in a neutral one and least of all in an alkaline solution, while the reverse should be true with basic dyes. Good gradations can be obtained on wool with Acid Green and Emerald Green; on cotton with Fast Green and Safranine. 2 . Marked differences between the dyeing in acid and alkaline solutions can be obtained on wool with Fast Green, Fast Blue, Acid Violet, Croceine Orange, Crystal Ponceau, Chrysoidine, Safranine, and Methylene Blue; on cotton with Acid Violet, Croceine Orange and Emerald Green. 3. Addition of sodium sulphate should cut down the adsorption of acid dyes and increase the adsorption of basic dyes. Excellent results are obtained on wool with Acid Green, Fast Blue, Croceine Orange, Victoria Blue, Chrysoidine and Safranine; on cotton with Benzopurpurine. 4. The effect of continuously varying concentrations of sodium sulphate is shown well on wool with Brilliant Blue and Safranine : on cotton with Safranine.
E xperivzeTzts i71 D y e i n g
753
5. Alumina, precipitated from an aluminum sulphate solution. carries down practically no Fast Green, Acid Green, Croceine Orange, Emerald Green, Thioflavine, Chrysoidine, or Safranine. There is a slight adsorption of Fast Blue and Victoria Blue, but not enough t o decolorize even a fairly dilute solution. 6. Alumina, precipitated from an aluminum acetate solution adsorbs Fast Green, Acid Green and Croceine Orange considerably but not Emerald Green or Chrysoidine. Presence of sulphate decreases the adsorption of the acid dyes by alumina as well as by wool. 7. m'hen calcium acetate is added t o the aluminum acetate solution, the alumina carries down more Fast Green and Croceine Orange but less Acid Green. I n all cases the lake settles faster in the solution containing lime. 8. Alumina, precipitated from an aluminum sulphate solution, decolorizes dilute solutions of Alizarine, Alizarine Green, Benzo Orange Coerulein and Acid Violet practically completely. Alumina, precipitated from a n aluminum acetate solution, decolorizes inore concentrated solutions. 9. Tannin, tartar emetic and ammonium chloride carry down Fast Green, Acid Green, Acid Violet, Croceine Orange, Alizarine Yellow, Fast Blue, Emerald Green. Victoria Blue, Thioflavine, Chrysoidine, and Safranine practically completely. The presence of ammonium chloride is essential t o precipitate the hydrosol. These lakes do not bleed when washed with water. I O . When cotton is mordanted with tannin and tartar emetic, it dyes well with Thioflavine, Chrysoidine, Safranine and Alizarine Yellow; the colors stand washing with water. The cotton dyes well with Fast Blue, Fast Green, Acid Green, Acid Violet, and Croceine Orange but the colors fade when washed with water. I I . When cotton is treated with soap, i t takes up Emerald Green, Victoria Blue, Thioflavine, Chrysoidine and Safranine less completely than the untreated cotton; b u t the color washes out less rapidly,
I 2 . When cotton is treated with soap and alum, it takes up Emerald Green, Victoria Blue, Thioflavine and Chrysoidine less completely than the untreated cotton. n'ith Emerald Green and Victoria Blue, there is only a slight fading on washing with mater; with the Thioflavine and Chrysoidine there is considerable fading b u t not so much as when no alum is used. This investigation was suggested by Professor Bancroft and has been carried on under his supervision.
Cor71ell 1.11i i c r b i t j
