DYEING OF DEAMINATED WOOL BY W. W. PADDON
The experiments of Richards,l followed by those of Richardson, Dreaper, and Watson Smith, have shown that amino groups are a part of the chemical constitution of wool. It has been believed that the presence of this amino nitrogen in wool might explain the ease with which that fibre is dyed, insofar as the acid dyes are concerned, the free dye acid being attached to the wool through chemical union with these amino groups. On the contrary Bentz and Farrel12 found that wool which had been deaminated by treatment with nitrous acid followed by washing and boiling with either alcohol or water or acidified cuprous chloride solution, “dyes with acidic coloring matters apparently as well as wool in the ordinary state. The dye baths are exhausted in both cases to the same extent and so far as our experiments range are as fast to soaping and light.” The experiments described below verify this work of Bentz and Farrell by obtaining quantitative data regarding the dyeing of deaminated and ordinary wool by typical acid dyes. Pure white sweater yarn was used in the experiments being first washed in dilute soap solution and then rinsed repeatedly in hot distilled water. It was then dried in air and kept in a constant humidity atmosphere. About forty grams of this wool were deaminated by being immersed in 1200 cc of a solution containing 10% by volume of conc. HC1 and 20 grams of sodium nitrite at a temperature of 4 ” C. The temperature of the bath rose from 4 ” C to 10” C and brown fumes were evolved. The wool was kept in this bath with frequent stirring and addition of sodium nitrite for 16 hours. The wool, now yellow in color, was removed and ’Richards: Jour. Soc. Chem. Ind., 7, 841 (1888); Richardson: 12, 426 (1893); Dreaper: 13,95 (1894); Watson Smith: 15, 245 (1896). 2 Bentz and Farrell: Jour. SOC. Chem. Ind., 16, 405 (1897).
Dyeing of Deaminated Wool
385
washed in lukewarm distilled water until the wash waters gave no test for chlorides of nitrous acid. I t was next placed in boiling distilled water and boiled for five hours, the water being repeatedly replenished. The fibre became changed to a very during this boiling, becoming thicker, and shortdark-brown
RDINARY WOOL DEAM IN A E D 5’
Fig. 1 Dyeing with Orange I1
ening to about two-thirds of its original length. The final wash waters gave no test for either nitrous acid or chlorides. The wool was dried in the open room and placed in a constant humidity atmosphere under the same conditions as the ordinary
w.w.Paddon
386
I
wool used in these experiments. A sample of the wool thus deaminated when treated further with nitrous acid and then immersed in alkaline phenol solution underwent no change in color whatsoever. It was therefore concluded that all the amino nitrogen had been removed. In dyeing, two typical acid dyes were used, Orange I1 (duPont) and Lake Scarlet R (National Aniline and Chemical Co.). The following conditions were constant throughout the experiment. Total volume of bath, 250 cc. Milligrams of dye used, 75 mg. Grams wool used in each bath, 1000 gr. Time of boiling, 45 min. Wool entered and removed at the boil. The amount of dye remaining in the bath was determined by titrating with a standard Tic4 solution according to the method of Knecht.l The pH values were obtained by means of a hydrogen electrode of the Lewis, Brighton, and Sebastian type,2 slightly modified. The data concerning the dyeing of the deaminated wool have been compared with the data for the dyeing of ordinary wool previously obtained in this laboratory in the same way by Mr. A. W. Bull. Dyeing with duPont Orange I1 Dyeing of deaminated wool Cc N/lOHCl
2
Final pH
5.75
0.0 0.5 1.0 2.0
4.60 3.80
3.0 5.0
3.40 3.03
10.0 1
1
5.10
2.57
1
Mf2{:tkftI Mg of dye adsorbed 74.0 69.2 57.0 40.5 25.5 17.3
34.5 49.5 57.7
9.0
66.0
Ber. deutsch. chern. Ges., 36, 1552 (1903); 40,3819 (1907). Jour. Am. Chem. SOC.,39, 2250 (1917).
1.0
5.8 18.0
Dyeing o j Deaminated Wool
387
Dyeing of ordinary wool (33.7 11.3 0.0 4.69 51.2 23.8 0.5 4.10 3.80 38.5 36.5 1.0 25.2 49.2 3.32 2.0 16.9 58.1 3.20 3.0 14.5 3.04 4.0 60.5 2.76 12.0 63.0 6.0 69.7 5.3 2.49 10.0 2.00 68.8 6.2 25.0 Dyeing of deaminated wool; stripping effect of Na2S04
I
1
1
1 ;::;:1
I
1
I
1
4.72 11.3 3.14 32.3 Dyeing of ordinary wool; stripping effect of Na2S04 0.3 4.08 61.5 13.5 3.0 23.5 24*7 3.24 46.2 28.8
O 5.0 e5
I
%:;
I
Dyeing with Lake Scarlet R Dyeing of deaminated wool Cc NjlO HCl
Final pH
0.0
0.5 1.0 2.0 3.0 5.0 10.0
::! 1.0 1.5 2.0 3.0
1 I
5.0
8.0 15.0
1
Mg dye left in bath
66.4 6.02 60.9 5.17 52.3 4.99 33.2 4.04 18.5 3.55 3.08 7.7 2.61 1.8 Dyeing of ordinary wool 74.4 6.43 5.58 64.8 4.90 49.4 4.31 35.1 23.7 3.88 7.0 3.37 1.1 2.85 2.57 0.6 2.13 0.2
Mg dye adsorbed
8.6 14.1 22.7 41.8
56.5 67.3 73.2 0.6 10.2 25.6 39.9 51.3 68.0 73.9 74.4 74.8
W . W . Paddon
388
Dyeing of deaminated wool; stripping effect of Na&04 CcN/10 &SO4
0.5 5.0
I
1
%azAio1 24.75 22.50
1
Final pH
4.99 3.15
1
I
Mg dye left in bath
59.G 33.8
1
1
dye :&orbed
15.4 41.2
Dyeing of ordinary wool; stripping effect of Na2S04 25.0 4.55 GG.4 8.6 0.5 3.0 25.0 3.36 31.0 44.0 25.0 2.88 20.5 54.5 5.0
1
1
I
Fig. 2 Dyeing with Lake Scarlet R
1
Dyeing of Deaminated Wool
389
These data have been placed in the form of curves, Figs. 1-2, by plotting milligrams of dye adsorbed against pH values. The curves for deaminated and ordinary wool for the same dye are of the same shape and lie very close together, any difference being well within the limit of experimental error. This is rather surprising in view of the very marked change in the appearance of the wool. The above quantitative experiments show that the amino groups in wool play no part whatever in the dyeing of that fibre by acid dyes. The work has been carried on under the supervision of Professor Bancroft, and was made possible by a grant from the Chemical Foundation. Cornell University
