10 



BULLETIN 366, U. S. DEPARTMENT OF AGKICULTUEE. 



BLEACHING OF YARNS. 



The material used in these bleaching tests consisted of yarn made 

 from the following samples of cotton : 1 and la, 2 and 2a. Samples 

 1 and 2 had been fumigated, and samples la and 2a were nonfumi- 

 gated. 



All four samples were treated as follows : Boiled for two hours in 

 10 per cent solution of soda ash at atmospheric pressure, rinsed until 

 free from alkali, then divided into two lots, each lot containing one- 

 half of each of the above four samples. One lot was bleached by 

 method A, the other by method B, as follows: 



Method A. Treated cold for two hours in a 2° twaddle solution of 

 bleaching powder, containing 5.82 grams of chlorine per liter, rinsed 

 with cold water, soured with 2 per cent solution of acetic acid, 

 rinsed and antichlorecl in a 2 per cent solution of sodium bisulphite 

 30 minutes, then finally rinsed and blued in water containing 1 gram 

 of vat blue in each 13^ liters. 



Method B. Treated as in method A, except that a solution of elec- 

 trolized salt containing 2.87 grams per liter of available chlorine 

 was used as the bleaching agent. 



The tensile strength and the number of the yarn of all four samples 

 were taken before and after treatment with bleach A and bleach B 

 with the results as shown in Table VII. 



Table YII. — Tensile strength of yarns before and after bleachmg. 





Grey. 



Bleach A. 



Bleach B. 



Sample 

 No. 



No. of 

 yam. 



Skein 

 breakage, 

 60 yards. 



Single- 

 thread 

 breakage. 



No. of 

 yarn. 



Skein 

 breakage, 

 60 yards. 



Sijigle- 



tliread 



breakage. 



No. of 

 yarn. 



Skein 

 breakage, 

 60 yards. 



Single- 

 thread 

 breakage. 



1 



26.4 

 26.4 

 41.5 

 41.0 



44.8 

 45.7 

 42.4 

 43.2 



10.9 

 10.9 

 9.8 

 9.8 



29.2 

 29.2 

 47.2 

 47.2 



36.8 

 39.4 

 27.7 

 29.3 



8.7 

 8.9 

 7.9 

 8.0 



29.4 

 29.4 

 46.5 

 46.5 



44.1 

 43.8 

 34.6 

 39.0 



10.4 



la 



9.7 



2 



8.9 



2a 



9.1 







In this table the tensile strength ^ is given in pounds for the skein 

 breaks aiid in ounces for the single-thread breaks. The skeins were 

 taken from the same bobbins of which the single threads were tested. 

 From the comparisons of these figures it will be seen that the dif- 

 ferences in strength betw^een the fumigated and nonfumigated cotton 

 are so small that it would be unsafe to say that these yarns contained 

 in them any substance such as acids that would reduce the tensile 

 strength of the yarn by releasing the bleaching agent too rapidly. 



DYEING OF YARNS. 



Portions from all of the four samples of j^arns. namely, 1, la, 2, 

 and 2a, were bleached according to method A and method B, except 

 that they were not blued. Instead some of the portions were dyed 

 pink and some were dyed blue with both direct and basic dyes. 



1 See footnote, p. 6. 



