Abstract
Concerning the bleaching of cotton yarn with hypochlorite solution, the effect of some additions to the bleaching liquor was investigated with following conclusions.
(1) As might be expected, conversion of calcium hypochlorite into sodium salt by adding sodium carbonate to the bleaching powder solution showc;d the tendency of increasing the stability of the bleaching liquor, and consequently the bleaching action of the same tended to be retared.
(2) Addition of sodium bicarbonate to the bleaching powder solution enhanced the bleaching action.
(3) The bleaching efficiency was promoted by the addition of a suitable amount of such acid as sulphuric, hydrochloric, oxalic or acetic acid, and the rates of increase in bleaching efficiency were the same irrespective of the acid used if an equivalent amount of acid (25cc of N/10 acid in 100cc of bleaching powder solution containing 0.3g of available chlorine) was added
(4) With regard to the strength and elongation of cotton yarn, the bleaching liquor activated by the addition of bicarbonate or acids showed, as expected, unfavourable result when compared to ordinary bleaching liquor. If cotton yarn is steeped in the so called activated bleaching liquor for more than two hours, a marked weakening of the fibre occurs, but as the bleach will be complete within one hour, this method of working can be applied without giving appreciable damage to cotton.
