Experimental and Applied 287 



obtained by a light alkaline boil, followed by a treatment with 

 bleaching liquor (hypochlorite), these treatments being once or 

 twice repeated for higher grades of bleaching. The consump- 

 tion of bleaching powder is relatively large (10-30 p.ct. of the 

 weight of the goods), a considerable proportion being used up 

 in oxidations which do not contribute to the bleaching effect 

 proper. The processes are therefore not economical in the 

 strict sense of the term, and are capable of considerable 

 improvement in the direction of a more specific attack of the 

 coloured constituents of the yarn. In various grades of paper 

 making, also, similar half-bleaches are practised. 



Jute (cuttings and waste) is boiled in lime and bleached 

 with bleaching powder solution, the resulting pulp being of a 

 yellow to a yellowish-white colour, still retaining a large pro- 

 portion of the non-cellulose constituents of the original fibre, 

 and giving all its characteristic reactions. Flax wastes (scutch- 

 ing tow) are boiled with lime or soda to soften and disintegrate 

 the residues of wood (sprit), and the pulp is bleached with 

 hypochlorites. 



The principle of these treatments is, however, one and the 

 same for all, and is sufficiently illustrated by the examples 

 discussed. 



(b) The second group of bleaching processes, of which the 

 goal is a pure cellulose (or oxycellulose), differ from the above 

 in this general and important particular : the chemical work is 

 thrown chiefly on the alkaline boiling processes, the bleaching 

 treatment proper being limited to the oxidation of the coloured 

 residues from these treatments. Thus in cotton bleaching, while 

 the consumption of caustic soda may be taken at 80-100 Ib. 

 per ton of cotton goods, the bleaching powder required is 

 less than 30 Ib. per ton, a proportion of which is wasted in the 

 unavoidable losses attending the washing away of residual 

 liquors. In both cotton and linen bleaching of this order, 



