Experimental and Applied 285 



by the electrolysis of solutions of the chlorides (chiefly MgCl 2 ) 

 are also now extensively used (Hermite process). 



Chemically, therefore, the bleaching processes of the arts 

 consist essentially of the two treatments : (i) alkaline hydrolysis 

 followed by (2) alkaline oxidations. 



In the processes of the first group the alkaline treatments 

 are of the milder order, the purpose being to dissolve and 

 remove the minimum of non-cellulose constituents, consistently 

 with obtaining a uniform and sufficiently high colour (bleach) 

 in the finished product. As therefore a large proportion of the 

 more oxidisable (non-cellulose) constituents is retained in the 

 pulp or fabric, the consumption of the bleaching agent in the 

 after process is relatively high. It is in fact used up, not in 

 selectively oxidising those constituents which are the colouring 

 matters of the alkali-boiled fibre or fabric, but obviously in 

 a general oxidation of the non-cellulose constituents in the 

 order of oxidability. 



Two processes may be considered as typical of this group : 



(i) Jute fabrics and jute pulp. Jute itself may be whitened 

 considerably by regulated oxidations. In the case of this fibre, 

 however, it is difficult to control the action of bleaching 

 powder. The avidity of the lignocellulose for chlorine is such 

 that should any free hypochlorous acid be formed in the solu- 

 tion, chlorination of the fibre immediately results. The pre- 

 sence of the lignone chlorides in the fibre is a source of con- 

 siderable danger. Being unstable they are gradually decom- 

 posed, with liberation of hydrochloric acid, which rapidly 

 disintegrates the fabric. The neglect of this property of the 

 lignocellulose has led to disastrous consequences in manufac- 

 ture. An industry established some years ago for the bleaching 

 and printing of jute cloth was ruined through the wholesale 

 ' tendering' of the goods from this cause. The process 

 adopted consisted in (a) boiling in weak alkaline solutions 



