148 Cellulose 



neutral solution is the oxide MnO 2 , which is deposited upon, 

 and in intimate combination with, the lignocellulose. If re- 

 moved by treatment with sulphurous acid it does not further 

 attack the lignocellulose, the treatment merely revealing the 

 bleaching action accomplished in this stage of the deoxidation. 

 By treatment with sulphuric acid the lignocellulose under- 

 goes further oxidation, and with hydrochloric acid chlorine is 

 liberated and combines with the fibre-substance. These re- 

 actions are, however, of little importance. The permanganate 

 bleach is too costly for general adoption in the case of jute 

 fabrics. From its simplicity, it is a useful treatment in the 

 laboratory, whether for removing coloured impurities from the 

 raw fibre, or from cellulosic products separated by any of the 

 processes already described. 



Hypochlorites. Bleaching powder solution (calcium hypo- 

 chlorite) and the equivalent sodium compound act, in pre- 

 sence of excess of the base, as oxidising compounds ; but as 

 by oxidation and attendant hydrolysis, acid derivatives are 

 formed from the lignocellulose, the use of a * neutral ' solution 

 of the bleaching solution often leads to chlorination of the 

 fibre-substances, owing to liberation of hypochlorous acid. 

 Neglect of this probability has led to disastrous results in the 

 bleaching of jute piece goods ; and a full discussion of the 

 matter, in both practical and theoretical bearings, will be found 

 in the Bull. Soc. Ind. Mulhouse, 1880. 



The danger is avoided by ensuring the presence of excess 

 of base ; this is more easily controlled in solutions of the soda 

 compound, which are therefore to be preferred. After 

 bleaching with the hypochlorites, the fibre or fabric should be 

 well washed, and plunged for a short time into sulphurous acid 

 solution which removes the last traces of oxidising compounds. 

 After again washing, the lignocellulose may be dried without 

 change of colour. 



