202 Cellulose 



(3) With regard to the mechanism of the reaction in the 

 original resolution of the lignocellulose, it is of a complex 

 character ; and the synthetic equilibrium of the products in 

 the resulting solution is, no doubt, different from that repre- 

 sented by the parent complex. We may very well assume 

 that the reaction involves the following factors : (a) the hydro- 

 lytic action of the sulphurous acid ; (b) the formation of 

 aldehyde bisulphite compounds ; (c) the probable sulphona- 

 tion of side chains of the general form #.CH : CH.COH, 

 as in the well-known reaction of cinnamic aldehyde with 

 sodium bisulphite ; (d) the saturation of acid OH groups 

 by CaO. 



These researches are, it will be seen, an important prelimi- 

 nary elucidation of the problem of the composition of this 

 interesting industrial product, and afford general conclusions 

 as to the constitution of the non-cellulose constituents of the 

 lignocelluloses, which entirely confirm the deductions given in 

 preceding sections of this treatise. 



In regard to the pulp or insoluble product of the original 

 reaction, which is, as already stated, an industrial product of 

 the greatest importance, it represents the cellulose of the wood 

 together with residues of the non-cellulose in small proportion, 

 not removed by the treatment. The presence of the latter is 

 marked by the colour of the product, which is usually a greyish- 

 pink. A large quantity of the pulp is used in this crude or 

 unbleached condition ; but for white papers a preliminary 

 treatment with bleaching powder is practised, the proportion 

 required being from 15-25 p.ct. of the weight of the pulp. 

 The process is attended by a loss of weight of from 8-12 p.ct, 

 owing to conversion of the more oxidisable constituents of the 

 pulp into soluble derivatives. 



It is to be noted that the yield of bleached cellulose by this 

 process is, as in many other cases, considerably inferior to that 



