The Typical Cellulose and the Cellulose Group 21 



these products of the hydrolysis being susceptible of ' conden- 

 sations,' in which the reverse action is determined. On the 

 other hand, it has been recently shown (Wohl) that the con- 

 ditions may be so chosen as to exclude the latter, viz. by ope- 

 rating in the cold and in presence of a minimum of water, in 

 which case we get the surprising result that the hydrolysis of 

 the sugar is determined by -5-^ p.ct. of its weight of HC1. 



Applying these considerations to the case of the more 

 complex cellulose molecule it is easy to see that it may undergo 

 a series of hydration changes, with attendant resolutions, with- 

 out any change of its empirical formula. The disintegrating 

 action of the dilute acids appears to be of this kind. 



The action of the aqueous acids upon cellulose has been investi- 

 gated by various observers, amongst others by Grace Calvert, 

 Girard (Compt. Rend. 81, 1105), C. Koechlin (Bull. Mulhouse, 

 1888). The latter observer gives the results of a study of the 

 limiting conditions of action of aqueous sulphuric acid at various 

 degrees of concentration. What may be called the critical con- 

 centration of the acid lies between the limits of 60-80 B. Thus 

 with the mixture of 3 vols. of concentrated acid and 8 vols. water 

 i.e. an acid of 69 B. at the ordinary temperature, its action 

 upon cotton does not become evident until after three hours' 

 exposure. With an aqueous acid containing loo grms. H 2 SO 4 per 

 litre and at 80 C. the first appearances of change in the cotton are 

 noticed at the expiration of five minutes ; after thirty minutes' 

 exposure there is sensible disintegration ; and the completion of 

 the action, i.e. conversion into a friable mass of hydrocellulose, 

 requires an exposure of 60 minutes' duration. 



To alkaline solutions at high temperatures, cotton cellulose 

 is, on the other hand, very resistant. Solutions of caustic soda 

 of 1-2 p.ct. Na 2 O are without sensible action upon cotton 

 at temperatures considerably over 100. The principal opera- 

 tions in the process of bleaching cotton and linen textiles con- 

 sist in drastic alkaline treatments of this kind, whereby the 

 1 non-cellulose ' constituents of the fibre are for the most part 



