54 Cellulose 



These changes are marked by a shrinkage in linear dimen- 

 sions of about T Vth : the tensile strength of the paper thus 

 treated is about ten times that of the original. (J. Chem. Soc. 

 47, 183.) 



(3) Hydrochloric acid, both in the form of gas and con- 

 centrated aqueous solution, rapidly disintegrates cellulose 

 tissues. The product, obtained from cotton, after washing and 

 drying, is a white powder which under the microscope is seen 

 to consist of angular fragments of the original fibres. It has 

 been termed hydrocellulose by Girard, who first described this 

 product, and hydracellulose (Witz), the latter term being, per- 

 haps, preferable. According to Girard, the product may be 

 represented as ^C^H^On) as having, i.e. the same em- 

 pirical composition as the above-described amyloid. From 

 cellulose it also differs similarly to the latter, in the presence of 

 free CO groups and the greater reactivity of its OH groups. 

 Thus it reacts with acetic anhydride at its boiling point ; the 

 acetylation, however, does not proceed very far. 



The product is dissolved by nitric acid (1*5 sp.gr.) without 

 oxidation, and from the solution a series of nitrates are obtained : 

 (i) the lowest nitrates, by spontaneous evaporation of the solu- 

 tion in their fibres ; (2) higher nitrates, by precipitation with 

 water ; and (3) the highest nitrates, by precipitation with sul- 

 phuric acid. 



From these properties it may be concluded that, in general 

 molecular configuration, these derivatives are similar to cellulose, 

 but are so modified that the typical reactions take place under 

 much less extreme conditions. 



The action of this acid we should expect to be one of 

 dehydration ; and, although the final product has the composition 

 of a hydrate, there is every reason to regard the hydration as 

 a secondary result, following the molecular rearrangement 

 caused by the initial dehydration. 



