30 Cellulose 



product is especially interesting, as the first instance of the 

 synthesis of a soluble cellulose derivative i.e. soluble in 

 water by a reaction characteristic of the alcohols generally. 

 The actual dissolution of the cellulose under this reaction we 

 cannot attempt to explain, so long as our views of the general 

 phenomena of solution are still only hypotheses. There is 

 this feature, however, common to all the processes hitherto 

 described, for producing an aqueous solution of cellulose (i.e. 

 a cellulose derivative), viz. that the solvent has a saline cha- 

 racter. It appears, in fact, that cellulose yields only under the 

 simultaneous strain of acid and basic groups, and therefore we 

 may assume that the OH groups in cellulose are of similarly 

 opposite function. In the case of the zinc chloride solvents 

 there cannot be any other determining cause, and the soluble 

 products may be regarded as analogous to the double salts. 

 The retention of the zinc oxide by the cellulose, when pre- 

 cipitated by water, is an additional evidence of the presence of 

 negative or acidic OH groups ; and, conversely, the much more 

 rapid action of the zinc chloride in presence of hydrochloric 

 acid indicates the basicity of the molecule, i.e. of certain of 

 its OH groups. On the other hand, in both the cuprarn- 

 monium and thiocarbonate processes there may be a disturbance 

 of the oxygen-equilibrium of the molecule ; and, although there 

 is no evidence that the cellulose regenerated from these 

 solutions respectively is oxidised in the one case, or deoxidised 

 in the other, it is quite possible that temporary migration of 

 oxygen or hydrogen might be determined, and contribute to 

 the hydration and ultimate solution of the cellulose. But, 

 apart from hypotheses, we may lay stress on the fact that these 

 processes have the common feature of attacking the cellulose 

 in the two directions corresponding with those of electrolytic 

 strain ; and it is on many grounds probable that the connection 

 will prove to be causal and not merely incidental 



