12 H. E. Williams — Action of Neutral Salts on Cellulose 



definite hydrate in solution, but that the solution must be so 

 concentrated that it is capable of combining with more water ; 

 the solution therefore at least in the cold must consist of a 

 liquid hydrate. 



As an aqueous salt solution having the necessary viscosity 

 and boiling- point, but which is not hydrated or only partially 

 hydrated in solution, and therefore contains free water, is a 

 non-solvent for cellulose, it is evident that the combined 

 water plays an important part in the solution of the cellulose, 

 the solution being brought about by means of the combined 

 water, or the capacity of the salt for taking up water. The 

 combination of the salt and water must, however, be of a 

 certain order, that is to say the water must be bound to the 

 salt between the limits of a maximum and minimum intensity, 

 above or below which no solution of the cellulose can take 

 place on heating. 



A simple and possible explanation of the solvent action on 

 cellulose of these salt solutions, which fulfils the prescribed 

 conditions, may be stated thus : — The hydroxyl groups of the 

 cellulose unit link up with the salt complex in place of the 

 water molecules, acting in the manner of a substituted water 

 group, thus causing the fibre to swell considerably. The 

 cellulose unit is brought by this means into molecular range 

 with the water molecules combined with the salt. By raising 

 the temperature the union between the salt and water mole- 

 cules will weaken and tend to part from the parent molecule. 

 The water thus freed migrates to the cellulose by which it is 

 imbibed, causing further swelling of the fibre, which increases 

 as the progressive hydration proceeds. The highly swollen 

 fibre in the gelatinous condition then peptises, and passes 

 into colloidal solution. 



The temperature of the solution would in the first place 

 tend to weaken the union of the cellulose aggregate, and in 

 the second place tend to dissociate the salt hydrate complex. 



The minimum temperature of the boiling point of the 

 solution is probably not a direct function of the solvent 

 action, but, as it has been shown above that in the liquid 

 hydrate required the water must be bound to the salt between 

 the limits of a maximum and minimum intensity, it is 

 probable that the latter would occur at the same boiling point 

 with various solutes. 



The explanation of the mechanism of the entrance of the 

 cellulose into the salt hydrate complex, by means of its 

 hydroxyl groups taking the place of the water, has some other 

 facts to support it. Thus ethyl ether which may be con- 



