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



for possible evidence of structure. The experiment was then 

 repeated, taking in this case a solution but a few degrees 

 below the boiling point noted in the first experiment. When 

 the salt solution is obtained of the right concentration for 

 dissolving the cellulose, solution of the cellulose may be 

 obtained in most cases below the boiling point of the salt 

 solution, but in all cases, in order to obtain complete solution 

 by this method it is necessary to heat the mixture to a 

 minimum temperature varying between 90 — 133 C, depend- 

 ing on the particular salt solution used. With pure neutral 

 calcium thiocyanate solution boiling at 133 C, solution of 

 the chemical wood pulp may be obtained by heating to 90 C. 



This work resulted in the discovery that concentrated 

 solutions of the calcium, strontium, magnesium, manganese, 

 and lithium thiocyanate were each solvents for cellulose when 

 heated. 



On careful examination of the solutions of those salts 

 which dissolved cellulose it was noticed that in each case the 

 solution of sufficient concentration to dissolve cellulose was 

 abnormally viscous, a property shared by zinc chloride 

 solution, which has long been known to be a cellulose solvent. 



This idea of a possible relationship between the viscosity 

 of a salt solution and its solvent action on cellulose was 

 submitted to critical examination, and the viscosities of the 

 solutions of a number of thiocyanates were determined at 

 different concentrations, at constant temperature, by means of 

 the Ostwald viscometer. 



These results showed that as the concentration increased 

 the viscosities of the solutions of the calcium, strontium, 

 magnesium, manganese, lithium, and aluminium thiocyanates 

 rapidly increased, whereas the solutions of the potassium, 

 sodium, ammonium, nickel, and zinc thiocyanates increased 

 but slowly ; the former group being much more viscous than 

 the latter for equal molecular concentrations. 



Now the concentrated solutions of the calcium, strontium, 

 magnesium, manganese, and lithium thiocyanates had been 

 found in the course of this work to be solvents for cellulose, 

 but no solution of the cellulose was obtained with the 

 aluminium thiocyanate solution, although the viscosity of its 

 concentrated solution was high. With the thiocyanate solu- 

 tions of low viscosity such as those of potassium, sodium, etc., 

 no solution of the cellulose was obtained at any concentration. 

 With the one exception then of the aluminium salt, the high 

 viscosity very sharply differentiates those aqueous solutions 

 which dissolve cellulose from the non-solvent solutions of low 



