THE STABILITY OF PROTEIN SOLUTIONS 



249 



the dry weight of gelatin dissolved in a certain time at different 

 pH. This corroborates the conclusion that the solution (and 

 precipitation) of gelatin in water is not influenced by forces 

 governed by the Donnan equilibrium and does therefore not 

 show the characteristics of colloidal behavior. We are probably 

 dealing in this case with forces of residual valency between water 



Influence of salts on 



solution time of 0.6 % 



Na gelatinate pH 10.5 



at 35 C. 



Concentration of salts 



Fio. 75. Influence of salts on solution time of 0.8 gm. of powdered Na gelatinate 

 in 100 c.c. salt solution at pH 10.5. 



and gelatin molecules, these forces being increased, as a rule, by 

 the addition of salt to water, with the exception of the sulphates, 

 which diminish the forces when added beyond a certain concen- 

 tration at which the chlorides do not cause a diminution in 

 solubility. This explains why it is easier to salt out gelatin 

 from its aqueous solutions by sulphates than by chlorides. 



