VISCOSITY 



221 



These experiments then support the conclusion that the high 

 viscosity of gelatin solutions and the influence of electrolytes on 

 this viscosity is due to the fact that these solutions contain sub- 

 microscopic particles of solid jelly (micellae) capable of occluding 

 large amounts of water the quantity of which is regulated by the 

 Donnan equilibrium. 



4. The pH influences the viscosity of casein chloride solutions 

 in a similar way to that in which it influences gelatin chloride 



pH 1.8 2.0 22 2.4 2.6 2.8 3.0 32 34 3.6 3.8 4.0 42 4.4 4.6 



FIG. 62. Showing that previous heating diminishes the viscosity of 0.5 per cent 

 solutions of gelatin chloride. 



solutions; and the depressing effect of neutral salts on the vis- 

 cosity of casein chloride solutions is similar to that of the addition 

 of salts on the osmotic pressure of gelatin chloride. Casein 

 chloride solutions have no tendency to set to a jelly, but they 

 have one feature in common with gelatin solutions, namely, the 

 existence of particles capable of occluding water, the amount of 

 which is regulated by the Donnan equilibrium. As a conse- 

 quence, casein chloride solutions have a comparatively high 

 viscosity which is influenced by electrolytes in the way charac- 

 teristic for the Donnan equilibrium. The existence of such 



