210 



THEORY OF COLLOIDAL BEHAVIOR 



pH of the gelatin varied in the neighborhood of 3.0; the. tempera- 

 ture was 20C. After 2J hours, when the Donnan equilibrium 

 between the particles and the surrounding solution was supposed 

 to be established, the viscosity of each suspension was measured 

 at 20C. and the volume occupied by the suspended particles of 

 gelatin was ascertained in the manner described. It was found 



S 

 Id 





2048 1024 512 256 128 64 32 16 



Concentration ofNaN0 3 



FIG. 55. Showing depressing influence of neutral salts on viscosity of sus- 

 pensions of powdered gelatin in water and on the volume occupied by the gelatin 

 particles in the suspension. 



that the addition of salt diminished the relative volume of the 

 gelatin particles and the viscosity (Fig. 55) . Where the volume 

 of the gelatin was great it no longer varied parallel with the 

 viscosity, as was to be expected from the fact that Einstein's 

 formula no longer holds in this case. 



The measurements of the pH of the gelatin solution and the 

 outside solution showed that the addition of salt diminished the 

 difference between the two, as Donnan's theory demands (Table 

 XLII). 



