74 



DONNAN EQUILIBRIUM AND VISCOSITY 



viscosity curves in Fig. 1 of this paper since the relative volume of 

 gelatin sulfate was found to be not far from one-half of that of gelatin 

 chloride or gelatin phosphate of the same pH. This demonstration 

 completes the proof that the viscosity of suspensions of powdered 

 gelatin in water of different pH is influenced in the same way by 



pH 16 16 E.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4 3.6 3.8 4.0 4.2 44 4.6 



Fig. 1. Viscosity of suspensions of 0.5 gm. of powdered gelatin of grain size 

 100 to 120. Abscissae are the pH, the ordinates the ratio of time of outflow of 

 suspension: time of outflow of water. The influence of HCI and H3PO4 is practic- 

 ally identical for the same pH while H2SO4 depresses the viscosity of the suspen- 

 sions to a litth less than one-half of that for HCI. 



electrolytes as is the viscosity of solutions of the same gelatin salts, 

 and that this influence is due, in the case of suspensions, to the in- 

 fluence of the Donnan equilibrium upon the swelling of the particles. 



The volume V of gelatin occupied in 100 cc. of the suspension was 

 determined by filtering and deducting the volume of the filtrate 



