104 



OSMOTIC PRESSURE AND VISCOSITY 



during the viscosity measurements the temperature of the solutions 

 was 20° C. 



A biore exact demonstration of the inhibiting influence of acid on 

 the increase of viscosity of gelatin solutions on standing is given in 



LO 15 EO 25 30 35 40 45 50 55 60 



Time in minutes 



Fig. 5. Increase of viscosity of gelatin sulfate solution of different pH on 

 standing. The increase is most rapid at the isoelectric point, thus proving that 

 the acid retards or prevents the formation of submicroscopic sohd particles of 

 jelly on standing. 



Fig. 5. Gelatin sulfate solutions containing 2 gm. of originally 

 isoelectric gelatin in 100 cc. were prepared and heated rapidly to 

 45°C. and cooled rapidly to 20°C., and then kept constantly at 20°C. 



