254 ■ AMPHOTERIC COLLOIDS. II 



ion concentration increases the water solubility of gelatin near the 

 isoelectric point, no increase in the solubility can be produced by 

 treating gelatin at the isoelectric point with any other kind of mono- 

 valent or polyvalent ion; a fact apparently not in harmony with the 

 adsorption theory of colloids, but in harmony with a chemical concep- 

 tion of proteins. 



The writer wishes to express his thanks to Mr. M. Kunitz for his 

 faithful assistance in these experiments. 



