JACQUES LOEB 



561 



TABLE II. 

 pH Inside Minus pH Outside after 18 Hours. 



Original inside solution, 1 per cent originally isoelectric gelatin dissolved in 

 various concentrations of NaNOa made up with HCl to pH 3.5. 



Outside solution, same concentrations of NaNOs all made up with HCI to 

 pH 3.0. 



TABLE III. 



Potential Difference between Gelatin Solution and Outside Solution. 



IV. 



The greatest puzzle in the physical chemistry of the proteins is the 

 fact that at the isoelectric point of gelatin and crystalline egg albumin 

 the osmotic pressure is a minimum, that it rises when acid is added, at 

 first with the increase of acid added, reaching a maximum when the 

 pH is about 3.5, and that on further addition of acid a rapid fall of 

 osmotic pressure occurs. 



It was also reported in the preceding papers that the osmotic pres- 

 sure of gelatin chloride and gelatin phosphate solutions of the same 

 pH and the same concentration of originally isoelectric gelatin was 

 about the same, that the osmotic pressure of gelatin oxalate was slightly 



