JACQUES LOEB 671 



3. The reversal seems to be due to or to be accompanied in both 

 cases by a chemical change in the protein. The chemical change 

 which occurs when the hydrogen ions reverse the sign of charge of the 

 protein film consists in the formation of a protein-acid salt whereby 

 the H ion becomes part of a complex protein cation; while the chemical 

 change which occurs when trivalent cations reverse the sign of charge 

 of the protein film consists in the formation of an insoluble and 

 therefore sparingly or non-ionizable metal proteinate. 



