JACQUES LOEB 371 



5. Measurements of the pH inside the powdered particles and of the 

 pH in the outside watery solution show that when equilibrium is 

 established the value pH inside minus pH outside is positive when 

 the powdered particles contain a gelatin-acid salt, while the value 

 pH inside minus pH outside is negative when the powdered particles 

 contain Na gelatinate. At the isoelectric point the value pH inside 

 minus pH outside is zero. 



6. The addition of neutral salts depresses the electrical charge of 

 the powdered particles of protein-acid salts. It is shown that the 

 addition of salts to a suspension of powdered particles of gelatin 

 chloride also diminishes the value of pH inside minus pH outside. 



7. The agreement between the values 58 (pH inside minus pH 

 outside) and the p. d. observed by the Compton electrometer is not 

 only qualitative but quantitative. This proves that the difference 

 in the concentration of acid (or alkali, as the case may be) in the two 

 phases is the only cause for the observed p.d. 



8. The Donnan theory demands that the p.d. of a gelatin chloride 

 solution should be 1| times as great as the p.d. of a gelatin sulfate 

 solution of the same pH and the same concentration (1 per cent) of 

 originally isoelectric gelatin. This is found to be correct and it is 

 also shown that the values of pH inside minus pH outside for the two 

 solutions possess the ratio of 3:2. 



9. All these measurements prove that the electrical charges of 

 suspended particles of protein are determined exclusively by the 

 Donnan equilibrium. 



