JACQXJES LOEB 761 



solution can, however, only be established when the particles contain 

 protein ions. 



There exists a criterion which seems to permit us to decide which one 

 of the two types of forces is responsible for the stability of a solution 

 or suspension. When the stability depends upon the repulsive forces 

 due to a potential difference between micellae and solution, com- 

 paratively low concentrations of solutions will be required for the 

 precipitation of the protein, since comparatively low concentrations 

 of salts {e.g. concentrations of m/8 or less) suffice for the annihilation 

 of the p.D. When, however, the stability of a solution is not deter- 

 mined by the p.d. between micellae and solution but by forces of 

 residual valency between molecules of solute and solvent, much higher 

 concentrations of salts are, as a rule, required for precipitation than 

 are sufficient for the annihilation of a p.d. caused by the Donnan 

 equilibrium. Moreover, the efficiency of a salt in annihilating the 

 P.D. between a micella and a solution is the lower the higher the 

 valency of that ion of the salt which has the opposite sign of charge 

 to that of the micella. 



n. 



The Prevention of Heat Coagulation of Isoelectric Egg Albumin by 

 Trivalent and Tetravalent Ions. 



Isoelectric crystalline egg albumin is quite soluble in water as long 

 as the temperature is low. 8 per cent solutions kept at 2°C. remained 

 perfectly clear for more than a year — and they would probably have 

 kept clear indefinitely. Since it requires very high concentrations 

 of salts to cause a precipitation of isoelectric crystalline egg albumin 

 from aqueous solution at ordinary temperature, we may assume that 

 the forces determining the stability of solutions of isoelectric crystal- 

 line egg albumin at sufficiently low temperature are not the electrical 

 charges of micellae but the attraction between molecules of isoelectric 

 albumin and molecules of water. When, however, the temperature 

 of a 1 per cent solution of isoelectric crystalline egg albumin is raised 

 to about 73°C. or above, crystalline egg albumin is flocculated. 

 Through the rise in temperature a change occurs in the molecule of 

 crystalline egg albumin, whereby the attraction of the molecules of 



