650 



STABILITY OF BACTERIAL SUSPENSIONS. II 



less effective in reducing the cohesive force. The agglutination de- 

 pends on both factors. It is possible, therefore, for all monovalent 

 ions to affect the potential in the same way but to differ in their 

 coagulating power. In order to predict the coagulating efl&ciency of 

 a salt, it is therefore necessary to know the effect on both the poten- 

 tial and cohesion. 



Sedt concentration, equivalents per liter 



Fig. 9. Effect of salts and acids on the cohesive force between films of 

 B. typhosus. 



The HCl curve differs from the others in that the cohesion is in- 

 creased in solutions of higher concentration than 0.3 N. This agrees 

 with the agglutination test (Fig. 3) which shows a zone of agglutina- 

 tion at this concentration. 



The experiments show the result usually obtained in such cases, 

 that low concentrations of salt precipitate and higher concentrations 

 stabilize again. They also show that this is due in most cases to the 



