SALTS OF ALBUMIN AND ACIDS 79 



concentration of acid which produces precipitation, is com- 

 pared with the viscosity. It increases with increasing viscosity 

 (i.e., hydration). These results become comprehensible if the 

 precipitation of the acid albumin by excess of acid is considered 

 as the action of the common ion of the acid, in the same way 

 that common salt is precipitated by hydrochloric acid. In 

 this way an excess of dissociated acid is required to precipitate 

 the acid protein, which is the greater when the number of 

 neutral particles is less, and when they are heavily hydrated. 

 This conception makes the precipitation of albumin in high 

 acid concentrations intelligible as a displacement of the albu- 

 min salt from solution. The completeness of the precipitation, 

 the varied behaviour with excess of acid, etc., are, however, 

 secondary effects which depend on the acid used, and will not 

 be further entered into at this point. 



