EDWIN JOSEPH COHN 



717 



Although solubility data suggested that no appreciable free electrolyte 

 was present in these preparations, their ash contents were considerable. 

 The ash constituted 0.7 per cent of preparation IV. In prepa- 

 ration V more careful methods of purification and precipitation 

 reduced the ash to 0.3 per cent. 



The Solubility of Tuberin. 



The measurements upon tuberin, although they have been made 

 on but one preparation, and although they are not nearly so accurate 



TABLE V. 



Solubility of Tuberin I. 



T. = 25.0°±0.1°C. 



* 5 cc. sample used. 



as those that have been presented for serum globulin, or those that 

 will be recorded for casein, are included for two reasons. In the first 

 place because they establish the approximate constancy of solubility 

 of another globulin derived from an entirely different source; in the 

 second place because a study of ''the relation between the isoelectric 

 point of a globulin (tuberin) and its solubility and acid combining 

 capacity in salt solution" (14) was responsible for the inception of 

 these studies. The data obtained at that time showed the effect of 

 even a uni-univalent salt, sodium chloride, in shifting the minimum 

 of protein solubility. This phenomenon has already been discussed. 



