PROTEINS 



149 



The ability to decrease the solubility of easily soluble electrolytes 

 and to increase the solubility of difficultly soluble electrolytes is not 

 a specific property of albumins but is common to colloids in general, 

 e.g., gelatin. 



Albumin and Hydrosols. The exhaustive studies of U. FRIEDE- 

 MANN* show that electrolyte-free serum and egg albumin are pre- 

 cipitated both by positive and negative inorganic hydrosols. An 

 optimum precipitation zone exists here, as it does in other colloid 

 precipitations. Excess of albumin or inorganic hydrosol hinders the 

 precipitation. Addition of NaCl shifts the zone of precipitation 

 without, however, conforming to any definite law. As an example 

 I might mention the precipitation ( X X X ) of albumin by diminish- 

 ing quantities of molybdic acid, with and without added NaCl. 



As the result of cataphoretic experiments, U. FRIEDEMANN be- 

 lieves that the charge of proteins towards water is not determinative 

 of their precipitation by inorganic hydrosols. Albumin which 

 travels to the anode, notwithstanding this fact gives heavy pre- 

 cipitates with inorganic hydrosols (arsenic trisulphid, silicic acid, 

 molybdic acid). There is much to justify the assumption of U. 

 FRIEDEMANN that a given hydrosol, according to its charge, collects 

 at the + or charge of the amphoteric albumin, thus permitting 

 its aggregation to larger complexes. 



The albumins appear to act with proteins of definite basic (histones) 

 or acid character just as they do with inorganic hydrosols (U. FRIEDE- 

 MANN and H. F.RIEDENTHAL*). 



Influence of Electrolytes. 



If an electrolyte is added to an amphoteric albumin, the properties 

 of the albumin undergo considerable modification. Salts, even in 

 very small quantities (hundredth normal), raise the coagulation tem- 

 perature, as is shown in the subsequent coagulation temperatures 

 taken from a table compiled by Wo. PAULI and H. HANDOVSKY.* 1 



