120 



CHEMICAL STATICS 



The valency of the coagulating ion would appear to be quanti- 

 tatively of less importance in the coagulation of proteins by 

 salts than it is in the precipitation of ionic protein by small 

 quantities of salts, since magnesium resembles the alkalies closely 

 in its coagulative power, while lithium approaches the alkaline 

 earths. 



The order of effectiveness of the different salts in bringing 

 about the coagulation of electropositive protein is, however, exactly 

 the reverse of their order of effectiveness in bringing about the 

 coagulation of electronegative protein, such as the albumin in egg- 

 white. This was first shown by Posternak (64), who employed 

 the reserve-material of the seeds of Picea excelsa, dissolved in 

 very dilute hydrochloric acid. Posternak's observation has been 

 confirmed by Pauli (53) and by Hoeber (29). Acidifying a 

 solution of egg-white reverses the functions of the coagulating 

 ions, those which coagulated electronegative protein most strongly 

 now inhibit its coagulation most strongly. Those which inhibited 

 its coagulation now induce coagulation. The series is reversed 

 in every respect; the anions now induce coagulation and the 

 cations inhibit it. The anions precipitate in the order: 



CNS > I > Br > NO 3 > Cl > Acetate, 

 while the cations inhibit precipitation in the order: 

 Li > Na > K > NH 4 > Mg. 



When electronegative protein (egg-white) is acted upon by 

 salts of the alkaline earths "irreversible" precipitates or coagula 



