ALBUMENS AND OTHER ORGANIC SUBSTANCES. CREIGHTON. 73 



ferrous, as well as ferric salts, adsorbed by albumen and 

 gelatine. That this is not the case at once suggests that the 

 selective adsorption of trivalent iron may be due to some 

 electrical effect. In support of this it may be mentioned it has 

 recently^ been pointed out, that while the adsorption of non- 

 electrolytes is probably due to surface tension phenomena, that 

 of electrolytes is probably of electrical origin. 



Additional evidence of the adsorption of ferric compounds 

 by native and derived proteins is afforded by the fact that the 

 coagulation temperature of albumen is increased by these sub- 

 stances. This behaviour is in accordance with that observed by 

 Pauli and HandovsJcy^ , who found that small concentrations of 

 alkali salts retarded the coagulation of albumen, i. e. raised 

 the coagulation temperature. 



The supposition of the formation of a chemical compound 

 is supported by the raising of the coagulation temperature of 

 albumen when trivalent iron is present; by the disappearance 

 of the colour of soluble Prussian blue on the addition of 

 albumen or gelatine to its solution; and by the fact that the 

 rate of fading of the blue colour increases as the temj^erature 

 of the solution is raised. This last is a further argiuxitnt 

 against the hindering of the reactions being brought about by 

 the protein lessening the degree of dissociation of the iron com- 

 pounds. The fact that hydrochloric acid when added to mix- 

 tures of potassium ferricyanide and albumen or gelatine, such as 

 used in the foregoing experiments, liberates the ferricyanide 

 ■so that it is demonstrable by ammonium ferrous sulphate and, 

 in the case of albumen mixtures, also precipitates the albumen ; 

 the return of the blue colour to solutions of soluble Prussian 

 blue that have been decolorized with gelatine, on the addition 

 of hydrochloric acid, hydrogen peroxide, or on exposure to 



1. Lachs, H. and L. Michaelis : Zeitschr. Elektrochem., 17,1,(1911); ibid. 17, 917 

 (1911). 



2 Pauli, W. and H. Handav-sky : Bjitrage z. cbem. Physiol, u. Pathol 11 

 415, (1908). 



