18 THEORY OF COLLOIDAL BEHAVIOR 



The idea that the viscosity of protein solution depends primarily 

 upon the protein ion was accepted by W. Pauli, 1 who made the 

 additional hypothesis that each protein ion is hydrated; i.e., 

 that each individual protein ion is surrounded by a considerable 

 shell of water. Pauli worked with blood albumin which had 

 been freed from salts by a dialysis continued for several weeks. 

 When he added acid to water-soluble albumin, the viscosity 

 increased first from 1.0623 for the pure albumin solution to 

 1.2937 when the concentration of HC1 added to the albumin 

 solution was 0.017 N. When the HC1 concentration was in- 

 creased to 0.05 N the viscosity was only 1.1667. The following 

 figures give the data according to Pauli: 



Concentration of HC1 0.0 N 0.005 N 0.01 N 0.012 N 0.017 N 0.02 N 0.03 N 0.04 N 0.05 N 

 Viscosity 1.06231.2555 1.233 1.274 1.2937 1.27701.2241.18221.1667 



Pauli assumed that the protein ions are surrounded by a jacket 

 of water, while the non-ionized molecules of protein he assumed 

 not to be hydrated. Addition of a little HC1 to isoelectric 

 albumin would cause the transformation of non-ionized albumin 

 into albumin chloride which is highly ionized and hence assumed 

 to be highly hydrated; the more acid is added the more albumin 

 chloride and the more hydrated albumin ions should be formed. 

 Hence, the viscosity should at first increase with the quantity 

 of acid added, until a point is reached where the addition of more 

 acid represses the degree of electrolytic dissociation of the albu- 

 min chloride on account of the high concentration of the Cl ion 

 common to both protein chloride and HC1. 



If we intend to use these ideas for the explanation of the influ- 

 ence of the valency of ions on the physical properties of proteins 

 we are compelled to assume that the degree of electrolytic 

 dissociation of gelatin salts with bivalent ions is lower than that 

 of gelatin salts with monovalent ions. Since, e.g., the viscosity 

 of gelatin chloride solutions is considerably higher than thie 

 viscosity of gelatin sulphate solutions of the same hydrogen ion 

 concentration and the same concentration of originally iso- 

 electric gelatin, we should have to conclude that the degree of 

 electrolytic dissociation of gelatin sulphate is considerably less 

 than that of gelatin chloride. 



1 PAULI, W., Fortschr. naturwiss. Forschung, vol. 4, p. 223, 1912; "Kol- 

 loidchemie der Eiweisskorper," Dresden and Leipsic, 1920. 



