484 AMPHOTERIC COLLOIDS. IV 



ing, and a high alcohol number, while the gelatin salts with bivalent 

 cations have a milch lower osmotic pressure, lower viscosity, etc. 

 It was also found that the addition of a certain amount of a salt with 

 a bivalent or polyvalent cation depresses the effect of salts with 

 monovalent cation on osmotic pressure, viscosity, swelling, etc., of 

 the gelatin. 



Pauli^ and Michaelis^ seem to ascribe the variations in the swelling 

 and the viscosity of protein solutions to variations in the degree of 

 ionization and to a " hydratation" they assume to be connected with 

 the ionization of the protein. According to this view we should have 

 to assume that sodium gelatinate has a higher osmotic pressure than 

 calcium gelatinate of the same concentration, because the former is 

 more strongly ionized. In an earher paper the writer tentatively 

 accepted Pauli's hypothesis, but a closer scrutiny of the literature 

 showed that neither Pauli nor Michaelis measured the effect of elec- 

 trolytes upon the conductivity of their protein solutions, probably on 

 account of the fact that they did not remove the excess of electrolyte 

 after it had acted on the protein. The writer's method of removing 

 the excess of electrolytes after they have had time to react with the 

 gelatin made measurements of conductivity possible, and these meas- 

 urements in connection with measurements of osmotic pressure and 

 of the quantity of metal in combination with the gelatin led to a very 

 definite explanation of the influence of the valency of ions on the prop- 

 erties of gelatin. With the same equivalent of metal in combination 

 with a given mass of gelatin the maximal osmotic pressure of a 1 per cent 

 solution of gelatin salts with univalent cation, e.g. Na gelatinate, is al- 

 most exactly three times as great as that of gelatin salts with a bivalent 

 metal, e.g. Ca gelatinate, while the conductivities of the solutions of the 

 two types of gelatin differ little or not at all. This indicates that the 

 gelatin salts with univalent metal have at the point of maximal osmotic 

 pressure about three times as many particles in solution as the same 

 mass of gelatin salts with bivalent metal, while the number of electri- 

 cal charges is about the same in both cases. The identity of the con- 

 ductivities of gelatin salts of the type of sodium gelatinate and calcium 



^ Pauli, W., Forlschr. nalunviss. Forschung, 1912, iv, 245. 



^ Michaelis, L., Die Wasserstoffionenkonzentration, Berlin, 1914. 



