242 ELECTROCHEMISTRY 



which are in satisfactory accord with the high diamino-acid 

 content of the salmin molecule (4). 



Summing up these results, therefore, we see that in the forma- 

 tion of the salts of proteins with acids diamino radicals are primarily 

 concerned, while in the formation of the salts of protein with bases 

 dicarboxylic radicals are primarily concerned. The correspondence 

 between the diamino-acid content of a protein and its binding 

 capacity for acids, to which Kossel has drawn attention (loc. cit.), 

 and that between the dicarboxylic acid content and the com- 

 bining capacity for bases to which I have drawn attention in 

 the latter part of the first chapter is therefore seen to be not 

 accidental but an expression of an essential feature of the union 

 between proteins and inorganic acids and bases. 

 i 3. The Dependence of the Electrical Conductivity of Solutions 

 of Protein Salts upon the Proportion of Inorganic Acid or Base 

 which the Salt Contains. — In preceding paragraphs we have 

 discussed the effects of dilution upon the conductivities of solu- 



tions of protein salts; that is, of altering the ratio — r— while 



keeping the composition of the salt; i.e., the proportion of protein 

 to base or acid constant. We have found that these effects 

 admit of interpretation in the light of the well-known laws of 

 electrolytic dissociation and of the view that the dissociation 

 of protein salts is accomplished by the splitting of — COH.N — 

 bonds. We must now take up the consideration of the effects 

 of altering, not only the total concentration of the system, but 

 also the proportion of protein to base or acid. 



If we add protein to dilute solutions of an acid or base there 

 usually results a depression, which we shall designate by X, of 

 the conductivity of the solution. I find that when 1 per cent of 

 casein is added to varying concentrations of KOH this depression 

 is connected with the concentration of the KOH solution (= 6i) 

 to which the protein is added by a very simple relation. This 

 relation is of the form 



X X 10-5 = ahi - 0bx^ - y (vi) 



in which a, j(3 and 7 are constants (14). 



Applying this formula to observations in which 1 per cent of 

 casein was dissolved in varying concentrations of KOH * and the 



* These solutions were the same as those employed in the gas-chain measure- 

 ments cited in the previous chapter (1 per cent casein, second series), and, 



