CORRECTNESS OF THE CHEMICAL VIEWPOINT 41 



always to 100 c.c., it is found that the resulting hydrogen ion 

 concentration of the solution is different from the pH which is 

 found when the same amount of acid is added to the same quan- 

 tity of pure water. This is due to the fact that part of the acid 

 combines with the protein as originally suggested by Bugarszky 

 and Liebermann. 1 On the basis of Werner's 2 idea the HC1 should 

 combine with the NH 2 groups of the protein molecule in the same 

 way as if it were added to NH 3 , thus forming a salt of the type 

 RNH 3 C1. This is intelligible on the basis of the recent theories 

 of G. N. Lewis, 3 Kossel, 4 and Langmuir. 5 Gelatin chloride may 

 therefore be expected to dissociate electrolytically in the following 

 way: 



Gelatin NH 3 O1 ^ gelatin NH 3 + Cl 



Hence, the concentration of the free Cl ions in a watery solution 

 of HC1 should remain the same if a small amount of isoelectric 

 gelatin is added, provided the electrolytic dissociation is complete. 

 This was tested by comparing the pCl of HC1 solutions with and 

 without gelatin (Table I). Both the pH and the pCl were 

 measured electrometrically. Table I shows that this pCl was 

 in solutions of HC1 without gelatin always identical with the 

 pH of the same solution. In a second set of experiments the 

 same HC1 solutions contained each 1 gm. of isoelectric gelatin in 

 100 c.c., and the pH and pCl in these 1 per cent solutions of 

 gelatin chloride were also determined after the reaction was com- 

 plete. The reader will notice from Table I that the values for 

 pCl of the watery solutions are within the limits of accuracy of 

 the determinations identical with those found in the gelatin 

 solutions containing the same amount of acid. The pH, however, 

 is different in the aqueous and in the 1 per cent gelatin solutions, 



1 BUGARSZKY, S. and LIEBERMANN, L., Arch. ges. Physiol., vol. 72, p. 

 51, 1898. 



2 WERNER, A., " Neuere Anschauungen auf dem Gebiete der anorganischen 

 Chemie," 3rd ed., Braunschweig, 1913. 



3 LEWIS, G. N., J. Am. Chem. Soc., vol. 38, p. 762, 1916. 



4 KOSSEL, W., Ann. Physik, vol. 49, p. 229, 1916. 



5 LANGMUIR, I., J. Am. Chem. Soc., vol. 41, p. 868, 1919; vol. 42, p. 274, 

 1920. 



