806 GELATIN AND CONDUCTIVITY 



DISCUSSION. 



The results charted in Fig. 2 may be explained as follows. The 

 addition of gelatin to a solution of sodium chloride has two possible 

 effects, which tend to oppose each other, (1) to increase the con- 

 ductivity by the addition of ionized gelatin salts and (2) to decrease 

 the conductivity by the mechanical interference of the large undis- 

 sociated gelatin molecules. It could be predicted from the newer 

 conceptions of the physical chemistry of the proteins that the first 

 of these effects would be considerably greater at pH 3.3 than at 

 pH 5.1, which is near the isoelectric point of gelatin and futhermore, 

 it would be expected that the results obtained at pH 7.4 would be 

 more nearly like the results observed at pH 5.1 than like those ob- 

 served at pH 3.3. Whether the addition of gelatin at a given hydro- 

 gen ion concentration increases the conductivity or depresses it 

 depends, therefore, upon the degree of ionization of the gelatin at 

 that reaction. It is obvious that at the reaction of blood, the pure 

 protein, gelatin, is so little ionized that the mechanical interference 

 predominates and the conductivity decreases with each increment of 

 gelatin. 



CONCLUSIONS. 



1 . In pure gelatin solutions the conductivity of the solution increases 

 with increasing concentrations, regardless of the hydrogen ion con- 

 centration. The actual value of the specific conductivity is greater 

 at that reaction where the degree of ionization is greater. 



2. The addition of gelatin in increasing concentrations to a 0.6 

 per cent sodium chloride solution affects the conductivity of that 

 solution in two ways: (a) At pH 3.3, (where gelatin is highly ionized) 

 the conductivity increases with each added increment of gelatin. 

 (b) At pH 5.1 and 7.4 (where gelatin is less highly ionized) the con- 

 ductivity decreases with each added increment of gelatin. 



A similar study is being made of crystalline egg albumin. 



