804 



GELATIN AND CONDUCTIVITY 



cent is from 0.3 to 1.5 at pH 5.1 while at 3.3 the range is from 6.6 

 to 30.9. This difference in ionization with change in hydrogen ion 

 concentration has been thoroughly studied in 1 per cent gelatin solu- 

 tions by Loeb.^ 



The next series of experiments, Table II, bears more directly upon 

 the original problem and consists of observations on the effect of 

 gelatin upon the conductivity of a 0.6 per cent sodium chloride 

 solution. The concentrations of gelatin and the reactions of the 

 final solutions were the same as were used in the first experiments. 

 Fig. 2 shows the results plotted on a common scale, conductivities 

 again as ordinates and concentrations of gelatin in per cent as abscissae. 

 The curves for each pH are appropriately labeled. All three curves 



TABLE II. 

 Conductivity of 0.6 per cent NaCl Solutions with Increasing Gelatin. 



are apparently straight lines. At pH 3.3 the conductivity increases 

 consistently with the concentration of gelatin; at pH 5.1, however, 

 the conductivity decreases strikingly with increasing amounts of 

 gelatin. At pH 7.4 the conductivity again decreases with each 

 increment of gelatin but the depression of the conductivity is less 

 marked than at pH 5.1. Clearly the addition of gelatin at pH 3.3 

 to a solution of sodium chloride increases the conductivity of the 

 solution; while the addition of gelatin near the isoelectric point 

 (pH 5.1) decreases the conductivity in proportion to the amount of 

 gelatin added. At the reaction of blood, also, the addition of gelatin 

 to a sodium chloride solution depresses rather than increases the con- 



3 Loeb, J., J. Gen. Physiol., 1920-21, iii, 247. 



