io8 COLLOID CHEMISTRY OF THE PROTEINS 



110 



100 

 90 

 80 

 10 

 60 



protein is least. An increase in alkali content at this point 



leads to increasing quantities of it remaining in the free state. 



The results shown in Tables 55 and 56 give the conductivity 



data for increasing dilution of the casein-saturated casemate with 



water. The original 

 solution was made by 

 shaking with 0-03 N 

 sodium hydroxide. 

 Similar figures are 

 given for such a solution 

 diluted with an equal 

 volume of the alkali, 

 forming a caseinate half 

 saturated with casein. 

 The conductivity 

 curves (Fig. 25) run 

 FIG 2 parallel to each other. 



The A a of the salt 



saturated with protein has the value 79, corresponding to 

 Vcaseinate = 28 ; the A a of the half saturated caseinate has the 

 value 83 84, which leads to a value for mobility of the 

 caseinate ion of 32 -5 . Thus the mobility 

 is 14 per cent, less in the saturated solu- 

 tion than it is in the latter case. 



The application of Ostwald's rule 



i^_ JL 

 sootoo ioo 



gives 



1 1024 



A 32 = 3 x 10 -i, or a tri- 



FIG. 26. 



valent casein ion, in both cases. Hence 

 when one passes from the half saturation 

 to the almost complete saturation of 

 the alkali salt with casein there is no 

 change in valency, and only a moderate 

 decrease in mobility of the ions. 



Of course an increase in valency would cause a great rise in 

 the ionic conductivity (see p. 125). We should expect such an 

 increase in valency from the curves showing the course of 

 combination of alkali and casein, when the continued addition 

 of alkali causes new acid valencies of the casein to become active. 



If to a solution of alkali caseinate saturated with casein 



