JACQUES LOEB 



587 



stead of with gelatin solution, and make the same experiments as 

 described for gelatin, we should expect to find the hydrogen ion con- 

 centration at which the collodion membrane treated with casein is 

 rendered positive to be identical with that found for membranes treated 



Collodion membrane treated with casein 



I 



c 

 o 



• 1 — I 



1 



"S 



480 



440 



400 



360 



320 



280 



240 



200 



160 



120 



80 



40 







point 4.7 



Fig. 3. Collodion membranes treated with casein. Reversal of sign of charge of 

 membrane at pH below 4.7, on the add side of the isoelectric point of casein. 



with gelatin. Fig. 3 shows that this is correct. The curves for 

 membranes treated with casein show a steep rise at a pH of 4.0 or 

 slightly above, but below 4.7. The same is true for membranes 

 treated with egg albumin (Fig. 4). The curves show a steep rise 



