262 



THEORY OF COLLOIDAL' BEHAVIOR 



increasing hydrogen ion concentration (i.e. increasing addition of 

 HC1) the concentration of NaCl required for flocculation should 

 first increase and later after a certain pH diminish. We 

 will show that this is the case. 



to 

 



pH 



1.6 





\ 



450 

 425 

 400 

 375 

 350 

 325 



30 

 275 



250 

 225 



200 



1T5 

 150 



125 



100 



75 



50 



25 







)24 512 256 128 



Concentration of NaCl 



FIG. 77. Difference in the depressing action of NaCl solutions on the osmotic 

 pressure of gelatin chloride solution of different pH. 



Ten cubic centimeters of a 5 per cent stock solution of iso- 

 electric gelatin containing various amounts of HC1 were brought 

 to about 45C. and 40 c.c. of absolute ethyl alcohol were added. 





N, r^ 



