JACQUES LOEB 



501 



ing were ascertained. The results are plotted in Fig. 13. Gelatin 

 treated with Ce2Cl6 solution from m/4 to m/2048 becomes insoluble 

 and the cerium gelatinate forms a precipitate. The values for con- 

 ductivity, etc., were as low as those obtained for gelatin at the 

 isoelectric point. The gelatin treated with m/4096 or less concen- 

 trated Ce2Cl6 was clear and gave values for conductivity, etc., rising 



heavy Precipitcite Clear 



Cef Ig M M M tlJ^_t^_M__M_M_M__M__M_ _M_ 

 cone. 4 8 16 32 64 128 256 512 1024 20484096819216384 

 pH 54 58 6.1 62 6.3 6.4 6.4 64 64 64 67 6.8 6.9 70 



Fig. 13. Impure gelatin (chiefly calcium gelatinate) of pH7.0 treated with con- 

 centrations of Ce2Cl6 varying from m/4 to m/16,384, then freed from excess of 

 salts. pH of the gelatin solution is given under each solution. Cerium gelatinate is 

 insoluble and hence the values for swelling, alcohol number, osmotic pressure, and 

 conductivity are almost zero except when the concentration of the Ce2Cl6 used was 

 low (m/4096 and less), when only a fraction of the original calcium gelatinate was 

 transformed into cerium gelatinate. 



with increasing solutions of Ce2Cl6. In these cases not all the Ca 

 gelatinate was transformed into Ce gelatinate. The less Ce gelati- 

 nate was formed the higher the value for conductivity, osmotic pres- 

 sure, alcohol number, and swelling. The pH was between 5.4 and 7.0 ; 

 i.e., on the alkaline side of the isoelectric point of gelatin. Lead and 

 copper acetates gave a similar result, as was to be expected. 



