134 



THEORY OF COLLOIDAL BEHAVIOR 



gelatin phosphate of pH 3.98 the 

 calculated P.D. was 34.0 and from 

 Table XIII we notice that for gela- 

 tin sulphate of pH 3.98 the calcu- 

 lated P.D. was 22.2 millivolts. This 

 is (within the limits of accuracy 

 of the observations) the ratio 3:2, 

 which the theory demands. For 

 pH 4.31 the P.D. is 31 in the case 

 of gelatin chloride and phosphate 

 and for pH 4.34 it was 20.5 for 

 gelatin sulphate, again the ratio of 

 3:2. The strict confirmation of 

 the valency ratio came out clearly 

 in the following experiment which 

 was undertaken for another pur- 

 pose on account of its analogy 

 with antagonistic salt action but 

 which shows that for the same pH 

 the values of the calculated P.D. 

 for gelatin chloride and sulphate 

 are in the ratio of 3:2. 



Solutions of 1 gm. of isoelectric 

 gelatin were prepared in 100 c.c. of 

 water containing 5 c.c. of a mixture 

 of 0.1 N HC1 and 0.1 N H 2 SO 4 in 

 various proportions. The solu- 

 tions were put into collodion bags 

 of about 50 c.c. volume and the lat- 

 ter were put into 350 c.c. of H 2 O 

 containing mixtures of N/1,000 HC1 

 and N/1,000 H 2 SO 4 in the same 

 proportions as inside. The arrange- 

 ment was that described for os- 

 motic pressure measurements, and 

 the osmotic pressure, P.D., and pH 

 inside minus pH outside, were 

 measured after 24 hours at 24C. 

 The upper rows of Table XV give 



