256 



ION SI;RIES and proteins. II 



the supernatant solution was drained off from the gelatin, the latter 

 melted, and the volume brought to 100 cc. by adding distilled water 

 of pH of about 5.6, and the pH of the gelatin solution was determined 

 (third row, Table III). 



It is obvious that the pH of the supernatant solution is higher than 

 that of the gelatin solution, as we should expect from the Donnan 

 equilibrium. 



q 



3 55 



pH 4 



8 



10 



11 



12 



Fig. 3. Curves for the effect of different bases on swelling. Those for LiOH, 

 NaOH, KOH, and NH4OH are practically identical and about twice as high as 

 those for Ca(0H)2 and Ba(0H)2. 



Fig. 3 gives the curves for the action of alkalies on swelling. The 

 curves for Li, Na, K, and NH4 gelatinate of the same pH are practi- 

 cally identical, except that the values for NH4OH are irregular for 

 pH above 8.5 possibly on account of the fact that the concentration 

 of NH4OH required to bring gelatin to such pH is rather high. The 

 main fact is that the ratio of the maximal swelling of gelatin salts with 

 bivalent cation like Ca or Ba is half or possibly a little less than half 

 of that of gelatin salts with monovalent cation, like Na, K, or NH4. 



