410 



ION SERIES AND PROTEINS. lU 



What has been demonstrated for the effect of these salts on the vis- 

 cosity of gelatin solutions holds also for their effect on the swelling of 

 gelatin. The same volumetric method for measuring the swelling 

 effect was used which was described in the preceding paper. Fig. 11 

 gives the relative depressing effect of NaCl, NaH2P04, NaCNS, mono- 

 sodium tartrate, monosodium citrate, and Na acetate on the swelling 

 of gelatin chloride of pH 3.3 (the curve for Na2S04 is added for com- 

 parison), and Table II gives the variation of the pH of the gelatin 

 caused by the addition of these salts. Our theory demands that all 

 these salts (except Na2S04) should depress the swelling of gelatin 

 chloride of pH 3.3 to the same amount, and that deviations from this 



rule must find their explanation in variations of pH caused by the 

 addition of salt. Table II shows that the variations in pH are small 

 for NaCl, NaCNS, and NaH2P04 and hence the curves for the depress- 

 ing effect of these three salts upon the swelling of gelatin are almost 

 identical, as the valency rule demands. Monosodium citrate and 

 tartrate have a greater depressing effect on the hydrogen ion concen- 

 tration and Na acetate has a still greater depressing effect than these 

 two salts. This explains the apparent deviation of the curves for 

 these three salts from the valency rule. 



Salts like disodium tartrate, disodium oxalate, and trisodium citrate 

 offer an opportunity for an interesting test for our theory on account 



