THE VALENCY RULE AND THE HOFMEISTER SERIES 77 



diminished by the addition of salt, and that chlorides, bromides, and 

 nitrates have a less dehydrating action than acetates, sulphates, or 

 citrates. We have here a similar series as in the case of the precipita- 

 tion of proteins by alkali salts, although the order does not agree 

 entirely." 



The writer is inclined to interpret Ostwald's and Fischer 's 

 experiments differently from Zsigmondy, since both authors 

 ignored the hydrogen ion concentration of their solutions. Our 

 experiments have shown that it is necessary to base conclusions 

 concerning the relative efficiency of ions on experiments with 

 equal hydrogen ion concentration. By ignoring this postulate 

 Ostwald only proved that acetic and boric are weaker acids than 

 nitric but not that the acetate and borate anions have a greater 

 depressing effect on the swelling of gelatin than NO 3 ; and Fischer 

 only proved that citrates and acetates are buffer salts which 

 when added to a solution of a strong acid diminish its hydrogen 

 ion concentration, but not that the acetate and citrate anions have 

 a greater depressing effect on the swelling of gelatin than Cl or 

 NO 3 . Both authors erroneously ascribed the effects of variation 

 of pH to an effect of the nature of the anion. The Hofmeister 

 series of ion effects on swelling has, in reality, never been 

 confirmed. 



If we wish to study the specific effects of ions on the swelling 

 of gelatin we must proceed from isoelectric gelatin, bringing it 

 to different pH by different acids or alkalies and then compare 

 the swelling at the same pH for these different acids or alkalies. 

 If this is done it is found that when gelatin is in combination 

 with the anion of a weak dibasic or tribasic acid, e.g., tartaric, 

 citric, phosphoric, its degree of swelling is the same as when it is in 

 combination with Cl or NO 3 ; since in all these cases the anion of 

 the gelatin salts is monovalent, and that only in the case of gela- 

 tin sulphate is the swelling considerably less, because H 2 SO4 com- 

 bines with gelatin in equivalent and not in molecular proportions 

 as does the weak dibasic or tribasic acid, e.g., phosphoric. 1 



The following simple and quick volumetric method for measur- 

 ing the swelling was adopted. 



Dry powdered gelatin was sifted and the grains no longer 

 going through sieve 50 but going through sieve 40 or 30 were 

 , J., J. Gen. Physiol, vol. 3, p. 247, 1920-21. 



