248 ION SERIES AND PROTEINS. II 



It is often asserted that Hofmeister's ion series for swelling has been 

 confirmed by other authors. Thus Zsigmondy- makes the following 

 statements in support of this impression. 



"Wo. Ostwald who compared the efficiency of different acids found that 

 swelling diminishes in the acids in the following order, 



HCl > HNO3 > acetic acid > sulfuric acid > boric acid. 



Fischer has shown that the acid and alkah swelling of gelatin as well as that of 

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

 nitrates have a less dehydrating action than acetates, sulfates, or citrates. We 

 have here a similar series as in the case of the precipitation of proteins by alkali 

 salts, although the order does not agree entirely." 



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

 ments differently from Zsigmondy, since both authors ignored the 

 hydrogen ion concentration of their solutions. We believe to have 

 shown that it is necessary to base conclusions concerning the relative 

 efficiency of ions on experiments with equal hydrogen ion concentra- 

 tion. By ignoring this postulate Ostwald has only succeeded in prov- 

 ing that acetic and boric are weaker acids than nitric but not that 

 gelatin swells less in acetates or borates than in nitrates; and Fischer 

 has only succeeded in proving 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 acetates and citrates 

 diminish the swelling of gelatin. These authors attributed the 

 effects caused by a variation in the hydrogen ion concentration of 

 their solutions erroneously to an influence of the anion. The Hofmeis- 

 ter 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 gela- 

 tin we must proceed from isoelectric gelatin, bring it to different pH val- 

 ues 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 

 practically the same as when it is in combination with CI or NO3; 

 since in all these cases the anion of the gelatin salts is monovalent. 

 Only in the case of gelatin sulfate is the swelling considerably less, 



^Zsigmondy, R., Kolloidchemie, Leipsic, 2nd edition. 1918, 373. 



