November 7, 1919] 



SCIENCE 



441 



solutions standardized according to the method 

 just described. Correct and constant results 

 can only be obtained if such a method of 

 standardization is used. 



Another error which permeates the lit- 

 erature of colloid chemistry is due to Hof- 

 meister's experiments on the influence of 

 different ions on the swelling of gelatin. 

 Hofmeister's experiments Were all made in 

 the presence of an excess of electrolyte, in 

 which the specific effect of different ions can 

 no longer be recognized. When we prepare 

 sodium and calcium gelatinates or gelatin 

 chloride and gelatin sulfate according to the 

 writer's method and put them into distilled 

 water we find that the sodium gelatinate 

 swells considerably more than the calcium 

 gelatinate and that the gelatin chloride swells 

 considerably more than the gelatin sulfate of 

 the same concentration of isoelectric gelatin 

 and of hydrogen ions. If, however, we add 

 neutral salt or alkali to the two solutions of 

 metal gelatinates or neutral salts or acid to 

 the solutions of gelatin chloride and gelatin 

 sulfate the differences in swelling disappear 

 since in all cases the swelling is repressed. 

 It is only necessary to add enough electrolyte 

 so as to make the solution M/4 or even less 

 to completely mask the differences. The 

 writer feels therefore justified in stating that 

 if we wish to compare the effect of different 

 ions on the physical properties of gelatin we 

 must avoid the error of adding an excess of 

 electrolyte to the solution. 



A writer" in Nature has raised the ob- 

 jection that Sorensen's experiments on the 

 osmotic pressure of egg albumin were done 

 in the presence of ammonium sulfate, but he 

 overlooks the fact that Sorensen's experi- 

 ments' were not concerned with the com- 

 parison of the effect of different ions on the 

 osmotic properties of egg albumin. If it had 

 been Sorensen's intention to compare the 

 osmotic pressure of albumin chloride with 

 that of albumin sulfate or of sodium albumi- 

 nate with that of calcium albuminate he 



eNature, 1919, CIV. (September 4), 15. 

 ' Sbrensen, S. P. L., Compt. rend. trav. Lab. 

 Carlsierg, 1917, XII. 



would have found it necessary to take 

 cognizance of the fact that the specific effects 

 of different ions on the physical properties of 

 gelatin (or possibly of proteins in general) 

 are repressed in the presence of an excess of 

 electrolyte. As far as the writer is aware 

 there is no disagreement between his results 

 and views and those of Sorensen, though 

 there is a difference in the method employed 

 and the nature of the protein used. 



The writer's recent experiments seem to 

 indicate that the specific influence of the 

 nature of ions as well as the depressing effect 

 of an excess of electrolyte on the physical 

 properties of colloids are connected with the 

 electrification of water, and that this con- 

 nection seems to be the same in the case of 

 crystalloidal and of colloidal solutions of 

 electrolytes. Since it would exceed the limits 

 of this note to discuss these observations, the 

 reader interested in this feature of the 

 problem is referred to the writer's publica- 

 tions on the subject in the current number^ 

 of the Journal of General Physiology and the 

 Proceedings of the National Academy of 

 Sciences.^ Jacques Loeb 



The Rocketellek Institute 

 POR Medical Eeseakch, 

 New York 



THE AMERICAN CHEMICAL SOCIETY. 

 II 



division op pharmaceutical chemistry 

 I F. O. Taylor, Chairman 



George D. Beal, Secretary 



A new field of phytochemical research opened up 

 by the cultivation of medicinal plants on a semi- 

 economical scale: Edw. Kremers. 



Some of the characteristic toxic principles of 

 western poisonous plants: O. A. Beath. 



A comparison of several methods for estimating 

 quinine and strychnine when occurring in the same 

 solution: A. E. Bliss, Jr. 



Quantitative determination of mercury: Sia- 

 MUND Waldbott. Precipitate the mercury from di- 

 lute solution completely on copper foil, dry and 

 weigh the latter, then expel the mercury by hold- 

 ing the foil above a flame until the gray film has 



8 Loeb, J., J. Gen. Physiol., 1918-19, L, 717; 

 1919-20, II., 87. 



