SALT EFFECTS IN BACTERIAL GROWTH^ '^fivv y^ 



I. PRELIMINARY PAPER ^^kUi., ' 



GEORGE E. HOLM and JAMES M. SHERMAN 



From the Research Laboratories of the Dairy Division, United States Department 

 of Agriculture, Washington, D. C. 



Received for publication February 28, 1921 



The Hofmeister series shows the effects of ions of neutral 

 salts upon the coagulation of colloids and upon the swelling and 

 other physical properties of proteins. Our knowledge of these 

 ion effects in solution has been greatly extended by Freundlich 

 and his students. They noted that the ions could be arranged 

 in a definite order with respect to their effects upon compressi- 

 bility, surface tension, solubility, viscosity, absorption, ratio of 

 reaction, etc. Freundlich seems to favor the hydration theory 

 of salts as an explanation of this neutral salt action, and since 

 the properties affected are so closely related and bound up with 

 one another, and the ions so consistent in their order of effect, 

 he calls these effects ''lyotropic" effects. The lyotropic expla- 

 nation does not lay claim to being a full explanation of neutral 

 salt action, but it does lay claim to correctness in that it system- 

 atically treats complicated phenomena. 



In most cases the influence of the anion far outweighs that of 

 the cation and the order of anion effects usually reads as follows, 

 F>S04>P04>Cl>N03>Br>I>CNS; while the order of ar- 

 rangement for the cation is usually Ca> Sr>Mg> Cs>Rb> 

 K> Na> Li. The same sequence is obtained in the widely 

 differing changes mentioned above and does not seem to follow 

 any recognizable order with respect to valency, atomic weight, 

 etc. Certain reagents may promote or hinder the salt effects 

 as compared with those in pure solution. In some cases the 



1 Published with the permission of the Secretary of Agriculture. 



511 



JOURNAL OF BACTERIOLOGT, VOL. VI, NO. 6 



