202 LAURENCE F. FOSTER 



Paul and Kronig (1896, 1897) in 1896 pointed out that the 

 toxicity of metalUc salts for anthrax spores and for cells of 

 Staphylococcus aureus is dependent chiefly upon the effect of 

 the cation but that the anions and undissociated molecules as 

 well may exert a certain influence. Strong acids were found to 

 act in accordance with their concentration of hydrogen ions 

 and to depend to a small extent upon the specific action of 

 the particular anion or undissociated molecules. Winslow and 

 Lockridge (1906) in an extensive study of the toxic effects of 

 certain acids upon colon and typhoid bacilli found that strong 

 acids such as HCl and H2SO4 proved fatal in concentrations at 

 which they were highly ionized, whereas weak acids such as 

 acetic and benzoic, proved fatal at concentrations where they 

 were but sUghtly ionized. In the latter the effect appeared to 

 be due rather to the whole molecules than to the actual concen- 

 tration of hydrogen-ions. 



Paul, Birstein, and Reuss (1910a) attributed a considerable 

 toxic influence to the acid anion present as well as to the undis- 

 sociated molecules. The toxic action of hydrogen-ions upon the 

 cell appeared to be catalyzed by anions. This was found to be 

 especially true of the weak organic acids. This finding has been 

 supported by Norton and Hsu (1916) who added that the undis- 

 sociated molecules act as negative catalyzers of the action of the 

 hydrogen-ions. Addition of a salt having the same anion as the 

 acid in question was found to decrease the disinfecting power 

 through depression of the hydrogen-ion concentration (common 

 ion effect), though the retarding influence appeared to be greater 

 than would be expected from the decreased hydrogen-ion con- 

 centration alone. Salts not appreciably affecting the ionization 

 of the acid brought about an increase in disinfecting power. 

 These conclusions are not in accord with other results reported 

 by Paul, Birstein, and Reuss (1910b) These observers showed 

 that salts which exercised no disinfecting power in themselves 

 were capable of increasing the toxicity of inorganic acids having 

 the same or different anions. 



A direct relationship between the degree of ionization of acids 

 and their toxicity for yeast cells was reported by Bial (1902) 



