70 M. E. COLLETT 



the organic acid alone. This might be interpreted as evidence of 

 the toxicity of the organic anion, which would be removed as ioni- 

 zation of the organic acid was depressed by the addition of HCl. 

 An equally plausible interpretation would be that the organic 

 molecule itself (present in considerable amount before the addi- 

 tion of HCl) is toxic, and that it is antagonized up to a certain 

 point by the increasing acidity of the mixture. Without further 

 evidence it is difficult to decide which interpretation is most 

 nearly coi*rect. Some preliminary experiments with xylol indi- 

 cate that the addition of a small quantity of HCl has a dis- 

 tinctly antitoxic influence. A slight increase in pH may thus 

 under certain conditions have a protective effect. In this 

 respect the H ion acts similarly to other cations in certain forms 

 of salt antagonism (Lillie, '12, '13 Osterhout, '18). 



Xylol 0.6 saturated solution in water 



A second means of approach is at hand in a study of the relative 

 toxicity of the organic acids alone and when combined with their 

 sodium salts. 



The toxicity of the different sodium salts of the organic acids 

 when used alone varies somewhat at different concentrations, 

 as is indicated in the following series (table 2). 



0.1 M 



Paramecium: Benzoate = citrate = salicylate > tartrate > 

 succinate > formate — valerianate > chloride > lactate. 



Euplotes: Benzoate = citrate > salicylate = tartrate = 

 chloride > butyrate > valerianate > formate = lactate > 

 succinate > acetate. 



0.01 M 



Paramecium: Salicylate = benzoate = tartrate = succinate > 

 citrate > formate-valerianate = chloride = lactate. 



