470 M. E. COLLETT 



CONCLUSIONS 



1. The order of toxicity of a series of acids varies with the 

 concentration, the temperature, and the species. The action is 

 therefore not simple. 



2. The H ion is an important factor, for the toxic order of 

 equinormal solutions is roughly parallel with the order of 

 dissociation. 



3. The H ion is not the only factor in toxicity, for in solutions 

 of equal Ph the acids are not equal in toxicity. 



4. Depression of ionization shows that the anions of certain 

 acids are toxic to both Paramoecium and Euplotes, viz., formic, 

 acetic, propionic, butyric, valeric, citric, benzoic, phthalic, 

 salicylic. The anions of oxalic, tartaric, lactic, and malonic are 

 toxic to Paramoecium, but not to Euplotes. 



5. The temperature coefficients indicate that both chemical 

 and physical reactions are probably concerned in the toxic effect 

 of acids. 



6. A most marked irregularity is shown by acetic and butyric 

 acids, in that their toxicity to Euplotes (though not -to Para- 

 moecium) is greatly increased by temperatures below as well as 

 above 20°C. 



