TOXICITY OF ACIDS TO CILIATE INFUSORIA 



459 



TABLE 3 

 Toxicity of solutions of equal Ph at 20°C. Time in minutes 



confirms the idea suggested above that the H ion is not the only- 

 toxic agent in acids. It is interesting to compare the order of 

 efficiency found with equinormal and equal Ph solutions. The 

 general conditions can be made out from curves 1 and 3 ; stated in 

 tabular form, they are as set forth on page 460. 



The general order for Paramoecium in equinormal solution is 

 hydrochloric > salicylic > formic > dibasic and hydroxy acids 

 > acetic and butyric; but in solutions of equal Ph acetic and 

 butyric become equal in toxicity to the cyclic acids, and the 

 dibasic and hydroxy acids together with hydrochloric become 

 least toxic of all. Formic, which in equinormal solution is 

 more toxic than the other fatty acids, probably because of its 

 greater dissociation, becomes less toxic than the rest when the 

 solutions have the same Ph. Somewhat the same conditions 

 hold with Euplotes. In solutions of equal Ph salicylic retains 



