76 



M. E. COLLETT 



EXPERIMENTAL EVIDENCE 



The toxicity of acetic acid is considerably lessened by the 

 addition of appropriate amounts of the chlorides (table 1). 

 Among the chlorides of the alkali metals the antagonism is 

 greatest with NaCl and least with NH4CI (which in itself is 

 very toxic). The higher concentrations are especially effective 

 with Paramecium; with Euplotes they are very toxic, although 



TABLE 1 



ACETIC ACID 0.001 N 



Concentration of salts M 



Monovalent cations 



Bivalent cations 



Alone 



Plus NaCl 



Plus KCl 



Plus NH4CI 



Plus BaCla 



Plus CaCla 



Plus MgCl, 



PlusSrCU 



Plus BaCla plus NaCl. 

 Plus CaCla plus NaCl. 

 Plus MgCl2 plus NaCl 

 Plus SrCl, plus NaCl. 



Plus CdCl2 



Plus CoCl, 



Plus MnCl. 



Plus NiClo 



Plus ZnCls 



0.0 



LENGTH OF LIFE IN MINUTES 



Paramecium 



0.005 

 0.0005 



25 



45 



0.01 

 0.001 



35 



4 

 3 



6 

 50 



6 

 10 



<1 



2 



3 



<1 



<1 



0.05 

 0.005 



12 

 5 

 4 



65 



8 

 25 



15 

 90 

 12 

 35 



<1 

 3 



7 



0.1 

 0.01 



11 

 5 



4 



10 



70 



9 



40 



10 

 50 



7 

 20 



<1 

 3 

 9 



Euplotes 



12 



0.005 

 0.0005 



15 



20 



6 



0.01 

 0.001 



30 



15 



5 



40 

 63 

 20 

 40 



SO 



160 



15 



85 



7 

 4 

 6 

 4 

 4 



0.05 

 0.005 



70 

 90 

 40 

 40 



180+ 



180+ 



180+ 



5 



10 



6 



15 



0.1 

 0.01 



7 

 7 

 4 



80 



120 



30 



50 



180+ 



180+ 



180+ 



5 



10 



7 

 18 



lower concentrations are fairly efficient. This is to be correlated 

 with the fact that Euplotes is much less resistant than Parame- 

 cium to NaCl alone, at least in concentrations of 0.05 M and above 

 although this is not the case at 0.01 M. At the optimal concen- 

 tration the length of life is increased four times for Paramecium 

 and two or three times for Euplotes by the addition of NaCl to 

 the acid. 



