84 



M. E. COLLETT 



The efficiency of the alkahne earth chlorides here as with eaproic 

 is: 



Paramecium: Ca > Sr > Ba > Mg 

 Euplotes: Ca > Sr > Ba > Mg 



When NaCl is added to the mixture of acid and alkahne earth 

 chloride there is at all concentrations a further decrease in toxicity 

 as in the case of eaproic. The heavy metal chlorides are even 

 less efficient, although the same order holds as with eaproic and 

 acetic; here, too, there is an increase in antagonistic power with 

 the addition of NaCl. 



TABLE 6 



SUCCINIC 0.0005 N 



Concentration of salts M. 



Monovalent catioifs 



Bivalent cations 



Alone 



Plus NaCl 



Plus KCl 



PIUSNH4CI 



Plus BaCh 



Plus CaCl. 



Plus MgCl2 



Plus SrCh 



Plus BaCh plus NaCl . 

 Plus CaClaplus NaCl. 

 PlusMgCla plus NaC. 

 Plus SrCl2 plus NaCl . . 



LENGTH OF LIFE IN MINUTES 



Paramecium 



0.0 



0.005 

 0.0005 



0.01 

 0.001 



15 



10 



50 

 10 



18 



14 

 90 

 10 

 30 



0.05 

 0.005 



18 



7 

 4 



12 

 70 

 11 

 30 



30 

 180 



15 

 120 



0.1 

 0.01 



Euplotes 



0.0 



10 

 5 

 3 



15 

 80 

 10 

 45 



18 



120 



15 



25 



0.005 

 0.0095 



0.01 

 0.001 



15 

 15 

 15 



120 



180 



20 



120 



120+ 



120+ 



80 



130+ 



0.05 

 0.005 



15 



18 



4 



180+ 



180+ 



180+ 



10 



0.1 

 0.01 



10 



22 



3 



100 

 180 



35 



40 



120 

 4h 



180+ 

 10 



These results hold for benzoic, salicylic, and phenylacetic, 

 but for succinic (table 6) we must turn to HCl (table 7) or to 

 tartaric and the other hydroxy-acids (tables 11, 12, 13) for a par- 

 allel. The addition of NaCl to a hydroxy-acid may increase or 

 leave unchanged its toxicity to Euplotes at the same time that 

 it protects Paramecium in the usual way, just as was the case 

 with acetic. The efficiency of the alkaline earth chlorides is for 

 both organisms, Ca > Sr > Ba > Mg. This differs slightly from 

 the order with acetic (Paramecium, Ca > Sr > Ba = Mg; 



