TOXICITY OF ACIDS TO INFUSORIA 



81 



just as is the case with acetic. \Anien these chlorides are com- 

 bined with NaCl, even at the highest concentration used, their 

 protective power for both organisms against caproic or butyric 

 is increased many-fold, while with acetic this was true only for 

 Paramecium. Thus Euplotes lives eight minutes in caproic 



TABLE 4 



CAPROIC 0.001 N 



Concentration of salts M 



Monovalent cations 



Bivalent cations ; . 



Alone 



Plus NaCl 



Plus BaCl, 



Plus CaCl2 



Plus MgCl, 



Plus SrCl. 



Plus BaCl, plus NaCl . 

 Plus CaCli plus NaCl . 

 Plus MgCl. plus NaCl. 

 Plus SrCls plus NaCl. . 



Plus CdCl. 



Plus C0CI2 



Plus MnCl2 



Plus NiCl, 



Plus ZnCl. 



Plus CdC], plus NaCl . . 

 Plus C0CI2 plus NaCl . . 

 Plus MnCla plus NaCl . 

 Plus NiCl. plus NaCl . . 

 Plus ZnCla plus NaCl . . 



LENGTH OF LIFE IN MINUTES 



Paramecium 







0.005 

 0.0005 



<1 



<1 



0.01 

 O.COl 







10 

 4 



5 



7 

 20 



8 

 8 



<1 



3 



3 



<1 



<1 



6 



7 

 7 

 3 

 3 



0.05 

 0.005 



5 



18 

 5 

 5 



8 

 35 

 10 

 18 



<1 



4 

 5 



11 

 20 



0.1 

 0.01 



10 



5 



30 



5 



8 



7 

 25 



9 

 13 



<1 



4 

 6 



Euplotes 







10 



005 

 0.0005 



0.01 

 0.001 



16 



30 

 40 

 14 

 20 



35 

 60 

 15 

 45 



5 

 5 

 5 

 5 

 5 



7 

 7 

 8 

 5 

 10 



0.05 

 0.005 



30 

 40 

 15 

 20 



80 60 

 150 100 



80 

 120 



4 

 4 

 6 



15 



55 



180 



0.1 

 0.01 



40 



30 

 60 

 11 

 25 



60 

 100 



6 



5 



12 



18 

 50 

 90 



acid alone, forty-five minutes in acid plus SrCl2 0.01 M, and 180 

 minutes in acid plus SrCla 0.01 M plus NaCl 0.1 M. As to the 

 heavy metals, the order of efficiency with caproic is for both 

 organisms: Mg > Mn > Co > Cd = Ni = Zn. This agrees 

 exactly with the order observed with acetic. When combined with 

 NaCl the antitoxic efficiency of all these chlorides is greatly in- 



