SALT ACTION 



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comparative tests have been made with salts of one metal combined with different 

 anions, and of one anion combined with different metals. These tests have been 

 conducted not only on various bacteria, but on protozoa, and on the eggs of certain 

 fish. On the whole the results have been reasonably concordant, as may be seen 

 from Table 9, in which the cations are arranged in order of ascending toxicity. 

 It must be understood that strict comparison of the action of different salts can 

 be undertaken only in media of the same H-ion concentration. 



TABLE 9 (modified from Talk 1923). 

 Cations in Series of Inceeasinq Toxicity. 



From this table it will be seen that on the whole those metals of low atomic 

 weight are less toxic than those of high atomic weight, though there are many 

 exceptions. 



To give some idea of the actual strengths necessary to cause inhibition of 

 growth of Bad. coli, some results of Hotchkiss (1923) are given in Table 10. She 

 divides her salts into two groups, the more toxic ones comprising those of the 

 heavy metals, and the less toxic, comprising those of the alkali metals and of 

 the alkaline earth metals. The salts of Group I give neutral solutions ; those 

 of Group II, owing to hydrolysis, yield solutions with an acid reaction. 



