84 



Dr. A. C. Eankin. 



[June 12, 



peroxide reaction was stronger than with aluminium, and the metal exhibited 

 a more pronounced germicidal action. 



With 50 grammes of zinc the plate was usually free from colonies, 

 although occasionally a few colonies would develop. It was noticeable again 

 that if the surface of the metal was not clean the yield of peroxide was 

 slight and the reduction of the organisms in the water not so marked. 



Germicidal Effects of Copper. — Pure sheet copper was then suljstituted for 

 zinc. The following experiment sets forth the germicidal action of copper in 

 this method of experimentation. It will be seen that copper exhibits quite a 

 marked bactericidal effect, and that without the production of peroxide of 

 hydrogen. Small quantities of copper could be detected in the water in about 

 0-0015 part per 100.000. 



Metal. 



Water. 



Time. 



Plate before, 

 1/20 c.c. 



Plate after, 

 1/20 c.c. 



Peroxide of 

 hydrogen. 







CO. 



lioirr. 









Copper. 





150 



1 



Innumerable 



None 



None. 





125 



150 



1 



" Jl 





)i 





125 



150 



1 





)» 



)> 





100 



150 



1 







)» 





.... 75 „ 



150 



1 



ii 





:j 





50 



150 



1 











50 



150 



1 





33 







25 



150 



1 



If 



Numerous 







10 



150 



1 





)» 



>> 



By reference to this table, it will be seen that 50 grammes of copper is not 

 as strong a germicide as a similar quantity of zinc. Nevertheless, under the 

 conditions of the experiment, it exhibits a strong germicidal action. This, as 

 already noted, is: (1) in the absence of production of peroxide of hydrogen, 

 and (2) under the conditions in which the amount of cop])er passing into 

 solution is inadequate to explain the effects. We further have determined 

 (3) that copper in tap water, with a free supply of oxygen, exhibits a stronger 

 germicidal action than does ordinary taj) or boiled water, and also (4) that 

 when water is treated in the same manner, and for the same length of time, 

 without copper being present, and is inoculated with J>. eoli in similar 

 proportions, there is little, if any, reduction of the number of B. coli in the 

 water. 



Littl(! attempt has l)Ocn made in the past to associate tlie bactericidal 

 influence of metals with oxidation or other effects produced by those nx^tals. 

 We learn that Novy and llcmlry have carriccl out ccitaiii studies upon tin; 

 production of " organic peroxides" by metals, and the (ifl'ect of tlio same upon 

 bacteria, l)ut altliough sotne of their results were communicated verbally 



