86 



Dr. A. C. Eankin. 



[June 12,. 



(vii) It is thus evident («) that oxygen must be present in order that these 

 three metals, zinc, aluminium, and copper, may manifest bactericidal, 

 properties (in Montreal tap water), and (b) that in the process of interaction 

 between the oxygen and tlie first two of these metals hydrogen peroxide 

 becomes developed, whereas it is not detected in the case of the third. 



Are we justified in drawing any conclusions as to the essential nature 

 of the process of bacterial destruction that occurs in the presence of these — 

 and possibly of other — metals ? I am inclined to think that our general 

 conception of the mode of production, and, it may be added, of the mode- 

 of disinfectant and sterilising action of hydrogen peroxide supplies the 

 clue. We may lay down that the molecule of oxygen coming into contact, 

 with any of these three metals becomes dissociated with the liberation of 

 free ions, of which, in the case of zinc and aluminium, some combine with 

 the molecule of water to form the peroxide, and that it is these free ions,, 

 or in more old-fashioned language, " nascent oxygen," that is the essential 

 agent in the bactericidal process. It is in this way that we explain the 

 bactericidal activity of peroxide of hydrogen (for although I have laid downi 

 that in these particular experiments the amount of hydrogen peroxide- 

 developed was inadequate to explain tlie marked destruction of the bacteria, 

 it must be remembered that this compound has notable disinfectant powers). 

 We believe that the molecule of the peroxide coming into contact with 

 the bacteria becomes dissociated, and that the liberated ion of oxygen is- 

 the destructive agent. It is quite possible that the hydrogen peroxide- 

 formed is thus a subsidiary agent in the bactericidal process where zinc 

 and alunnninm are present. It seems, however, simpler to presume that, 

 the dissociation of the oxygen molecule in the presence of water is the 

 feature common to all three metals, and that in the case of the zinc and 

 aluminium experiments the free ions of oxygen act upon the bacteria 2)i'ior 

 to, or, more accurately, in preference to, becoming associated with the 

 molecules of water to form the peroxide, a certain excess, however, under- 

 going tlie latter combination. With regard to copper it must be i)ostulated 

 that the greater affinity of the free ions to the copper molecules than to. 

 those of water leads to non-forn)ation of the peroxide or to rapid dis- 

 sociation of such molecules as may become formed. 



Why copper and zinc; have diverse actions in the matter of the production) 

 of liydrogen peroxide 1 do not as a bacteriologist pretend to explain ; I caa 

 but call attention to tl>e facts. 



To Prof. Adami my sincere thanks are due for suggestions and advice^, 

 as also to Dr. Oskar Klotz for his generous assistance, and to Dr. A. A. Uruere 

 for aid given in tlie chemical analysis. 



