1909.] The Germicidal Actioji of Metals, etc. 81 



Metal. 



Water. 



■ 



rp- ' 1st plate, 

 Time. 1 , ,an 



1/20 CO. 



2nd plate, 

 1/20 C.C. 



Hydrogen 

 peroxide. 



Aluminium ... 50 grammes 

 Zinc 50 „ 



C.C. 



150 

 150 



150 



hour. 

 1 

 1 



1 



Innumerable* 



91 



• 



Innumerable 

 Slight reduc- 

 tion 

 Innumerable 



No reaction. 



* At least 7000 to 8000 colonies per 0 05 c.c. 



The water used ia these experiments was obtained from the tap and held 

 a fair amount of oxygen in solution. It is seen from tliis experiment that 

 there is a bactericidal action (in the case of zinc) without demonstrable 

 production of peroxide of hydrogen. In studying this it seemed possible 

 that the oxygen in solution in the water played, nevertheless, some part 

 in the destruction of the organisms, presumably by interaction with the 

 metal. • 



Effects of Oxygen-free Water. — To investigate this the following experi- 

 ments were performed. Tap water was again used, but previous to placing 

 it in contact with the metals it was boiled for half an hour and then 

 cooled : — 



Metal. 



Water. 



Time. 



1st plate, 

 1/20 c.c. 



2nd plate, 

 1/20 c.c. 



Hydrogen 

 peroxide. 





c.c. 



hour. 









Aluminium ... 50 grammes 



180 



1 



Innumerable 



Innumerable 



None. 



Zinc 50 „ 



180 



1 





J) 



„ 





180 



I 



)> 



}} 





Here we see that there is practically no reduction with any of the metals. 



Effects of Bubbling of Air on the Solubility of the Metal. — In the next 

 experiment water was added to the three metals and air was drawn through 

 the apparatus for a period of one hour, and subsequently the water was 

 tested quantitatively for metal in solution. 



Metal. 



Water. 



Metal in solution. 





c.c. 

 150 

 150 

 150 



Trace — hydrate thrown down. 

 Less than o'6oi5 part per 100,000. 



It can hardly be possible that this small quantity of metal in solution can 

 be responsible for any germicidal action exhibited in the experiments to 



