Section III., 1908. [ 171 ] Trans. R. S. C. 



XV. — Production of Hydrogen Peroxide by contact of Metals with Water 

 containing dissolved Oxygen. 



Bj G. W. Sheaeer, M.Sc. 



Demonstrator of Physics, McGill University. 



(Communicated by Professor H. T. Barnes, D.Sc.) 

 (Read May 28th, 1908.) 



When two aluminum electrodes are placed in air or oxygen-free 

 water they show no potential difference, but if one is placed in air-free 

 and the other in air-charged water, a large potential difference of 

 0,7-0.8 volts is developed. The electrode in air-free water is electro- 

 positive to that in the air-charged water.^ Other metals were tried, and 

 some gave similar, but smaller results, while still others showed no 

 effect, notably magnesium. 



Thus, if we make up a cell with aluminum and magnesium elec- 

 trodes in air-charged water, we obtain a potential difference of almost a 

 volt as the result of the following cycle: 



where Al (0) and Mg (0) stand for aluminum and magnesium in air 

 or oxygen-charged water. 



Cells of the above type have been studied by several investigators, 

 and show some very interesting characteristics. For instance, in a cell 

 made up of Mg-Al., (So^)3-Al, the e.m.f. is about 1.3 volts. This is 

 raised to 1.7 on addition of hydrogen peroxide and rises to about 3 volts 

 when short circuited. This rise is gradual, and after reaching a maxi- 

 mum there is a slow fall; addition, of fresh peroxide always sending it 

 back to its high value. 



It has been found that this peculiar action is associated with the 

 presence of the H^Oo about the aluminum electrode, and with the sur- 

 face film, which is present upon all aluminum surfaces exposed to air or 

 to electrolytic oxidization. But the abnormally high e.m.f. developed 

 between two metals (Al and Mg), which are so close together in the 

 electro-chemical series, was not so easy to explain. Prof. Bancroft sug- 



^Am. Electrochem Sec., Vol. 3., p. 95 (1903). Ibid. Vol. 12, p. 54 (1907). 



