172 ROYAL SOCIETY OF CANADA 



gested' that aluminum in the presence of water containing dissolved 

 oxygen, formed hydrogen peroxide, and thus formed a cell with HjO^ 

 as electrode. He suggested the following reaction : — 



2 AlH-6Ho04-302=Al2 (OR) ,-\-3}î,0^ 



The series of experiments, which form the subject of this paper, 

 were made to test this point. A very simple one was first tried. Some 

 carefully cleaned aluminum sheet was placed in well aerated distilled 

 water. After standing for 48 hours, the starch potassium iodide test 

 for the peroxide was applied, and a comparatively strong reaction for 

 peroxide obtained. A sample of the water, which Jiad not been in con- 

 tact with the aluminimi, showed no trace. The starch and KI test was 

 performed as follows : To the sample to be tested a drop of lead acetate 

 was added, followed by a very little weak (1|2^) Kl, some starch solution, 

 and lastly a drop or two of w«ak 3^ acetic acid. A blue colour denoted 

 the presence of hydrogen peroxide. 



Having obtained this indication that the peroxide was formed, 

 several somewhat more elaborate experiments were made. A long glass 

 tube of about 3 cms. bore was filled with clean Al foil and water, and 

 air drawn up through. The yield of H2O2 was greatly increased by this 

 treatment, and reached a maximum in about two hours, after which the 

 action was stopped by the film which had gathered on the aluminum 

 surface. As an electric current tends to remove this film when the 

 aluminum is the cathode, it was thought that it might increase the yield. 

 Accordingly this was tried, a platinum anode being used and air bubbled 

 through the water. But when the test was applied no peroxide could be 

 detected, showing that what caused the removal of the film also caused 

 decomposition of the peroxide. The experiment was then repeated with 

 the direction of the current reversed, and when tested it was found that 

 the yield had been greatly increased, showing that the film and peroxide 

 were formed together. This would indicate that the film and the 

 hydroxide Al2(0H)e v/ere the same. 



The above reaction may be represented as follows: — 



<^ Al as cathode 



2 Al + OHaO + 30, = AI2 (0H)« -f SH.Oj 

 Al us anode > 



The yield was also increased by mechanical agitation and by cool- 

 ing the water to increase the solubility of the oxygen. Air and oxygen 



iJour. Phys. Chem., Vol. 12, p. 155, (1908). 



