PHOTOCHEMICAL FORMATION OF HYDROGEN PEROXIDE FROM WATER PART I IN PRESENCE OF ZINC OXIDE

The photochemical formation of hydrogen peroxide from water with zinc oxide as a sensitiser has been studied in detail both in sunlight as well as in artificial-ultraviolet and visible light. The yield of hydrogen peroxide increases in presence of some organic compounds which presumably act as stabilisers. Of the nine organic substances employed for this purpose, phenol was found to be the best. An increase in the amount of zinc oxide produces a corresponding increase in the reaction rate which, however, tends to a limit with a constant intensity of light. An increase in the pa has been found to increase the yield of hydrogen peroxide. The formation of hydrogen peroxide also takes place in the total tight from a tungsten filament lamp as well as in the violet region of the visible spectrum isolated by means of filters, although in the latter case the reaction is very slow. This indicates that the photosensitive range of zinc oxide extends up to the violet. The photosensitising activity of zinc oxide, prepared. by different methods, has been studied and it has been found that zinc oxide, prepared from carbonate by ignition, has the greatest activity.