The Becquerel effect in the presence of dyestuffs and the action of light on dyes

Abstract

When a dye is adsorbed on an electrode and is illuminated, a photo-current flows. The direction of the photo-current shows that the dye may be either oxidized or reduced, and a quantitative investigation has enabled the mechanism of the two reactions to be elucidated. The primary step in the reduction is the direct transfer of an electron from the electrode to an excited dye molecule, and the primary step in the oxidation is the reduction of water to hydrogen atoms by excited dye molecules. The different effects which have been found in photogalvanic experiments with dyestuffs, in solution or adsorbed on the electrode, can be interpreted on this basis, and the significance of these reactions in the bleaching of dyes and tendering of textiles by light is discussed.