THE RADIOLYSIS OF HCl–HBr MIXTURES

Abstract

Bromine was the only halogen formed in irradiated mixtures of HCl and HBr. A study of its effect on the hydrogen yield from HCl showed that it reacted with the first hydrogen-forming species (or its precursor), and indicated the same yield for this species as did the earlier experiments with chlorine. The results were consistent with thermal hydrogen atoms, formed in the reaction[Formula: see text]as the first hydrogen-forming species, and hot hydrogen atoms, resulting from the dissociation of excited HCl molecules, as the second species.The hydrogen yield from liquid HBr at −79°C was a factor of two larger than that from liquid HCl at the same temperature, and in mixtures of the two the hydrogen yield increased gradually from a value characteristic of pure HCl [Formula: see text] to one characteristic of pure HBr [Formula: see text] The smaller yield from HCl cannot be explained by radical combinations:[Formula: see text] [Formula: see text]in the radiation tracks and must be attributed either to differences in the ion-combination reactions in the two liquids or to a genuinely greater yield of ions and/or dissociative excited molecules in HBr. The hydrogen yield from solid HBr at −196 °C was [Formula: see text].