Radiation Chemistry of Ferrous–Ferric Systems

Abstract

THE action of ionizing radiation upon dilute solutions of ferrous sulphate in sulphuric acid has been studied for many years¹, chiefly because of the usefulness of this system for measuring the absorbed energy of the radiation. There has, however, been no consistent theory developed to explain the mechanism of the reaction. Under the conditions normally employed in radiation dosimetry, namely, 10⁻³–10⁻⁴ M FeSO₄ in 0.8 N H₂SO₄, 100 per cent oxidation of the ferrous ion is observed, while ferric solutions are not reduced at this acidity. At lower acidities more complicated results are obtained², and the dependence on pH has never been satisfactorily explained. The experiments of Spicer³ on ferric chloride solutions show that it is possible to reduce ferric solutions under suitable conditions. Indeed, on the basis of the mechanism proposed by Weiss⁴ to explain radiation effects in aqueous solutions, in which the primary chemical act is the formation of hydrogen atoms and hydroxyl radicals, the reduction of ferric ion seems quite likely.