Prolonged Irradiation of Dilute Aqueous Solutions of Redox Couples

Abstract

On prolonged irradiation, the potential of an inert electrode immersed in aqueous solutions of a wide range of redox couples assumes a steady value (equivalent redox potential, ERP) which is determined in some cases by hydrogen peroxide and in others by the redox couple. Irradiation of arbitrary concentrations of these redox couples leads to net oxidation or reduction according to whether the ERP is greater or less than the equilibrium potential of the couple. A theory is proposed which defines the conditions under which the ERP is established and predicts that when it is redox controlled, ERP = E(H2O2)-A where A is 24 mV for 6Co y-radiation and — 1.8 mV for 21oPo a-particles (0<pH<2). The theory predicts that the ERP is independent of the nature of the redox couple and of the intensity of the radiation ; it also explains why the ERP is not established on prolonged irradiation of redox dyes.