pH Effects on the pulse radiolysis of deoxygenated aqueous solutions of sulphur dioxide

Abstract

Dilute deoxygenated aqueous solutions of sulphur dioxide and its related anions HSO^–₃ and SO^2–₃ in the pH-range 2–11 were pulse irradiated and the time dependence of the transient optical absorptions and electrical conductance recorded. Hydrogen atoms and OH radicals abstract hydrogen from HSO^–₃. Also OH radicals react with SO₂ and SO^2–₃ to form the radical ion SO^–₃˙ with an absorption maximum at 255 nm. The SO^–₃˙ radical ions recombine to form sulphate (SO^2–₄) and dithionate (S₂O^2–₆), the reaction rate and relative proportions of products being pH-dependent. In acid solutions the SO^–₂˙ radical ion with an absorption maximum at 360 nm is also formed, presumably by reaction of hydrogen atoms with sulphur dioxide. The SO^–₂˙ radical ions recombine to form dithionite (S₂O^2–₄).