title: Kinetics of the light-driven aqueous autoxidation of sulfur(IV) in the absence and presence of iron(II).
abstract: The photochemical autoxidation of aqueous, acidic sulfur(IV) solutions was studied in the absence and presence of iron(II) by a newly introduced technique using a diode-array spectrophotometer, in which the same light source is used to drive and detect the reaction. Based on detailed kinetic and stoichiometric data sets, a non-chain mechanism is proposed for the autoxidation of sulfur(IV). In this mechanism, excited hydrated sulfur dioxide, *H2O.SO2, first reacts with O2 to form peroxomonosulfate ion, HSO5-, which rapidly oxidizes another H2O.SO2 to give hydrogensulfate ion as a final product. In the presence of iron(II), the formation of iron(III) was detected, which can be interpreted through the simultaneous contribution of two additional pathways: some of the HSO5- formed oxidizes iron(II) instead of sulfur(iv), and *H2O.SO2 also reacts directly with iron(II) to yield iron(III). This mechanism provides a sufficient quantitative interpretation of all experimental observations.
authors.affiliation: University of Debrecen, Department of Inorganic and Analytical Chemistry, Debrecen 10, P.O.B. 21, Hungary H-4010.
authors.forename: Ildikó
authors.initials: I
authors.lastname: Kerezsi
authors.forename: Gábor
authors.initials: G
authors.lastname: Lente
authors.forename: István
authors.initials: I
authors.lastname: Fábián