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Atmospheric Chemistry Laboratory, Department of Chemistry, University of Rajasthan, Jaipur-302 004, India Police Forensic Science Laboratory, Jaipur, India Maharshi Arvind Institute of Engineering & Technology, Jaipur, India Government College, Jhalawar, India Government College, Dausa, India L. B. S. College, Jaipur, India Manuscript received 22 September 2004 Kinetics of the osmium(VIII)-catalysed oxidation or sulfur(IV) by dioxygen in stirred solutions obeys the rate law (A) in phosphate buffered alkaline medium, and the rate law (B) in acetate buffered acidic medium. Robs = k[OsVIII][SIV][OH-]-1 (A) Robs = k3[OsVIII][SIV]2[H+]-1 (B) The kinetics order in [O2) is zero. The rate is comparatively faster in alkaline medium. The proposed mechanisms involve the OsVIII/OsVI cycle perpetuated by reduction of OsVIII by SIV, and regeneration of OsVIII by oxidation of osmium(Vl) by O2 as cooxidant. There is spectrophotometric evidence for the formation of an intermediate complex in acid medium. |
