Oxidation studies. VII. Oxidation of hydrazine sulphate and hydroxylamine by cobalt (III)

Abstract

Kinetics of oxidation of hydrazine sulphate and hydroxylamine by Co³⁺ in nitric and sulphuric acid media at 10-15°C. were studied. In H₂SO₄ medium, kinetic evidence was obtained for complex formation between Co³⁺-Substrate for both substrates whereas no such evidence was found in HNO₃ medium. The effects of [H⁺], μ [HSO₄⁻], [SO₄⁻], [Co²⁺] and temperature on the reaction rates were studied. An inverse dependence of the rates on [H⁺] was noticed in both media with both substrates but decreasing effect of [HSO₄⁻] was observed only with NH₂OH in H₂SO₄ medium. Conclusions were drawn as to the nature of the active species: In H₂SO₄ medium for hydrazine sulphate, Co³⁺ (aq.) was concluded to be the active species; similarly for NH₂OH, CoOH²⁺ was the active species. In HNO₃ medium for both substrates CoOH²⁺ was the active oxidant. Nitrogen and Ammonia were found to be the products of oxidation with both substrates in both media. Stoichiometries were established and suitable mechanisms were proposed. The rate laws were formulated and the various equilibria and rate constants were evaluated.