Browsing by Author "Matthews, Ralph W."

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    Effect of sulphuric acid on the cobalt-60 γ-ray induced oxidation of ferrous sulphate solutions
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1977, 73 (03), 1977) Matthews, Ralph W.
    The effects of variations in sulphuric acid and oxygen concentrations on the yields of ferric ion from cobalt-60 gamma irradiated solutions of ferrous sulphate have been studied. Various kinetic models, some derived from reaction mechanisms suggested in the literature and some derived from new mechanisms, were used to compare calculated G(Fe3+) values with experimental values from over 600 irradiations of solutions ranging in sulphuric acid concentration from 0.04 mol dm–3 acid/0.1 mol dm–3 sodium sulphate to 1.0 mol dm–3 acid. The reaction stoichiometry over the entire range of acid and solute concentration was well described by an equation which incorporated terms for inhibition of charge pair recombination by the acid and solute. The calculated values of G(H + e–aq) are significantly lower than those usually quoted and show little variation with acid concentration; 3.07 ± 0.05 to 3.18 ± 0.05 for the acid range used. G(charge pair) from the model was found to be 0.7 ± 0.05 and G(total ion pair) 4.7 ± 0.15. The ratio of rate constants kH,Fe2+/kH,O2 was found to be (1.14 ± 0.03)× 10–3 and independent of pH.
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    Kinetic Evidence for Excited Water in the Cobalt-60 y-Radiolysis of Ferrous Sulphate in 0.4 mol dm-3 Sulphuric Acid Solutions
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1974, 70 (07), 1974) Matthews, Ralph W.
    The effect of oxygen and ferrous ion concentrations on G(Fe3+) from ferrous sulphate in 0.4 mol dm–3 sulphuric acid solution irradiated with 60Co γ-rays has been studied. The results cannot be fully explained in terms of the accepted reaction mechanism. The marked increase in G(Fe3+)deaer. with ferrous ion concentration is attributed to a reaction between ferrous ion and excited water in competition with pseudo first-order decay of the excited water. In the presence of oxygen the results are consistent with a competing reaction between excited water and oxygen to give hydrogen sesqui-oxide, H2O3, or singlet oxygen, O2(1Δg). Homogeneous kinetics describe the data with good precision for ferrous ion concentrations ranging from 0.2 to 100 mmol dm–3 and for oxygen concentrations ranging from 0.0 to 1.1 mmol dm–3. The method of least-squares was used to obtain the following parameters from the data: GH= 3.67 ± 0.03, kH,Fe2 +/kH,O2=(12.0 ± 0.5)× 10–4, G(Fe3+)deaer.(at [Fe2+]= 0)= 7.68 ± 0.04, GH2O*= 0.49 ± 0.05, kH2O*/kH2O*,Fe2+=(15.0 ± 4.0)× 10–3, kH2O*,O2/kH2O*,Fe2+= 11.7 ± 3.2., The lifetime of the excited water is estimated to be not less than 10–7 s.