The oxidation of Br À by Cl 2 À is investigated by pulse radiolysis in aqueous solutions of NaCl and NaBr. Depending on the ratio of the concentration of Br À to Cl À , the main product being observed is either Cl 2 À , ClBr À or Br 2 À . The mixed radical anion ClBr À exhibits a broad absorption band at 350 nm with e 350 ¼ 9300 dm 3 mol À1 cm À1 . The rate constants of the equilibrium Cl 2 À + Br À Ð ClBr À + Cl À are determined to be k f ¼ 4 Â 10 9 and k b ¼ 1.1 Â 10 2 dm 3 mol À1 s À1 .

Publication costs assisted by Hahn-Meitner-lnstitut fur Kernforschung Berlin Deaerated aqueous solutions of NiS04 were irradiated with 60Co y rays or by single pulses of high-energy electrons. The solutions contained aliphatic alcohols, diethyl ether, c-pentane, or formate as scavengers for OH and H radicals. Metallic nickel was precipitated from some of these solutions upon 7 Irradiation. Reactions between Ni+ and organic radicals leading to organic nickel compounds were observed in the pulse experiments using both optical and conductimetric detection methods. The rate constants of reactions of Ni+ with organic radicals are of the order of 109 M-1 sec-1. The reaction 2Ni+ -* Ni + Ni2+ was not observed under these conditions. Nickel formation is attributed to the attack of radicals on the organic nickel compounds. These compounds can be oxidized by H2O2 with rate constants of 104-106 M-1 sec-1. They react slowly with water, the lifetime being somewhat less than 1 sec in the cases of methanol and ethanol and longer in the other cases. Only the •CH2C(CH3)2OH radical does not form a complex but is rapidly reduced to yield isobutene. The complex formed from Ni+ and CO2-rapidly picks up a proton.

Chloride / Bromide / Aqueous solution / Pulse radiolysis / Oxidation / Radical anions / EquilibriumSummary. The oxidation of Br − by Cl 2 − is investigated by gamma pulse radiolysis in aqueous solutions of NaCl and NaBr. Depending on the ratio of the concentration of Br − to Cl − , the main product being observed is either Cl 2 − , ClBr − or Br 2 − . The mixed radical anion ClBr − exhibits a broad absorption band at 350 nm with ε 350 = 9300 dm 3 mol −1 cm −1 . The rate constants of the equilibrium Cl 2 − + Br − ⇔ ClBr − + Cl − are determined to be k f = 4 × 10 9 dm 3 mol −1 s −1 and k b = 1.1 × 10 2 dm 3 mol −1 s −1 . The formation of the Cl 3 − (λ max = 220 nm), Cl 2 Br − (λ max = 230 nm) and ClBr 2 − (λ max = 245 nm) ions in the radiation-chemical oxidation of Cl − and Br − ions in an aqueous solution was observed by pulse radiolysis, and its mechanisms of appearance and the equilibrium constants were determined.

In y-irradiated aqueous CdS04 solutions containing alcohols or formate ions, the hydrated electron reacts with Cd2+ to form Cd+ and the OH and H radicals react with the organic solute to form organic free radicals. The 100 eV yield of metallic cadmium was 2.5 in the presence of formate and close to zero in the presence of t-butanol and in the absence of organic additives. In the presence of other alcohols, the highest yield observed was with methanol [G(Cd) = 1.31 and the lowest with propan-2-01 (G = 0.4).Pulse radiolytic studies with optical absorption, conductimetric and light scattering techniques for detection of intermediates yielded the following results : Cd+ is oxidized by the radical CH2(CH&-COH. a-Alcohol r a d i d s react with Cd+ ions to form products which hydrolyse in the millisecond time scale to regenerate CdZ+. The reaction 2 Cd++Cdq+ (2k = 3 . 0 ~

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