Publication costs assisted by Commissariat á I'Energie AtomiqueThe effect of the dielectric constant of the solvent on the reactivity of the solvated electron formed by pulse radiolysis has been studied in water-ethanol mixtures. It was found that the rate constant k(es~+ NOb-) diminishes with decreasing water concentration whereas ¿(es~+ Zn2+) increases in going from pure water to 60% by weight ethanol. On the other hand, k(es~+ H+) is almost invariant with the solvent composition, from pure water to 99% by weight ethanol. From measurements of the rate constant of the very fast reaction es~+ C6HSN02 we have estimated the diffusion coefficient of the solvated electron in water-ethanol mixtures. Using the appropriate equations with the values of the diffusion coefficient of es-thus determined we have shown that it is possible to correlate the rate constants of the reactions between solvated electrons and ions with the macroscopic dielectric constant of the medium. The distance at which reaction takes place is, in each case, approximately equal to the sum of the individual ionic radii.

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time, no spectrum ascribable to the CIO radical can be detected. However, the spectrum of a transitory species whose maximum lies at 310 nm is observed just after the photolytic flash. Working on the reasonable hypothesis that the primary act of photodissociation is 0-C1-0 + hv -* CiO(2ir) + 0(3P), these experimental results are explained in terms of a cage recombination of the photolysis fragments leading to the formation of chlorine atoms and molecular oxygen and a rapid bulk reaction between CIO and CIO2 leading to the species CI2O3. The reaction between Cl (or Cl2~) and CIO2 gives CI2O2, which has an absorption maximum at 310 nm.

SWJWIZU~Y 10:-(cSG0 ca. 1000 M-1 cm-1) ions and 10: cgB0 ca. 3O0Or\.r1 cm-l) radicals are formed by pulse radiolysis of periodate ion in aqueous solution.