Publication costs assisted by the French Atomic Energy CommissionThe formation of CI2by pulse radiolysis and its subsequent disappearance, in the presence and absence of N20, have been studied with neutral LiCl solutions of concentrations up to 14 M. In deaerated solutions, the yield with respect to the total absorbed dose shows a maximum at about 9 M, where G(Cl2~) = 3.4, and decreases at higher concentrations. This would seem to indicate that the direct effect on the Clions gives rise to almost no CI2-, while the yield of primary species responsible for its formation (H20 radiolysis) would appear to be about 4.7.

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.

Publication costs assisted by Commissariat a i'Energie AtomiqueThe radical SO^(or HS04) produced by the direct effect of radiation on sulfuric acid has been observed in aqueous 0.4, 2, and 4 M sulfuric acid in yields given by G(SC>4-) = 4.3/(H2S04), where /(H2SO4) is the electron fraction of sulfuric acid present, A reaction scheme is proposed to explain the disappearance of S04-.

Trichloromethyl radicals (h,,, < 230 nm, E,,, . , = 2300 f 450 M -' cm-I) are formed by the pulse radiolysis of aqueous carbon tetrachloride solutions. At concentrations of the order of M and p H 5.5-12.4, CC13 disappears by a second-order process with 2k = (7.4 + 1.8)x lo8 M -I s-I and without detectable hydrolysis. Both CCI, and CHCI, are believed to b e formed by the pulse radiolysis of aqueous chloroform solutions but at wavelengths greater than 230 nm only absorption attributable to CCI, was observed.Les radicaux trichloromtthyles (h,,, < 230 nm, E , ,~ n m = 2300 f 450 M -I cm-I) sont formes par la radiolyse a impulsion des solutions aqueuses The reactions of photochemically produced trichloromethyl radicals have been studied extensively in the gas phase (1) and, to a lesser extent, in organic solvents but have received little attention in aqueous media, where hydrolysis may be one of the processes involved. Trichloromethyl radicals can be produced in aqueous solution by the radiolysis of carbon tetrachloride solutions (2), taking advantage of the efficient reaction between aliphatic chlorine compounds and hydrated electrons (3), Dichloromethyl radicals will be formed via the corresponding reaction with chloroform,The present paper describes the pulse radiolysis of aqueous carbon tetrachloride solutions and reports absorption in the 230-280 nm region which is attributed to CCI,. The decay of the absorbing species from 2 to 90 ps after the pulse is consistent with CCI, dimerization without hydrolysis. Pulse radiolysis of aqueous chloroform solutions appears to produce the same absorbing species, which decays by a second-order process but more 'On leave from the Department of Chemistry and Chemical Engineering, University of Saskatchewan, Saskatoon, Saskatchewan, 1972-1973 rapidly than when formed by the radiolysis of CCI, solutions. ExperimentalSaturated solutions were prepared by shaking reagent grade carbon tetrachloride (Prolabo) or chloroform (Merck) with triple-distilled water (discarding the first five washings) and were purged with argon saturated with the solute and water vapor. Solutions were irradiated as described previously (5) in 2.5 or 5 mm thick silica cells (optical path length, 2.5 cm) by 12 ns pulses of 1.8 MeV electrons from a modified (6) Febetron 707. The system included a Zeiss M4 QIII prism monochromator for which the scattered light a t 230-300nm was less than 0.1% (makers specification, confirmed by experiment). At 230 nm with a slit width of 0.9 mm (the largest used) the bandwidth of the monochromator was 2.3 nm. Absorbed dose (5-100 krad per pulse) was estimated using 0.1 M potassium ferrocyanide solutions saturated with nitrous oxide taking E = 600 M -' cm-I at 440 nm (7) and G = 5.5 (8) for ferricyanide. Results Absorption spectra of transient species presentin 5 x lo-, M CCl, solutions (initial pH 5.5) -30 ns (curve A ) and 2 ps (curve B) after an electron pulse are plotted in Fig. 1. The absorption spectrum of hydroxyl radicals (9) formed during the pulse (Go, = 2.75), assumin...

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