330
The Journal of Physical Chemistry, Vol. 83, No. 3, 1979
Pucheault et al.
Radiolysis of Concentrated Solutions. 1. Pulse and y Radiolysis Studies of Direct and Indirect Effects in LiCl Solutions J. Pucheault," C. Ferradlni, R. Julien, A. Deysine, Laboratoire de Chimie-Physique, Universit6 Ren6 Descaries, 45, 75270 Paris, Cedex 06, France
L. Gilles, and M. Moreau DRA-SRIRMa CEN Saclay, 91 190 Gif-sur-Yvette,France (Received February 27, 1978; Revised Manuscript Received September 15, 1978) Publication costs assisted by the French Atomic Energy Commission
This study of the radiolysis of concentrated aqueous LiCl solutions enables the relative contributions of the direct and indirect effects to be evaluated as a function of C1- concentration and also permits an evaluation of the role of C1- in the early stages of water radiolysis. Radicalar and molecular yields Gclz-, GOH, Gee5X
loy2M, for which a plateau of G(NOz-) was observed. If most of the C1, ions were reduced by NOz, G(NOT) would decrease down to 0 for [Cl-] 1 10 M, when GOH = 0. It is the case (Figure 8, curve b) when 2-propanol is used instead of HCOO-;17 2-propanol appears then to be a worse scavenger of Clzthan HCOO-. (d) The yield of the production of COO- (GOH GH Gat-) is always greater than that of NO2 (Ge,-) and its excess disproportionates. It is evident when comparing Figures 8 and 6 that in the opposite case (GeBf> GoH + GH + Gc12-),NOz in excess would disproportionate and curve a of Figure 8 would represent G(N02-) = GoH G H Gel,- + l/z[Ge,g- - (GOH GN Gcl -)] which would be higher than the curve d of Figure 6 (GoH + Gel;). (2) Reduction of Tetranitromethane by ea; and Q2-, Theoretically the second method leads to the determination of Gesp G H . Pulse18J9 and radiolytic studies have shown that the formation of the nitroform anion C(N0J3- produced in aerated aqueous solutions of tetranitromethane, C(N0J4, is due to hydrated electrons eaq-and superoxide ions 02-.For neutral solutions saturated with C(N02)4,the proposed mechanism is i s also negligible for [HCOO-]
5
+ NO3- + 2H+
This method was applied here to aerated LiCl solutions saturated with tetranitromethane. Under these conditions the concentration of C(N02)4varied from 5 to 0.15 x
+
M with increasing [Cl-I. It was verified that results were independent of these changes of concentration of tetranitromethane. In the pulse radiolysis study, the permanent absorption of nitroform a t 320 nm was measured after complete decay of Clz- ( 100 p s ) . As seen on curve c of Figure 9, the results so obtained are slightly higher that those obtained by the preceding method, particularly for the low concentrations of C1-. This difference can be attributed to GH, but unfortunately the experimental errom prevent any accurate determination of this yield by difference. On the contrary, the values of G(C(N02)
