Zuoqian Li, R. Hanrahan
1994
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Abstract
Effects of aging (for ca. 2 days to 2 months) of 1.0 mmolar sodium hexachloroiridate(III) solutions prior to gamma irradiation were studied as a function of added HCl or NaCl concentration. Solutions were irradiated either in air or saturated with N2 . Although fresh solution is readily oxidized to IrClg ", as shown by a strong absorption at 488 nm, aged, neutral solution showed little radiolytic coloration, presumably due to decay of the chloro complex to a chloroaquo complex. A time/concentration dependent "recovery" of the ability of iridium chloride complex to be oxidized to the (IV) state was demonstrated by allowing the solutions to stand prior to irradiation for 1 — 8 days after addition of various amounts of HCl with or without added NaCl. The time to maximum radiolytic sensitivity was 6—7 days using 4 M HCl but only 3 4 days with 6 8 M HCl. Addition of NaCl with HCl enhanced reformation of the hexachloro complex. Alternatively, addition of a few drops of conc. HCl to hexachloroiridate solutions post-irradiation revealed that Ir(III) complex had been oxidized, probably to a chloroaquo form of the (IV) state, provided the solution had not stood more than a few days prior to irradiation. Little post-irradiation color formation was seen in solutions aged for several weeks.