3808
M. E. LANGMUIR AND E. HAYON
chemical kinetics of react,ions taking place in photochemistry and radiation chemistry. These radicals can be formed by reactlion of S04'-, H2S04, NOa-, or HN03 with OH radicals, or by direct phot'olytic or radiolytic decomposition of these molecules. I n addi-
tion, these radicals once formed can react with other solutes present in solution. A comparison of IC values in Tables I1 and IV shows that HS04 or SO4- is a much stronger oxidizing species than NO3, though it is not as strong as hydroxyl radical.
Flash Photolysis Study of Mercury(I1) Halide Complexes in Aqueous Solution. Rates of Reaction of X; Radical Anions
by M. E. Langmuir and E. Hayon Pioneering Research Dinision, U . S. Army h'atick Laboratories, aVatick, Massachusetts (Receised M a y 5, 1967)
The photochemistry of aqueous solutions of mercury(I1) halide complexes has been studied. The optical spectra of the transient species formed have been observed using the technique of flash photolysis. The complexes HgC12, HgC12-, HgBr2, HgBr42-, and HgT,'- all give rise to the corresponding radical anions C12-, Br2-, and 12-. HgI, produced an intermediate with a maximum at 330 mfi. The decay kinetics of the transient species formed from the different polyhalide complexes have been examined in neutral and acid solutions. The rates of reaction of Cl2- and Brz- with added solutes (methanol, ethanol, isopropyl alcohol, oxalate, and H202)have also been determined in neutral and acid sdutions. 12radical anions are found to be relatively unreactive (ks 10' IM-' sec-' with alcohols). A comparison of the rates of reaction of the inorganic oxidizing radicals OH, SO4-, X03, C12-, Br2-, and 12- with some compounds indicates that the oxidizing power qf these radicals follows the order OH > SO4- > Clz- > YO3 > Br2- >> I,-.
IERc~RY(II) HALIVECOMPLEXES
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