Pulse radiolysis of the aqueous ferro-ferricyanide system. II. Reactions of hydrogen atoms and e_aq^- with ferrocyanide and ferricyanide ions

Hydrogen atoms react with both ferro- and ferricyanide. The reaction with ferrocyanide, previously unknown, proceeds with a rate constant k(H + Fe(CN)₆^4-) = 4 × 10⁷ M^-1 sec^-1, independent of pH in the range 1-8. This reaction is followed by two consecutive processes, of which the first one is first order, while the second one is a reaction of an intermediate with ferrocyanide ions. Aquapentacyanoferrate(II) was identified as a final product. All the intermediates reacted with ferricyanide. The nature of the reaction products is discussed and the rates of the various processes measured as a function of pH are given. Hydrated electrons react only slowly, if at all, with ferrocyanide ions, k(e_aq^- + Fe(CN)₆^4-) < 7.5 × 10⁴ M^-1 sec^-1. Low yields of aquapentacyanoferrated(II) (∼10%) are produced by reduction of ferricyanide ions by H atoms and e_aq^- at neutral pH.