Reactivity of the hydrated electron and the hydroxyl radical with boric acid in aqueous solutions

The reactivity of the hydrated electron and the hydroxyl radical with boric acid has been investigated by steady-state and pulse radiolytic techniques. No evidence was found for appreciable reactivity with hydroxyl radicals by either method and an upper limit of 5 x 104 dm3 mol-1 s-1 is estimated for the reaction rate constant. Steady-state irradiations gave no evidence for reactivity with the hydrated electron, but pulse-radiolysis experiments showed the hydrated electron decay rate to be linearly dependent on boric acid concentration but independent of pH. Although superficially suggesting a reaction with boric acid it seems more likely that the enhanced decay is due to an impurity in the boric acid (probably nitrate) and an upper limit of 5 x 103 dm3 mol-1 s-1 is estimated for k(e-sub(aq) + H3B03). (author)