Studies have been made of the [gamma]-ray-induced reduction of ferric ion in dilute sulfuric acid solutions containing cupric ion and formic acid. By suitable concentration adjustments a set of conditions was found in which the ferrous ion yield gives a direct measure of the sum GH + GOH- The radical scavenging action of increasing concentrations of cupric ion and formic acid was investigated with Co60 [gamma]-rays, and found to be in accord with the predictions of the radical diffusion theory.