The anode glow discharge electrolysis was carried out in aqueous sulfuric acid solution, and the yields of oxidation products, H202, H2SO.~, and H2S208, were examined in various atmospheric gases, H2, He, N2, and Ar. When the vapor pressure of water was suppressed by means of intermittent electrolysis, the yields of the peroxides were found to depend clearly on the atmospheric gases. The plasma diagnostics, emission spectra, double-probe method, etc., revealed that the plasma state in the gas phase depended on the gases that contained significant amounts of water vapor. Comparing the oxidation yields with the results on the plasma diagnostics, it was found that (i) the radical formation in the gas phase does