An apparatus is described which allows one to measure the polarographic currents of free H atoms produced radiation chemically in an aqueous solution under 50 atm of hydrogen. The electrode was a tiny mercury drop. The polarogram of the H-atom contains a weak anodic wave and two cathodic waves. The pH dependence of these waves is described and electrode processes are attributed to the waves.

Methyl and ethyl radicals were also produced in solutions under high methane or ethane pressure as well as the 2-hydroxyethyl radical in an ethylene + N₂O containing solution. All these radicals have separated anodic and cathodic waves. The anodic wave is shifted towards more negative potentials in alkaline solutions. In acid solution additional cathodic currents were obtained in the potential range between the two main waves. Various electrode reactions of these organic radicals are discussed.