Superoxide and ozone production by corona discharge

Abstract

A modification of the technique used by Bastien and Lecuiller (F. Bastien and M. Lecuiller, J. Chem. Phys., 1973, 70, 1692) has been used to study the chemical products of corona discharge from a negatively charged needle point in nitrogen, subsequently allowed to flow into air and collected in an indirectly earthed aqueous solution. From the behaviour of cytochrome C, methaemoglobin, ceric sulphate, ferrous sulphate and tetranitromethane in such solutions it is concluded that practically all of the negatively charged corona products collected in them are superoxide, of which a fraction dismutates at the solution surface and the remainder reacts with dissolved reagents. The technique has been used in studies of Fe²⁺+ Cu²⁺ mixtures at pH 2 to show that HO₂ reduces Cu²⁺ca. 200 times faster than it oxidises Fe²⁺ and to confirm that the resulting Cu⁺ is oxidised both by oxygen and by Fe³⁺, at rates consistent with those reported in a recent study by less direct methods (E. Bjergbakke, K. Sehested and O. L. Rasmussen, Radiat. Res., 1976, 66, 433). Ozone accompanies superoxide in the discharge in comparable yields per corona ion which are independent of corona voltage, but it does not react significantly with exposed solutions except with very reactive substances such as potassium iodide.