Radiation Chemistry of Liquid Sulfur Dioxide. II. Radiation-Induced Oxidation—Reduction Reactions in Liquid Sulfur Dioxide Solutions of Sulfur Trioxide and Potassium Iodide

Abstract

Irradiation by 60Co gamma rays of dilute solutions of sulfur trioxide in anhydrous, air-free liquid sulfur dioxide confirms that (1) molecular oxygen is formed by attack of radicals on sulfur trioxide, most likely via O+SO3→SO2+O2, (2) no measurably significant amount of O2 is formed by radical recombination O+O→O2 in the spurs. Irradiation of air-free anhydrous solutions of potassium iodide in liquid sulfur dioxide yields iodine and potassium bisulfate K2S2O7 at constant rates and to high percents of conversion of iodide to iodine. The data are discussed in terms of electron-transfer reactions from the charge-transfer complex iodide anion—sulfur dioxide to the oxygen atom. The possibility of reactions of iodide ion with ionic species which have been suggested to arise in liquid sulfur dioxide during radiolysis is considered briefly. The difference between the radiation chemistry of liquid sulfur dioxide on one hand and those of water and liquid ammonia on the other is believed to be a consequence of the radical scavenging properties of liquid sulfur dioxide.