Some Effects of Heavy-Particle Irradiation of Aqueous Acetic Acid

Abstract

In the preceding papers of this symposium, consideration has been given to the problem of determining the mechanism of the decomposition of water by highenergy radiation. Formation of the chemically reactive radicals H and OH and the decomposition products H2 and H202 have been critically investigated in the light of available evidence. According to present concepts (1-5) of the mechanism of the indirect action of radiation on solutes, the preliminary chemical effect is the dissociation, by ionization and excitation, of water molecules to give the H and OH radicals. The observed chemical changes in irradiated solutions are attributed to subsequent reactions of H and OH radicals with one another and with solute molecules. The relative amounts of those radicals that combine to form H2 and H202 and of those that are available for reaction with added solute depend upon the ionization density of the effective radiation. Radiation chemical reactions in dilute solution have been discussed in the previous papers in some detail, primarily however, from the standpoint of determining the yields of free H and OH. In studies of this type, in which the principal objective is the determination of the mechanism of water decomposition, the use of relatively simple solute systems is advantageous because the complete mechanism of the over-all reaction must be determined. Radiolysis of most aquo-organic systems, however, usually results in the formation of a spectrum of reaction products many of which may be formed in amounts which are difficult, if not impossible, to determine by classical analytical procedures. The development of radiometric and chromatographic techniques during the last few years has made it possible to study quantitatively many of the systems which were previously not amenable to investigation. Recently, as part of a general investigation (6-8) of radiation-induced reactions of organic substances in aqueous solution, we have applied these techniques to a study of the products formed in aqueous acetic acid by heavy-particle irradiation. Some of the methods and results are described in the present paper.