Effect of Photolytically Generated Hydroxyl Radicals on the Nucleation of Ammonium Chloride from Aqueous Solution

Abstract

THE initiation of condensation in supersaturated vapours by ionizing radiation is, of course, well known as the basic process of the cloud chamber, and the detection of radiation by tracks of ice crystals in supercooled water has also been reported recently¹. There have been few reports of analogous effects in supersaturated solutions although Samuiacas² reported that X-irradiation enhanced the nucleation of sulphur and phosphorus from supersaturated solutions in carbon disulphide. The possibility of similar effects in aqueous solutions was suggested as a result of work carried out by Skinner, Difford and Spencer in the Agricultural Division of ICI (private communication). They observed the effect of low intensities of γ-radiation on the number of crystals formed in the precipitation of sparingly soluble salts such as barium sulphate from aqueous solution, and suggested that the radiolysis products of water were responsible for the effects they observed and that the OH radical was possibly the most potent species. Hydroxyl radicals can be generated profusely by the ultraviolet photolysis of hydrogen peroxide and we have carried out a preliminary investigation of the effect of a high concentration of OH radicals produced in this way on the nucleation of ammonium chloride from aqueous solution.