X-Ray Dosimetry by Radiolysis of Some Organic Solutions: I. Dithizone and Methyl Yellow Solutions

Abstract

The selection of a radiation-sensitive system for dosimetric purposes involves a number of problems. If an individual received 600 of total-body irradiation, he would not survive the lethal effects of this dosage (1). Therefore, in order for a system to be of use as a dosimeter, it must be sensitive to dosages in the range 0 to 1000 r. However, most of the known radiation-induced reactions are not affected by such low dosages, and the addition of sensitizers might be employed to make a given reaction useful for dosimetric purposes. Other possibilities include the formation of chain initiators, such as free radicals, which would start a chain reaction, like polymerization, or else the formation of minute quantities of a substance by irradiation which would catalyze a reaction between two other constituents present in the system being irradiated. Aside from high sensitivity to radiation, other properties of a system used as a dosimeter include: temperature, energy and dosage rate independence, stability toward light and heat, and a direct proportionality between dosage and the amount of chemical change. In many systems, especially aqueous systems, minute concentrations of impurities cause large deviations in the proportionality between dosage and chemical change, and stabilizers have to be added to minimize this effect. This disadvantage is not so pronounced in nonaqueous systems, and, in addition, Dainton (2) states that in some respects the investigation of nonpolar liquids offers a better opportunity for elucidating the general principles of radiation chemical changes than work in water or aqueous solutions. On the practical side, a dosimeter employing a nonaqueous system could function at lower temperatures (below 00C) than could an aqueous-system dosimeter. In view of the above-mentioned advantages, solutions of some organic indicators and dyes in organic liquids, mainly chlorinated hydrocarbons, were investigated for their radiation sensitivity, and some were found to be well suited for quantitative estimation of dosages. Although investigations of the chemical effects of X-rays and other ionizing