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

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Abstract
Solutions of dithizone (diphenylthiocarbazone) and methyl yellow (p-dimethylaminoa-zobenzene) in CHCl3 and CCl4 were irradiated with X-rays at various concentrations, volumes, dosage rates, energies or voltages, and in the presence of inhibitors and sensitizers. Chemical change was quantitatively evaluated from spectroph-otometric measurements with a Cary instrument. The G values (no. of molecules reacting per 100 ev of absorbed energy), and the M values (no. of molecules reacting per roentgen absorbed) were calculated in all cases. Dithizone is twice as sensitive to X-rays in CCl4 as in CHCl3, independently of concentration, dosage rate, etc. The production of free radicals in the solvents provide an explanation of the mechanism of chemical change. Methyl yellow is more sensitive in CHC13 than in CCl4 since HCl is formed from the solvent, whereas the Cl free atom from CCl4 destroys the conjugated double bond in the indicator molecule. II. Sensitized indicator solutions. Ibid.[long dash]Utilizing the techniques described in I, solutions of 2-hydroxy-4-nitrophenylazo-bieta-p-naphthol and of resaz-urin (diazoresorcinol) in ethanol to which CHCl3 and CCl4 were added as sensitizers were irradiated under various controlled conditions, and the G and M values calculated as before. The 1st solute is 4 times as sensitive to CCl4 as to CHCl3, the free radical mechanism again explaining the mechanism of change. The reverse is true for resazurin. Mixed solutions of the 2 compounds were highly satisfactory for dosimetry of radiation over a wide range of energies and a series of colors from blue to red was calibrated against dose in roentgens.

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