Radiation Chemistry of Solutions: I. Use of Leuco Triarylmethane Compounds for Chemical Dosimetry

The effects of gamma -radiation on acidic aqueous solutions of a number of 4,4'-thenylidene bisSTAN,N-dimethylaniline! compounds are described. The effects of pH, acid solvent, leuco concentration, added salts, and dissolved oxygen have been investigated. The most sensitive stable system prepared consisted of 10/sup -4/M 4,4'-(5chloro-2-thenylidene)bisSTAN,Nidimethylaniline!, 10/sup -4/ M ferrous ammonium sulfate, 0.1 M sodium chloride, and 7 x 10/sup -3/ M hydrochloric acid. With this system a minimum dose of about 250 rads can be detected by visual observation of color change in a cell with path length of 1 cm. The optical density at the main absorption peak of 633 m mu increases linearly with increasing gamma -ray doses from 0 to at least 2000 rads, and doses is low as 20 rads can be measured with a spectrophotometer with 10-cm cells. With the described experimental conditions, no postirradiation effects such as fading of the dye have been observed. Solutions can be stored in the dark for about 2 weeks prior to use, with littie change in blank readings. (auth)