The effect of gamma radiation on some organicpH indicators

The effect of gamma-radiation on the color intensity of a series of representative organic dyes, commonly used as pH indicators, has been studied. In aqueous medium, at commonly used concentration levels, the dyes demonstrate ability to indicate pH after gamma-doses of 10³-10⁴ r. In general all the dyes show less sensitivity to radiation in neutral or basic media than in acid media. The compounds demonstrate a pseudo first order degradation reaction rate which was shown to be the expected radiation effect zero order rate. Of those compounds studied, methyl orange proved to be the most sensitive to radiation while bromocresol green is the most resistant to radiation damage. It was found that addition of small amounts of ethyl alcohol to the medium was effective in decreasing dye radiation damage to a large degree. Research sponsored by the U.S. Atomic Energy Comission under contract with the Union Carbide Corporation.