Photochemical reduction of 12-molybdoarsenic acid in aqueous-organic media

A photochemical reduction of 12-arsenomolybdic acid (AMA) in water-dioxan (DO), water-tetrahydrofuran (THF) and water-dimethylformamide (DMFA) media has been studied under the action of ultra-violet radiation. Effect of temperature, pH, and radiation time on the reduction process has been studied and optimum conditions are found for all the three media. To elucidate the role of the organic solvent, solvation numbers are determined. The greatest solvation number(4) has been found for the water-DMFA system, for water-DO the solvation number has been found to be 2.2 and for water-THF 0.8. In the range 20-50 deg temperature does not affect the reduction. A method has been proposed of determination of arsenic in the presence of 100-fold molar quantities of silicon using photochemical reduction of AMA in water-DO medium