Determination of arsenic with Michler's thioketone

Michler's thioketone is proposed as the reagent for the spectrophotometric determination of trace arsenic(V). The molar absorptivity of the colored pr oduct of interaction between Michler's thioketone and molybdoarsenic acid i s (1.02 +/-0.04) x 10(5) at 640 nm. A procedure is developed for the extrac tion-photometric determination of arsenic in tap and mineral waters. The ad ded-found method is used. The determination limit of arsenic is 0.003 mg/L; in the concentration range 0.008-0.12 mg/L, the relative standard deviatio n varies from 20 to 8 %.