Title: Determination of arsenic(III) and arsenic(V) in hot spring waters
Abstract: Arsenic (V) is separated from arsenic (III) by coprecipitation with MgNH4PO4·6H2O at pH 9.0. The precipitate is dissolved in H2SO4 (1 + 5) and HCl(1 + 1) and analyzed for arsenic by silver diethyldithiocarbamate spectrophotometric method. The amount of arsenic (V) is calculated by subtracting arsenic (V) from the total arsenic determined on a separate portion of sample. Large amounts of iron (III) and manganese (II) interfered with the determination of arsenic (V). The oxidation number of arsenic in some typical samples was found to be five.