title: Extractive separation and spectrophotometric determination of tungsten as phosphotungsten blue.
abstract: Phosphotungsten blue is produced by tin(II) reduction of tungstate solution complexed with phosphate at a w/w ratio of W/P = 5, in 4M hydrochloric acid medium, and extracted with isoamyl alcohol; thus tungsten is separated from Fe(III), Ni, Co, Cr(III), V(V), As(V), Sb(III), Bi, Si, U(VI), Ca and Cu(II). In presence of bismuth (0.5 mg/ml), 99.7% W is separated in a single extraction. After alkaline back-extraction, tungsten is determined spectrophotometrically as phosphotungsten blue; it is measured at 930 nm in aqueous solution or at 900-960 nm after isoamyl alcohol extraction, the Beer's law ranges being 0.08-0.6 and 0.16-0.72 mg/ml respectively. The methods are shown to give satisfactory results in the analysis of practical samples containing some milligrams of tungsten.
authors.affiliation: Department of Chemistry, B.N. Chakravarty University, Kurukshetra 132119, Haryana, India.
authors.forename: V
authors.initials: V
authors.lastname: Yatirajam
authors.forename: S
authors.initials: S
authors.lastname: Dhamija