The determination of tantalum by the solvent extraction of a tantalum-pyrogallol complex

Abstract

A colorimetric procedure for determining up to 1·2 mg of tantalum in the presence of up to 20 mg of niobium, or up to 180 mg of tungsten, has been developed. The colourless tantalum-pyrogallol complex is extracted into ethyl acetate at pH between 4·5 to 6·0 by means of tetrahexyl or tetrabutyl ammonium iodide and back-extracted with acidified ammonium oxalate (pH 2·0). The yellow complex obtained is measured spectrophotometrically at 400 mµ.