TPAC-チオシアン酸塩のクロロホルム抽出によるフェロニオブ中タングステン定量法

概要

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One fifth gram of a sample was fused with potassium pyrosulfite and taken up with 50 ml of hydrochloric acid (1+2) containing 2 g of ammonium oxalate. It was diluted to 100 ml with water. To a 10 ml aliquot corresponding to ca. 100 μg of W were added 20 ml of hydrochloric acid and 5 ml of stannous chloride solution (20 w/v% in hydrochloric acid), and the mixture was boiled gently for about 2 min. to reduce tungsten. After cooling, it was transferred by washing with hydrochloric acid to a 200 ml polyethylene separatory funnel, and 5 ml of ammonium hydrogen fluoride solution (20 w/v%) was added as a masking agent for niobium. Each 3 ml of TPAC solution (0.025M) and sodium thiocyanate solution (15 w/v%) was added and shaken well. It was made up to 70 ml with hydrochloric acid and shaken vigorously with accurately 20 ml of chloroform for 2 min. The separated layer of chloroform was filtered through a dried paper, and the amount of tungsten was obtained by measuring absorbance at about 400 mμ. The method was successfully applied to the determination of about 0.5% of tungsten as an impurity in ferro-niobium.
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