Determination of tin and arsenic in ferrotungsten and tungsten ore by iodide extraction method.

Abstract

A rapid spectrophotometric determinati on fo Sn and As in ferrotungsten using solvent extraction has been carried out as follows.Take up 0.5 g of sample with hydrogen peroxide water and hydrofluoric acid, and evaporate to fumes with sulfuric acid. Add, after cooling, an amount of Be2+ and EDTA solution. Neutralize with ammonia water, and then add 10 ml in excess. Boil for 12 min., allow to cool and filter. Dissolve the precipitate with 10N sulfuric acid, and transfer the solution into a separatory funnel. Add potassium iodide solution and benzene, and extract Sn and As by shaking for 2 min. After washing the benzene layer with mixture of sulfuric acid and potassium iodide solution, back-extract Sn and As by shaking with 0.8N sulfuric acid, and made up to 50 ml. For the determination of Sn, add to an aliquot sodium sulfite, the buffer solution, gum arabic and phenylfluorone solution, and measure the absorbance at 510 mμ. For the determination of As, add potassium permanganate, ammonium molybdate solution and hydrazine sulfate solution, and heat in a boiling water bath. Measure the absorbance at 850 mμ.The method is applicable equally for tungsten ores, provided that the sample is taken up with sodium peroxide.