Gravimetric determination of tungsten with tetraphenylarsonium chloride after its extraction as thiocyanate.
Small amounts of tungsten in natural and industrial samples can be freed from all important interfering elements by extraction of molybdenum by xanthate, reduction of tungsten by mercury and extraction of tungsten(V) thiocyanate into tribenzylamine, and finally back-extraction. The tungsten can be then determined as tetraphenylarsonium tungstate by precipitating it at pH 2-4, filtering it off and drying it at 110 degrees for 45 min. An overall error of 0.1-0.2% is obtained for 5-60 mg of tungsten.
Yatirajam
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Department of Chemistry, Kurukshetra University, Kurukshetra 132119, Haryana, India.
Dhamija
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