The spectrophotometric determination of tungsten with thiocyanate. Part III. Moderating the interference by molybdenum in the determination of tungsten in steel

Molybdenum in excess of 0·3 per cent. w/w interferes in the determination of tungsten in low tungsten steels (W < 0·25 per cent. w/w) with thiocyanate because of a molybdenum-iron inter-element effect. Two procedures are described which overcome this limitation. In the first procedure tungsten(VI) and molybdenum(VI) are extracted into chloroform as benzoin α-oxime complexes prior to the determination of tungsten. In the second procedure iron is extracted from the tungsten and molybdenum into isobutyl methyl ketone. Up to 4 and 25 per cent. w/w, respectively, of molybdenum in the steel can be tolerated when these procedures are used.