Simultaneous spectrophotometric determination of molybdenum and iron with salicylaldehyde thiosemicarbazone, and application to the analysis of steels

Salicylaldehyde thiosemicarbazone reacts with molybdenum(VI) in mineral acid solution, in the presence of stannous chloride, to produce a 1:1 red-violet complex (lambdasub(max)=520 nm, epsilon=4.8x103 l.mole-1.cm-1). Iron (II and III) forms a green 1:2 complex, in ammonia-ammonium chloride solution (lambdasub(max)=590 nm, epsilon=1.7x103 l.mole-1.cm-1). Both complexes have been used with success in the photometric estimation of molybdenum and iron in mixtures. Molybdenum may be determined in presence of 40 times its weight of iron. Iron may be determined in presence of twice its weight of molybdenum. The reagent can be applied to the analysis of steels. The interferences of some metallic ions have been examined