Extraction-spectrophotometric determination of molybdenum with N-m-tolyl-N′-p-chlorophenyl-o-chlorobenzamidine hydrochloride and thiocyanate

Abstract

The reactions of seven amidines with molybdenum(V) in the presence of thiocyanate have been investigated. The molar absorptivities of the reagents lie in the range 1.6 × 10⁴–1.8 × 10⁴ l mol^–1 cm^–1. Of these, N-m-tolyl-N′-p-chlorophenyl-o-chlorobenzamidine hydrochloride is the most sensitive, with a molar absorptivity of 1.8 × 10⁴ l mol^–1 cm^–1 and a Sandell sensitivity of 0.005 µg cm^–2 of molybdenum(V). The method is both sensitive and selective and is free from interference from metal ions commonly associated with molybdenum in various ores and minerals. The colour system obeys Beer's law in the concentration range 0.4–5.6 p.p.m. of metal per 25 ml at 470 nm. The applicability of the method has been confirmed by applying it to the determination of molybdenum in Bhilai Steel samples, a British Chemical Standard steel and dust obtained from phosphate fertilisers.