Extraction and spectrophotometric determination of zirconium(IV) with N-phenylbenzohydroxamic acid and phenylfluorone

Abstract

N-Phenylbenzohydroxamic acid reacted with zirconium(IV) in 3.5 M hydrochloric acid to give a colourless complex that could be extracted into chloroform. The chloroform extract of the zirconium(IV) complex, on a second extraction from a dilute hydrochloric acid medium (0.5 M) in the presence of phenylfluorone and acetone, formed an intensely coloured complex with an absorption maximum at 534 nm. The molar absorptivity under optimum conditions was 1.125 × 10⁴ dm³ mol^–1 cm^–1. The system obeyed Beer's law up to 7 p.p.m. of zirconium(IV) in the extract. Large amounts of many cations and anions, including a ten-fold molar excess of vanadium(IV), iron(III) and molybdenum(VI), were tolerated. Equimolar amounts of aluminium(III), fluoride, phosphate and vanadium(V) were also tolerated. A slight interference from titanium(IV) and niobium(V) was observed when the mole ratio of zirconium(IV) to foreign ion exceeded 1.0 : 0.3. The method was applied successfully to the determination of zirconium(IV) in zircon sand.