n-arylhydroxamic acids as reagents for vanadium(v) : Spectrophotometric determination of vanadium(v) with n-m-tolyl-p-methoxybenzohydroxamic acid

A study of the coloured complexes of 51 N-arylhydroxamic acids with vanadium(V) in hydrochloric acid media is described. The absorption spectra of the coloured chloroform extracts and the molar absorptivities are compared. The effects of different substituents attached to the carbon and nitrogen atom of the hydroxamic acid functional group are discussed. A rapid extraction-spectrophotometric method for the determination of vanadium(V) is described, employing the most promising of these reagents, N-m-tolyl-p-methoxybenzohydroxamic acid. The method is highly selective and tolerates large amounts of diverse ions usually associated with vanadium-bearing materials including iron(III), aluminium(III), chromium(III), nickel(II), cobalt(II), zinc(II) and manganese(II).