Spectrophotometric determination of hafnium as a mixed-ligand complex with N-p-tolyl-p-methoxybenzohydroxamic acid and xylenol orange

Abstract

A selective and sensitive method for the extraction and spectrophotometric determination of hafnium in microgram amounts based on the formation of the hafnium-N-p-tolyl-p-methoxybenzohydroxamic acid-xylenol orange ternary complex is described. Hafnium is extracted from hydrochloric and perchloric acids with N-p-tolyl-p-methoxybenzohydroxamic acid into chloroform. Xylenol orange solution is subsquently added to the organic phase and the absorbance is measured at 540 nm. The molar absorptivities of the hafnium complexes are 8.40 × 10⁴ and 6.97 × 10⁴ l mol^–1 cm^–1, respectively. Various parameters for optimum extraction and colour development are described.