Collect. Czech. Chem. Commun. 1990, 55, 1686-1690

Selective determination of tantalum in ores by extraction with N-phenylbenzohydroxamic acid in toluene

José Aznarez, Juan Carlos Vidal and Cecilia Vaquero

Department of Analytical Chemistry, University of Zaragoza, 50009-Zaragoza, Spain


A method for tantalum(V) spectrophotometric determination in a non-aqueous phase is proposed. Tantalum(V) is extracted with N-phenylbenzohydroxamic acid into toluene from a 5M hydrochloric acid solution. The colour is then developed by addition of 4-(2-pyridylazo)-resorcinol (PAR) solution in N,N-dimethylformamide and pyridine to an aliquot of the extracted phase. The Ta(V)-PAR complex gives an absorption maximum at 547 nm with a molar absorptivity of 3.88 ± 0.04 . 104 l mol-1 cm-1. The method has been applied to the selective determination of tantalum in ores with good accuracy and precision.