SPECTROPHOTOMETRIC DETERMINATION OF VANADIUM(V) WITH N-PHENYLCINNAMOHYDROXAMIC ACID

N-Phenylcinnamohydroxamic acid (PCHA) reacts with vanadium(V) to form a 1:2 (V:PCHA) bluish-violet coloured complex, quantitatively extracta ble into chloroform from 3-9 M hydrochloric acid solutions. The spectr um of the complex in the visible region exhibited a broad absorption m aximum at 545 nm with a molar absorptivity of 6300 M(-1) cm(-1). The c oloured system obeyed Beer's law in the concentration range of 0.5-10 mu g ml(-1) of vanadium. The effects of several experimental variables on the extraction of the complex have been studied to establish the o ptimum conditions for the determination of vanadium(V). On the basis o f these studies a simple, precise, and sensitive method has been devel oped for the spectrophotometric determination of vanadium(V). The meth od has been successfully applied to the determination of vanadium in s tandard steels.