ISO 1618:1976

The method is applicable to products having vanadium contents between 0,0003 % (m/m) and 0,016 % (m/m), provided that the content of chromic oxide and titanic oxide does not exceed 0,002 % (m/m) and 0,006 % (m/m), respectively. The principle consists in a previous oxidation of the vanadium contained in the test sample to vanadium(V) by patassium permanganate in sulphuric acid solution. Formation of the vanadium-N-benzoyl-N-phenylhydroxylamine complex. Extraction of the violet coloured complex with chloroform in hydrochloric acid*solution. Photometric measurement of the coloured complex at a wavelength of about 524 nm.