Extraction-spectrophotometric determination of vanadium in stainless steel and nickel-base alloys with N-benzoyl-N-phenylhydroxylamine

• Published in: Bunseki kagaku Vol. 28; no. 7; pp. 401 - 405
• Main Authors: KAYA, Akira, OHUCHI, Yoshifusa, SAKAI, Fumiaki
• Format: Journal Article
• Language: English
• Published: Tokyo Japan Science and Technology Agency 1979
• ISSN: 0525-1931
• DOI: 10.2116/bunsekikagaku.28.7_401

A simple, rapid, and accurate extraction-spectrophotometric methods has been developed for the determination of vanadium in stainless steel and Ni-base alloys. The procedure is as follows: Take 0.5 g of sample into a beaker and add 20 ml of aqua regia, then heat and dissolve it. Furthermore add 5 ml of perchloric acid, and heat until the sample is dissolved, and add 14 ml of sulfuric acid (1+1) and 5 ml of phosphoric acid. Continue heating untill fumes of sulfuric acid generate from it. Thereafter, transfer it with use of water into a polyethylene separating funnel, add 10 ml of hydrofluoric acid (46%) and dilute to 50 ml with water. Then, add 4 ml of iron(II) ammonium sulfate solution (10%) and mix it thoroughly. Allow to stand for two or three min, and add 10 ml of ammonium peroxysulfate solution (45%) and mix it thoroughly again. By this procedure vanadium is oxidized to vanadium(V) without any oxidation of chromium(III). Allow to stand for about five minutes. Then add exactly 20 ml of N-benzoyl-N-phenylhydroxylamine chloroform solution (0.1%) and shake it vigorously for two min. Then, determine vanadium by measuring absorbance at the wavelength of 530 nm against a chloroform reference. The interference ofchromium can be eliminated by reduction to Cr(III) with iron(II) ammonium sulfate, while manganese and molybdenum do not interfere at 530 nm. In the determination of 100 μg vanadium, the following amounts of foreign ions are tolerated: Fe(III) and Ni 1 g, Cr(III) 500 mg, Al 200 mg, Mo(VI) 100 mg, Mn, Co(II), Ti(IV) and Nb(V) 50 mg, Si 20 mg, Cu 10 mg, Ta(V) and W(VI) 5 mg.