Ammonium metavanadate explained

Ammonium metavanadate is the inorganic compound with the formula NH₄VO₃. It is a white salt, although samples are often yellow owing to impurities of V₂O₅. It is an important intermediate in the purification of vanadium.^[1]

Synthesis and structure

The compound is prepared by the addition of ammonium salts to solutions of vanadate ions, generated by dissolution of V₂O₅ in basic aqueous solutions, such as hot sodium carbonate. The compound precipitates as a colourless solid.^{[2] [3]} This precipitation step can be slow.

The compound adopts a polymeric structure consisting of chains of [VO₃]⁻, formed as corner-sharing VO₄ tetrahedra. These chains are interconnected via hydrogen bonds with ammonium ions.^[4]

Uses

Vanadium is often purified from aqueous extracts of slags and ore by selective precipitation of ammonium metavanadate. The material is then roasted to give vanadium pentoxide:^[1]

2 NH₄VO₃ → V₂O₅ + 2 NH₃ + H₂O

Other

Vanadates can behave as structural mimics of phosphates, and in this way they exhibit biological activity.^{[5] [6]}

Ammonium metavanadate is used to prepare Mandelin reagent, a qualitative test for alkaloids.

Notes and References

1. Günter Bauer, Volker Güther, Hans Hess, Andreas Otto, Oskar Roidl, Heinz Roller, Siegfried Sattelberger "Vanadium and Vanadium Compounds" in Ullmann's Encyclopedia of Industrial Chemistry, 2005, Wiley-VCH, Weinheim.
2. G. Brauer "Ammonium Metavanadate" in Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY. Vol. 1. p. 1272.
3. Robert H. Baker, Harry Zimmerman, R. N. Maxson "Ammonium Metavanadate" Inorganic Syntheses, 1950, Vol. 3, 117-118.
4. Vladimír Syneček and František Hanic . The crystal structure of ammonium metavanadate . 1954 . Czechoslovak Journal of Physics . 4 . 120–129 . 10.1007/BF01687750 . 2. 1954CzJPh...4..120S . 97890604 .
5. Korbecki, Jan; Baranowska-Bosiacka, Irena; Gutowska, Izabela; Chlubek, Dariusz "Biochemical and medical importance of vanadium compounds" Acta Biochimica Polonica 2012, vol. 59, pp. 195-200.
6. Crans, D. C.; Chatterjee, P. B. "Vanadium Biochemistry" Reedijk, Jan; Poeppelmeier, Kenneth, Eds. Comprehensive Inorganic Chemistry II (2013), 3, 323-342.