3D model (JSmol)
CompTox Dashboard (EPA)
|Molar mass||205.92 g/mol (anhydrous)|
241.95 g/mol (dihydrate)
|Density||3.78 g/cm3, solid|
|Melting point||687 °C (1,269 °F; 960 K)|
|84 g/100 ml (100 °C)|
Refractive index (nD)
|NFPA 704 (fire diamond)|
|Lethal dose or concentration (LD, LC):|
LD50 (median dose)
|4000 mg/kg (rat, oral)|
LC50 (median concentration)
|>2080 mg/m3 (rat, 4 hr)|
|Safety data sheet (SDS)||External MSDS|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Sodium molybdate, Na2MoO4, is useful as a source of molybdenum. This white, crystalline salt is often found as the dihydrate, Na2MoO4·2H2O.
The molybdate(VI) anion is tetrahedral. Two sodium cations coordinate with every one anion.
Sodium molybdate was first synthesized by the method of hydration. A more convenient synthesis is done by dissolving MoO3 in sodium hydroxide at 50–70 °C and crystallizing the filtered product. The anhydrous salt is prepared by heating to 100 °C.
- MoO3 + 2NaOH + H2O → Na2MoO4·2H2O
The agriculture industry uses 1 million pounds per year as a fertilizer. In particular, its use has been suggested for treatment of whiptail in broccoli and cauliflower in molybdenum-deficient soils. However, care must be taken because at a level of 0.3 ppm sodium molybdate can cause copper deficiencies in animals, particularly cattle.
It is used in industry for corrosion inhibition, as it is a non-oxidizing anodic inhibitor. The addition of sodium molybdate significantly reduces the nitrite requirement of fluids inhibited with nitrite-amine, and improves the corrosion protection of carboxylate salt fluids. In industrial water treatment applications where galvanic corrosion is a potential due to bimetallic construction, the application of sodium molybdate is preferred over sodium nitrite. Sodium molybdate has the advantage in that the dosing of lower ppm's of molybdate allow for lower conductivity of the circulating water. Sodium molybdate at levels of 50-100 ppm offer the same levels of corrosion inhibition as sodium nitrite at levels of 800+ ppm. By utilizing lower concentrations of sodium molybdate, conductivity is kept at a minimum and thus galvanic corrosion potentials are decreased.
When reacted with sodium borohydride, molybdenum is reduced to lower valent molybdenum(IV) oxide:
- Na2MoO4 + NaBH4 + 2H2O → NaBO2 + MoO2 + 2NaOH + 3H2
Sodium molybdate reacts with the acids of dithiophosphates:
- Na2MoO4 + → [MoO2(S2P(OR)2)2]
which further reacts to form [MoO3(S2P(OR)2)4].
Sodium molybdate is incompatible with alkali metals, most common metals and oxidizing agents. It will explode on contact with molten magnesium. It will violently react with interhalogens (e.g., bromine pentafluoride; chlorine trifluoride). Its reaction with hot sodium, potassium or lithium is incandescent.
- ^ a b "Molybdenum (soluble compounds, as Mo)". Immediately Dangerous to Life or Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
- ^ Greenwood, Norman N.; Earnshaw, Alan (1984). Chemistry of the Elements. Oxford: Pergamon Press. ISBN 978-0-08-022057-4.
- ^ a b c d e Braithwaite, E.R.; Haber, J. Molybdenum: An outline of its Chemistry and Uses. 1994. Elsevier Science B.V. Amsterdam, The Netherlands.
- ^ Spitsyn, Vikt. I.; Kuleshov, I. M. Zhurnal Obshchei Khimii 1951. 21. 1701-15.
- ^ Plant, W. (1950). "Use of Lime and Sodium Molybdate for the Control of 'Whiptail' in Broccoli". Nature. 165 (4196): 533. Bibcode:1950Natur.165..533P. doi:10.1038/165533b0. S2CID 4213274.
- ^ Davies, E. B. (1945). "A Case of Molybdenum Deficiency in New Zealand". Nature. 156 (3961): 392. Bibcode:1945Natur.156..392D. doi:10.1038/156392b0. S2CID 4071159.
- ^ Vukasovich, Mark S. Lubrication Engineering 1980. 36(12). 708-12.
- ^ M. Houser, Corrosion Control Services, Inc., Introduction Handbook
- ^ Tsang, Chi Fo; Manthiram, Arumugam (1997). "Synthesis of lower-valent molybdenum oxides in aqueous solutions by reducing Na2MoO4 with NaBH4". Journal of Materials Chemistry. 7 (6): 1003–1006. doi:10.1039/A606389F. ISSN 1364-5501.
- ^ http://www.mallbaker.com/americas/msds/english/s4394_msds_us_default.pdf[permanent dead link]