Sodium molybdate

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Sodium molybdate
Sodium molybdate
Natriummolybdaat.png
Sodium-molybdate-dihydrate-xtal-3D-vdW-labelled.png
Identifiers
CAS number 7631-95-0 YesY
10102-40-6 (dihydrate)
PubChem 61424
EC number 231-551-7
ChEBI CHEBI:75215 N
RTECS number QA5075000
Jmol-3D images Image 1
Properties
Molecular formula Na2MoO4
Molar mass 205.92 g/mol (anhydrous)
241.95 g/mol (dihydrate)
Appearance White powder
Density 3.78 g/cm3, solid
Melting point 687 °C (1,269 °F; 960 K)
Solubility in water 84 g/100 ml (100 °C)
Refractive index (nD) 1.714
Hazards
MSDS External MSDS
EU Index Not listed
NFPA 704
Flammability code 0: Will not burn. E.g., water Health code 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g., chloroform Reactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g., liquid nitrogen Special hazards (white): no codeNFPA 704 four-colored diamond
Flash point Non-flammable
Related compounds
Other anions Sodium chromate
Sodium tungstate
Other cations Ammonium molybdate
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
 N (verify) (what is: YesY/N?)
Infobox references

Sodium molybdate, Na2MoO4, is useful as a source of molybdenum.[1] It is often found as the dihydrate, Na2MoO4·2H2O.

The molybdate(VI) anion is tetrahedral. Two sodium cations coordinate with every one anion.[2]

History[edit]

Sodium molybdate was first synthesized by the method of hydration.[3] A more convenient synthesis is done by dissolving MoO3 in sodium hydroxide at 50–70 °C and crystallizing the filtered product.[2] The anhydrous salt is prepared by heating to 100 °C.

MoO3 + 2NaOH + H2O → Na2MoO4·2H2O

Uses[edit]

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.[4][5] However, care must be taken because at a level of 0.3 ppm sodium molybdate can cause copper deficiencies in animals, particularly cattle.[2]

It is used in industry for corrosion inhibition, as it is a non-oxidizing anodic inhibitor.[2] 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.[6]

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 that 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.[7]

Reactions[edit]

When reacted with sodium borohydride, molybdenum is reduced to a lower valent oxide:[8]

Na2MoO4 + NaBH4 + 2H2O→ NaBO2 + MoO2 + 2NaOH+ 3 H2

Sodium molybdate reacts with the acids of dithiophosphates:[2]

Na2MoO4 + (RO)2PS2H (R = Me, Et) → [MoO2(S2P(OR)2)2]

which further reacts to form [MoO3(S2P(OR)2)4].

Safety[edit]

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.[9]

References[edit]

  1. ^ Greenwood, Norman N.; Earnshaw, Alan (1984). Chemistry of the Elements. Oxford: Pergamon Press. ISBN 0-08-022057-6. 
  2. ^ 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.
  3. ^ Spitsyn, Vikt. I.; Kuleshov, I. M. Zhurnal Obshchei Khimii 1951. 21. 1701-15.
  4. ^ Plant, W. (1950). "Use of Lime and Sodium Molybdate for the Control of ‘Whiptail’ in Broccoli". Nature 165 (4196): 533. doi:10.1038/165533b0. 
  5. ^ Davies, E. B. (1945). "A Case of Molybdenum Deficiency in New Zealand". Nature 156 (3961): 392. doi:10.1038/156392b0. 
  6. ^ Vukasovich, Mark S. Lubrication Engineering 1980. 36(12). 708-12.
  7. ^ M. Houser, Corrosion Control Services, Inc., Introduction Handbook
  8. ^ Chi Fo Tsang and Arumugam Manthiram. Journal of Materials Chemistry 1997. 7(6). 1003–1006.
  9. ^ http://www.mallbaker.com/americas/msds/english/s4394_msds_us_default.pdf

External links[edit]