Sodium tungstate explained

Sodium tungstate is the inorganic compound with the formula Na₂WO₄. This white, water-soluble solid is the sodium salt of tungstic acid. It is useful as a source of tungsten for chemical synthesis. It is an intermediate in the conversion of tungsten ores to the metal.

Preparation and structure

Sodium tungstate is obtained by digestion of tungsten ores, the economically important representatives of which are tungstates, in base. Illustrative is the extraction of sodium tungstate from wolframite:

Fe/MnWO₄ + 2 NaOH + 2 H₂O → Na₂WO₄·2H₂O + Fe/Mn(OH)₂Scheelite is treated similarly using sodium carbonate.

Sodium tungstate can also be produced by treating tungsten carbide with a mixture of sodium nitrate and sodium hydroxide in a fusion process which overcomes the high exothermicity of the reaction involved.

Several polymorphs of sodium tungstate are known, three at only one atmosphere pressure. They feature tetrahedral orthotungstate dianions but differ in the packing motif. The anion adopts a structure like sulfate .^[1]

Reactions

Treatment of sodium tungstate with hydrochloric acid gives the tungsten trioxide or its acidic hydrates:

Na₂WO₄ + 2 HCl → WO₃ + 2 NaCl + H₂O

Na₂WO₄ + 2 HCl → WO₃·H₂O + 2 NaCl This reaction can be reversed using aqueous sodium hydroxide.

Uses

The dominant use of sodium tungstate is as an intermediate in the extraction of tungsten from its ores, almost all of which are tungstates. Otherwise sodium tungstate has only niche applications.

In organic chemistry, sodium tungstate is used as catalyst for epoxidation of alkenes and oxidation of alcohols into aldehydes or ketones. It exhibits anti-diabetic effects.^[2]

Solutions of sodium and lithium metatungstates are used in density separation. Such solutions are less toxic than bromoform and methylene iodide, but still have densities that fall between a number of naturally coupled minerals.^[3]

Sodium tungstate is a competitive inhibitor of molybdenum; because tungsten is directly below molybdenum on the periodic table, it has similar electrochemical properties. Dietary tungsten reduces the concentration of molybdenum in tissues.^[4] Some bacteria use molybdenum cofactor as part of their respiratory chain; in these microbes, tungstate can replace molybdenum and inhibit the generation of energy by aerobic respiration. As such, one niche use of sodium tungstate is in experimental biology—where it has been found that adding sodium tungstate to the drinking water of mice inhibits the growth of Enterobacteriaceae (a family of endogenous opportunistic pathogens) in the gut.^[5]

Sodium tungstate has been researched as a potential treatment for infertility under the code OXO-001.^{[6] [7] [8]}

Further reading

• Altirriba J, Barbera A, Del Zotto H, Nadal B, Piquer S, Sánchez-Pla A, Gagliardino JJ, Gomis R . Molecular mechanisms of tungstate-induced pancreatic plasticity: a transcriptomics approach . BMC Genomics . 10 . 406 . August 2009 . 19715561 . 2741493 . 10.1186/1471-2164-10-406 . free .

Notes and References

1. Pistorius CW . Phase diagrams of sodium tungstate and sodium molybdate to 45 kbar. . The Journal of Chemical Physics . June 1966 . 44 . 12 . 4532–4537 . 10.1063/1.1726669 . 1966JChPh..44.4532P .
2. Domínguez JE, Muñoz MC, Zafra D, Sanchez-Perez I, Baqué S, Caron M, Mercurio C, Barberà A, Perona R, Gomis R, Guinovart JJ . The antidiabetic agent sodium tungstate activates glycogen synthesis through an insulin receptor-independent pathway . The Journal of Biological Chemistry . 278 . 44 . 42785–42794 . October 2003 . 12925525 . 10.1074/jbc.M308334200 . free .
3. Skipp GL, Brownfield IK . Improved density gradient separation techniques using sodium polytungstate and a comparison to the use of other heavy liquids. . US Geological Survey . 1993 .
4. Book: Molybdenum. 2005. Van Nostrand's Encyclopedia of Chemistry. 1038–1040. New York. Wiley-Interscience. 978-0-471-61525-5. Considine GD .
5. Zhu W, Winter MG, Byndloss MX, Spiga L, Duerkop BA, Hughes ER, Büttner L, de Lima Romão E, Behrendt CL, Lopez CA, Sifuentes-Dominguez L, Huff-Hardy K, Wilson RP, Gillis CC, Tükel Ç, Koh AY, Burstein E, Hooper LV, Bäumler AJ, Winter SE . Precision editing of the gut microbiota ameliorates colitis . Nature . 553 . 7687 . 208–211 . January 2018 . 29323293 . 5804340 . 10.1038/nature25172 . 2018Natur.553..208Z .
6. Canals I, Cotán D, Torres R, Horcajadas JA, Arbat A . Sodium tungstate increases embryo adhesion through a direct effect on endometrial cells. . Human Reproduction . 2021 . 36 . Supplement_1 . deab130.402 . 10.1093/humrep/deab130.402.
7. Arbat A, Gonzalez-Bulnes A, Pérez-Villalobos N, Canals I . Oral administration of sodium tungstate to a swine model improves embryo implantation rate. . Human Reproduction . 2021 . 36 . Supplement_1 . 10.1093/humrep/deab130.355 .
8. Web site: Fertility drug could lead to 7% increase in live births after IVF, trials show. . Devlin H . The Guardian . 7 July 2024 .