Sodium tungstate: Difference between revisions

| Verifiedfields = changed

| Watchedfields = changed

| verifiedrevid = 440185222

| ImageFile=Wolframan_sodný.JPG

| ImageSize=

| IUPACName=Sodium tungstate

| OtherNames=

| CASNo_Ref = {{cascite|correct|CAS}}

| UNII_Ref = {{fdacite|correct|FDA}}

| UNII = 64LRH4405G

| PubChem= 26052

| RTECS= YO7875000

| InChI = 1S/2Na.4O.W/q2*+1;;;2*-1;

| SMILES= [O-][W](=O)(=O)[O-].[Na+].[Na+]

| Formula = Na₂WO₄

| MolarMass = 293.82 g/mol

| Appearance=White [[Rhombohedral crystal system|rhombohedral]] crystals

| Density=4.179 g/cm³ (anhydrous) <br> 3.25 g/cm³ (dihydrate)

| MeltingPtC= 698

| BoilingPt=

| Solubility= 57.5 g/100 mL (0 °C) <br> 74.2 g/100 mL (25 °C) <br> 96.9 g/100 mL (100 °C)

| SolubleOther = slightly soluble in [[ammonia]] <br> insoluble in [[ethanol|alcohol]], [[acid]]

|Section3={{Chembox Structure

| CrystalStruct = Rhombic (anhydrous) <br> orthorhombic (dihydrate)

}}

|Section4={{Chembox Hazards

| ExternalSDS = [http://www.sciencelab.com/msds.php?msdsId=9927281 External MSDS]

| MainHazards=

| FlashPt=

| AutoignitionPt =

}}

|Section8={{Chembox Related

| OtherCations = [[Lithium tungstate]]<br/>[[Caesium tungstate]]

'''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 [[ore]]s to the metal.<ref name=Ullmann>{{Ullmann|first1=Erik|last1=Lassner|first2=Wolf-Dieter|last2=Schubert|first3=Eberhard|last3=Lüderitz|first4=Hans Uwe|last4=Wolf |title=Tungsten, Tungsten Alloys, and Tungsten Compounds|doi=10.1002/14356007.a27_229|year=2005}}</ref>

==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]]:<ref name=Ullmann/>

:Fe/MnWO₄ + 2 NaOH + 2 H₂O → Na₂WO₄·2H₂O + Fe/Mn(OH)₂

[[Scheelite]] 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 [[Polymorphism (materials science)|polymorphs]] of sodium tungstate are known, three at only one atmosphere pressure. They feature tetrahedral orthotungstate dianions but differ in the packing motif. The {{chem|WO|4|2−}} anion adopts a structure like sulfate ({{chem|SO|4|2−}}).<ref>Carl W. F. T. Pistorius "Phase Diagrams of Sodium Tungstate and Sodium Molybdate to 45 kbar" J. Chem. Phys. 1966, volume 44, 4532.{{doi|10.1063/1.1726669}}</ref>

==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 [[tungstate]]s.<ref name=Ullmann/> Otherwise sodium tungstate has only niche applications.

In organic chemistry, sodium tungstate is used as catalyst for [[epoxidation]] of [[alkene]]s and oxidation of [[Alcohol (chemistry)|alcohol]]s into [[aldehyde]]s or [[ketone]]s. It exhibits anti-diabetic effects.<ref>[http://www.jbc.org/content/278/44/42785.full.pdf The Antidiabetic Agent Sodium Tungstate Activates Glycogen Synthesis through an Insulin Receptor-independent Pathway]. The Journal of Biological Chemistry, Vol. 278, No. 44, Issue of October 31, pp. 42785–42794, 2003.</ref>

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.<ref>[https://pubs.usgs.gov/of/1992/0386/report.pdf Improved density gradient separation techniques using Sodium Polytungstate and a comparison to the use of other heavy liquids]. Report, U.S. Geological Survey, 1993.</ref>

Sodium tungstate is a [[competitive inhibition|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.<ref name="Nostrand">{{cite book|contribution = Molybdenum|date = 2005|title = Van Nostrand's Encyclopedia of Chemistry|pages = 1038–1040|place= New York|publisher = Wiley-Interscience|isbn=978-0-471-61525-5|editor= Considine, Glenn D.}}</ref> 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.<ref> {{cite journal|title=Precision editing of the gut microbiota ameliorates colitis |year=2018 |pmid=29323293 |pmc=5804340 |last1=Zhu |first1=W. |last2=Winter |first2=M. G. |last3=Byndloss |first3=M. X. |last4=Spiga |first4=L. |last5=Duerkop |first5=B. A. |last6=Hughes |first6=E. R. |last7=Büttner |first7=L. |last8=De Lima Romão |first8=E. |last9=Behrendt |first9=C. L. |last10=Lopez |first10=C. A. |last11=Sifuentes-Dominguez |first11=L. |last12=Huff-Hardy |first12=K. |last13=Wilson |first13=R. P. |last14=Gillis |first14=C. C. |last15=Koh |first15=A. Y. |last16=Burstein |first16=E. |last17=Hooper |first17=L. V. |last18=Bäumler |first18=A. J. |last19=Winter |first19=S. E. |last20=Winter |first20=Sebastian E. |journal=Nature |volume=553 |issue=7687 |pages=208–211 |doi=10.1038/nature25172 |bibcode=2018Natur.553..208Z }}</ref>

{{Reflist}}

* [https://www.sciencedaily.com/releases/2009/08/090827192334.htm The Anti-Diabetic Effects Of Sodium Tungstate Revealed], ScienceDaily, Aug. 28, 2009

{{tungsten compounds}}

[[Category:Tungsten mining]]