Sodium tungstate

Sodium tungstate ;
Names:	sodium tungstate;
Formula:	Na2WO4 (anhydrous); Na2WO4 · 2H2O (dihydrate);
Molar mass:	293.816 g/mol (anhydrous); 329.846 g/mol (dihydrate);
Density:	4.18 g/cm3 (anhydrous); 3.25 g/cm3 (dihydrate);
Crystal system:	orthorhombic (anhydrous); α=90°, β=90°, γ=90°; orthorhombic (dihydrate); α=90°, β=90°, γ=90°;
Shapes:	https://en.crystalls.info/w/uploads/media/b/bc/Rhombic_prism.json Rhombic prism https://en.crystalls.info/w/uploads/media/5/52/Needle.json Needle ;
Color:	colorless;
Melting point:	698 °C971.15 K <br />1,288.4 °F <br />1,748.07 °R <br /> (anhydrous);
Decomposition point:	1200 °C1,473.15 K <br />2,192 °F <br />2,651.67 °R <br /> (anhydrous);
Stability:	stable (anhydrous);
Hardness:	fragile;
Toxicity:	moderately toxic; LD50=240mg/kg

Description

Salt of alkaline metal sodium and tungstic acid. From water solutions crystallizes as dihydrate.

Precursors

Dissolving tungsten(VI) oxide in melted sodium hydroxide or carbonate

Chemical equation:

NaOH + WO₃ = Na₂WO₄ + H₂O

NaCO₃ + WO₃ = Na₂WO₄ + CO₂

For preparation of 100.00g of sodium tungstate

dihydratedihydrate
anhydrous

а 12.13g of sodium hydroxide or 25.16g of sodium carbonate and 70.29g of tungsten(VI) oxide is required.

Add to the fireproof ceramic or graphite crucible a reagent mixture and heat it until it become melted with occasional stirring. After the reaction will stop, cool the crucible and separate compound.

Dissolving metal tungsten in melted mixture of sodium nitrate and sodium hydroxide

Chemical equation:

W + 3NaNO₃ + 2NaOH = Na₂WO₄ + 3NaNO₂ + H₂O

For preparation of 100.00g of sodium tungstate

dihydratedihydrate
anhydrous

а 24.25g of sodium hydroxide, 77.30g of sodium nitrate and 55.74g of tungsten is required.

Add to the fireproof ceramic or graphite crucible a reagent mixture and heat it until it become melted with occasional stirring. After the reaction will stop, cool the crucible and separate compound.Add to the flask with prepared compound solution small parts of sulfuric acid solution and stir. The large amount of poorly soluble precipitate will form. Settle it out and wash it from soluble impurities few times.Add to flask with hot concentrated solution of alkali small amount of precipitate from previous step with intense stirring. Heat it to 100°C for few minutes for reaction completion and then filter out.

Solubility

TableGraph

Temperature	g/`100,00` g water
0°C273.15 K <br />32 °F <br />491.67 °R <br />	`57.5`
25°C298.15 K <br />77 °F <br />536.67 °R <br />	`74.2`
40°C313.15 K <br />104 °F <br />563.67 °R <br />	`77.9`
80°C353.15 K <br />176 °F <br />635.67 °R <br />	`90.1`
100°C373.15 K <br />212 °F <br />671.67 °R <br />	`96.6`

Slightly soluble in ammonia. Insoluble in ethanol.

Gallery

Tungstates
Sodium tungstate (Na₂WO₄)

Sodium compounds
Salts	Sodium acetate (NaCH₃COO) • Sodium bromide (NaBr) • Sodium citrate (Na₃C₃H₅O(COO)₃) • Sodium chlorate (NaClO₃) • Sodium chloride (NaCl) • Sodium cyclamate (C₆H₁₂NNaO₃S) • Sodium decavanadate (Na₆V₁₀O₂₈) • Sodium ethilate (NaC₂H₅O) • Sodium glutamate (NaC₅H₈NO₄) • Sodium hydrocarbonate (NaHCO₃) • Sodium hydrosulfate (NaHSO₄) • Sodium iodide (NaI) • Sodium metavanadate (NaVO₃) • Sodium niobate (NaNbO₃) • Sodium nitrate (NaNO₃) • Sodium oxalate (Na₂C₂O₄) • Sodium para-aminosalicylate (C₇H₆NNaO₃) • Sodium perchlorate (NaClO₄) • Sodium saccharinate (C₇H₄NaNO₃S) • Sodium sulfate (Na₂SO₄) • Sodium sulfide (Na₂S) • Sodium tetraborate (Na₂B₄O₇) • Sodium thiosulfate (Na₂S₂O₃) • Sodium trichloroacetate (NaCCl₃COO) • Sodium trioxalatoaluminate (Na₃[Al(C₂O₄)₃]) • Sodium tungstate (Na₂WO₄)
Double salts	Potassium-sodium tartrate (KNaC₄H₄O₆) • Sodium-ammonium sulfate (NaNH₄SO₄) • Uranyl-sodium acetate (NaUО2(CH₃COO)₃) • Uranyl-zinc-sodium acetate (NaZn(UO₂)₃(CH₃COO)₉) • Zinc-sodium sulfate (Na₂Zn(SO₄)₂)
Adducts	Glucose and sodium bromide adduct (2C₆H₁₂O₆ · NaBr) • Glucose and sodium chloride adduct (2C₆H₁₂O₆ · NaCl) • Urea and sodium chloride adduct (CO(NH₄)₂ · NaCl)
Complex compounds	Sodium dicarbonatocuprate(II) (Na₂[Cu(CO₃)₂]) • Sodium dioxalatocuprate(II) (Na₂[Cu(C₂O₄)₂]) • Sodium ethylenediaminetetraacetate-ferrate(III) (Na[Fe((OOCCH₂)₂N(CH₂)₂N(CH₂COO)₂)]) • Sodium hexacyanoferrate(II) (Na₄[Fe(CN)₆]) • Tripotassium-sodium hexacyanoferrate(II) (K₃Na[Fe(CN)₆]) • Sodium hexafluorosilicate (Na₂[SiF₆]) • Sodium nitroprusside (Na₂[Fe(CN)₅NO]) • Sodium trioxalatochromate(III) (Ns₃[Cr(C₂O₄)₃]) • Dipotassium-sodium trioxalatoferrate(III) (K₂Na[Fe(C₂O₄)₃]) • Potassium-sodium trioxalatoferrate(III) (K₅Na[Fe(C₂O₄)₃]₂) • Sodium trioxalatoferrate(III) (Na₃[Fe(C₂O₄)₃])

Sodium tungstate
Names:	sodium tungstate
Formula:	Na₂WO₄ (anhydrous) Na₂WO₄ · 2H₂O (dihydrate)
Molar mass:	293.816 g/mol (anhydrous) 329.846 g/mol (dihydrate)
Density:	4.18 g/cm³ (anhydrous) 3.25 g/cm³ (dihydrate)
Crystal system:	orthorhombic (anhydrous) α=90°, β=90°, γ=90° orthorhombic (dihydrate) α=90°, β=90°, γ=90°
Shapes:	Rhombic prism Needle
Color:	colorless
Melting point:	698 °C971.15 K <br />1,288.4 °F <br />1,748.07 °R <br /> (anhydrous)
Decomposition point:	1200 °C1,473.15 K <br />2,192 °F <br />2,651.67 °R <br /> (anhydrous)
Stability:	stable (anhydrous)
Hardness:	fragile
Toxicity:	moderately toxic LD₅₀=240mg/kg