Sodium tungstate

Structural formula
General
Surname	Sodium tungstate
other names	Disodium tungstate; Sodium orthotungstate;
Molecular formula	Na 2 WO 4
Brief description	white, odorless crystals
External identifiers / databases
ECHA InfoCard	100.033.389
PubChem	26052
Wikidata	Q418410
properties
Molar mass	293.82 g mol −1 ; 329.85 g mol −1 (dihydrate);
Physical state	firmly
density	4.18 g cm −3 (anhydrous); 3.23 g cm −3 (dihydrate);
Melting point	698 ° C (anhydrous)
solubility	good in water (730 g l −1 at 20 ° C, dihydrate)
safety instructions
GHS labeling of hazardous substances Caution
H and P phrases	H: 302
	P: 264-270-301 + 312-330-501
Toxicological data	1190 mg kg −1 ( LD 50 , rat , oral )
	As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Sodium tungstate (more precisely sodium orthotungstate) is a white, crystalline, readily water-soluble salt from the group of tungstates .

Extraction and presentation

Sodium tungstate is an important intermediate product in the production of tungsten from scheelite (CaWO ₄ ) and wolframite (Fe, MnWO ₄ ) and is obtained by reacting the minerals with NaOH or Na ₂ CO ₃ .

{\ displaystyle \ mathrm {WO_ {3} +2 \ NaOH \ rightarrow Na_ {2} WO_ {4} + H_ {2} O}}

properties

Sodium tungstate also occurs as the dihydrate Na ₂ WO ₄ · 2 H ₂ O, which gives off its water of crystallization at over 100 ° C. Aqueous solutions of sodium tungstate have an alkaline reaction ( pH 9–11.5 at a measuring temperature of 20 ° C and a concentration of 100 g / l).

When an acid is added, sodium tungstate polymerizes and takes on a yellowish color.

use

Like ammonium tungstate, sodium tungstate is used as a catalyst in organic chemistry.

Individual evidence

↑ ^a ^b ^c ^d ^e Entry on disodium tungstate in the GESTIS substance database of the IFA , accessed on February 1, 2016(JavaScript required) .
↑ Entry on sodium tungstate. In: Römpp Online . Georg Thieme Verlag, accessed on June 14, 2014.
↑ ^a ^b ^c Data sheet sodium tungstate dihydrate (PDF) from Merck , accessed on February 28, 2018.
↑ z. B. Patent-de: Catalysts for the production of olefins by oxidative dehydrogenation

[GESTIS-1] Entry on disodium tungstate in the GESTIS substance database of the IFA , accessed on February 1, 2016(JavaScript required) .

[2] Entry on sodium tungstate. In: Römpp Online . Georg Thieme Verlag, accessed on June 14, 2014.

[Merck-3] Data sheet sodium tungstate dihydrate (PDF) from Merck , accessed on February 28, 2018.

[4] z. B. Patent-de: Catalysts for the production of olefins by oxidative dehydrogenation