Sodium tungstate

Mô tả

The predominant route to this salt is the extraction of tungsten ores, almost all of which are tungstates. Thus, the ores, are treated with base to give sodium tungstate, as illustrated in the case of wolframite:

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 polymorphs of sodium tungstate are known, three at only one atmosphere pressure. They feature tetrahedral orthotungstate dianions but differ in the packing motif. The WO42- anion adopts a structure like sulfate (SO42-).

Sodium tungstate

IUPAC name[hide] Sodium tungstate
Identifiers
CAS number	13472-45-2 Y
PubChem	26052
RTECS number	YO7875000
Jmol-3D images	Image 1
Properties
Molecular formula	Na2O4W
Molar mass	293.82 g mol?1
Appearance	white rhombohedral crystals
Density	4.179 g/cm3 (anhydrous) 3.25 g/cm3 (dihydrate)
Melting point	698 °C, 971 K, 1288 °F
Solubility in water	57.5 g/100 mL (0 °C) 74.2 g/100 mL (25 °C) 96.9 g/100 mL (100 °C)
Solubility	slightly soluble in ammonia insoluble in alcohol, acid
Structure
Crystal structure	rhombic (anhydrous) orthorhombic (dihydrate)
Y (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)

ỨNG DỤNG

For the metal tungsten, tungsten acid and tungstate manufacturing as well as dyes, pigments, inks, such as electroplating.

For fabric and cellulose fire retardant, catalyst, etc.

Keyword:Catalyst;Environmental protection paint

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