Difference of Sodium Tungstate and Sodium Molybdate
The difference between sodium tungstate and sodium molybdate is reflecting in their physical and chemical properties and application, they are two different substances, but because of tungsten and molybdenum belong to the same family of ⅥB, so that there are some similarities in physical and chemical properties , but a lot of differences exist.
Difference of Physical Property
| Name | Sodium Tungstate | Sodium Molybdate |
| Chemical Formula | Na2WO4 | Na2Mo4 |
| Molar Mass | 293.82 g·mol−1 | 205.92 (Anhydrous) g·mol−1 241.95 (Dihydrate) g·mol−1 |
| Density | 4.179 g/cm3 3.23 g/cm3(Dihydrate) |
3.78 g/cm3, solid |
| Appearance | White Diamond Crystal | White Powder |
| Melting Point | 698°C | 687 °C |
| CAS Number | 13472-45-2 10213-10-2(Sodium Tungstate Dihydrate) |
7631-95-0 10102-40-6 (Sodium Molybdate Dihydrate) |
| Solubility (Water) | 74.2 g/100 mL | 84 g/100 ml (100 °C) |
| Solubility (Other Solvents) | Slightly Soluble in Ammonia, Insoluble in Ethanol | Insoluble in Acetone |
Difference of Chemical Property
When sodium tungstate meets strong acid, it will generate tungstic acid precipitation:
Na2WO4+2HCl—Boiling→H2WO4↓(Yellow)+2NaCl
Na2WO4+2HCl+H2O→H2WO4•H2O↓(White)+2NaCl
Sulfur atom will substitute the oxygen atom in tungstate radical one by one when hydrogen sulfide inlets into sodium tungstate solution, and finally generate tetrathiocarbonate sodium tungstate.
Sodium molybdate will react with acid to produce molybdic acid precipitation:
Na2MoO4+2HCl→H2MoO4↓+2NaCl
Difference of Application
Sodium tungstate is the raw material of manufacturing metal tungsten, tungstic acid and tungstate salts; also used as a mordant, catalyst and pigments, as well as fabric fire retardant and chemical analysis reagents ect.; also, it is widely used in industries of petroleum, aerospace and defense.
Sodium molybdate is mainly used as metal corrosion inhibitor, descaling agent, bleaching agent and protective agent of skin and hair; alkaloids, dyes and analytical reagent for pharmaceutical industry.
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