 | |
 | |
| Names | |
|---|---|
| IUPAC name Sodium molybdate | |
| Other names Disodium molybdate | |
| Identifiers | |
| |
3D model (JSmol) | |
| ChEBI | |
| ChemSpider |
|
| ECHA InfoCard | 100.028.683 |
| EC Number |
|
| RTECS number |
|
| UNII |
|
| |
| |
| Properties | |
| Na2MoO4 | |
| Molar mass | 205.92 g/mol (anhydrous) 241.95 g/mol (dihydrate) |
| Appearance | White powder |
| Density | 3.78 g/cm3, solid |
| Melting point | 687 °C (1,269 °F; 960 K) |
| 84 g/100 ml (100 °C) | |
Refractive index (nD) | 1.714 |
| Hazards | |
| NFPA 704 (fire diamond) | |
| Flash point | Non-flammable |
| Lethal dose or concentration (LD, LC): | |
LD50 (median dose) | 4000 mg/kg (rat, oral)[1] |
LC50 (median concentration) | >2080 mg/m3 (rat, 4 hr)[1] |
| Safety data sheet (SDS) | External MSDS |
| Related compounds | |
Otheranions | Sodium chromate Sodium tungstate |
Othercations | Ammonium molybdate |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Sodium molybdate, Na2MoO4, is useful as a source ofmolybdenum.[2] This white, crystalline salt is often encountered as the dihydrate, Na2MoO4·2H2O.
Dissolution ofMoO3 insodium hydroxide at 50–70 °C followed by crystallizing the filtered product.[3] If crystallized below 10 °C, the decahydrate forms. Above 10 °C, the dihydate crystallizes. The anhydrous salt is obtained by heating this product at 100 °C.
The agriculture industry uses 500 tons per year as a fertilizer. In particular, its use has been suggested for treatment of whiptail inbroccoli andcauliflower in molybdenum-deficient soils.[4][5] However, care must be taken because at a level of 0.3 ppm sodium molybdate can cause copper deficiencies in animals, particularly cattle.[3]
It is used in industry forcorrosion inhibition, as it is a non-oxidizing anodic inhibitor.[3] The addition of sodium molybdate significantly reduces the nitrite requirement of fluids inhibited with nitrite-amine, and improves the corrosion protection of carboxylate salt fluids.[6] In industrial water treatment applications wheregalvanic corrosion is a potential due to bimetallic construction, the application of sodium molybdate is preferred oversodium nitrite. Sodium molybdate has the advantage in that the dosing of lower ppm's of molybdate allow for lower conductivity of the circulating water. Sodium molybdate at levels of 50-100 ppm offer the same levels of corrosion inhibition as sodium nitrite at levels of 800+ ppm. By utilizing lower concentrations of sodium molybdate, conductivity is kept at a minimum and thus galvanic corrosion potentials are decreased.[7]
When treated withsodium borohydride, molybdate is reduced tomolybdenum(IV) oxide:[8]
Sodium molybdate reacts with the acids of dithiophosphates:[3]
with R = Me, Et
which further reacts to form [MoO3(S2P(OR)2)4].
In aqueous solution, sodium molybdate features dissociated sodium ions and tetrahedral molybdate (MoO2−4), which adopts asulfate-like structure. The solid dihydrate material has a complex structure typical for alkali metal salts of oxyanions. TheMoO2−4 subunits are tetrahedral with Mo-O distances near 178pm.[3][9]
Sodium molybdate supports the biosynthesis of molybdoenzymes, which are found in all higher forms of life.[10] TheLC50 for freshwater fish ranges from 60 to 7630 mg/L. The toxicity of soluble molybdate to marine organisms has also been reported.[11]
