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| Names | |
|---|---|
| IUPAC name Ammonium docosaoxoheptamolybdate(6–) | |
| Other names Ammonium molybdate Ammonium paramolybdate (see text) | |
| Identifiers | |
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3D model (JSmol) | |
| ChemSpider |
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| ECHA InfoCard | 100.031.553 |
| EC Number |
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| UNII |
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| Properties | |
| (NH4)6Mo7O24 | |
| Molar mass | 1163.9 g/mol 1235.86 g/mol (tetrahydrate) |
| Appearance | white solid |
| Density | 2.498 g/cm3 |
| Melting point | ~90 ˚C (loses water molecule) 190 °C (decomp.) |
| 65.3 g / 100 ml (tetrahydrate) | |
| Hazards | |
| Occupational safety and health (OHS/OSH): | |
Main hazards | Irritant |
| NFPA 704 (fire diamond) | |
| Flash point | Non-flammable |
| Safety data sheet (SDS) | External MSDS |
| Related compounds | |
Otheranions | Ammonium orthomolybdate Ammonium dimolybdate |
Othercations | Potassium paramolybdate |
Related compounds | Molybdenum(VI) oxide Molybdic acid |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Ammonium heptamolybdate is theinorganic compound whosechemical formula is (NH4)6Mo7O24, normally encountered as the tetrahydrate. A dihydrate is also known. It is a colorless solid, often referred to asammonium paramolybdate or simply asammonium molybdate, although "ammonium molybdate" can also refer toammonium orthomolybdate, (NH4)2MoO4, and several other compounds. It is one of the more common molybdenum compounds.[1]
Ammonium heptamolybdate is easily prepared by dissolving molybdenum trioxide in an excess of aqueous ammonia and evaporating the solution at room temperature. While the solution evaporates, the excess of ammonia escapes. This method results in the formation of six-sided transparent prisms of the tetrahydrate of ammonium heptamolybdate.[2]
Solutions of ammonium paramolybdate react with acids to formmolybdic acid and anammonium salt. The pH value of a concentrated solution will lie between 5 and 6.
The compound was first analyzed crystallographically by Lindqvist, but has been reanalyzed.[3] All Mo centers are octahedral. Some oxide ligands are terminal, some doubly bridging, and a few are triplybridging ligands.
Potassium heptamolybdate, also obtained as the tetrahydrate, is very similar to the ammonium salt.[3]
Molybdates are typically of low toxicity, so much so that few reports of incidents have ever been reported.[1]
