Ammonium heptamolybdate

Ammonium heptamolybdate

Names
IUPAC name Ammonium docosaoxoheptamolybdate(6–)
Other names Ammonium molybdate Ammonium paramolybdate (see text)
Identifiers
CAS Number	12027-67-7 Y 12054-85-2 (tetrahydrate) N
3D model (Jmol)	Interactive image
ChemSpider	23786 Y
ECHA InfoCard	100.031.553
EC Number	234-320-9
PubChem CID	71306766
UNII	21Y68J178E Y
InChI InChI=1S/7Mo.6H3N.24H2O/h;;;;;;;6*1H3;24*1H2 Y Key: QGAVSDVURUSLQK-UHFFFAOYSA-N Y InChI=1/7Mo.6H3N.24H2O/h;;;;;;;6*1H3;24*1H2 Key: QGAVSDVURUSLQK-UHFFFAOYAC
SMILES [NH4+].[NH4+].[NH4+].[NH4+].[NH4+].[NH4+].[O-][Mo](=O)(=O)[O-].[O-][Mo](=O)(=O)[O-].[O-][Mo](=O)(=O)[O-]
Properties
Chemical formula	(NH4)6Mo7O24
Molar mass	1163.9 g/mol 1235.86 g/mol (tetrahydrate)
Appearance	white to yellow-green crystalline solid
Density	2.498 g/cm3
Melting point	~90 ˚C (loses water molecule) 190 °C (decomp.)
Solubility in water	43 g/100 ml (tetrahydrate)
Hazards
Main hazards	Irritant
Safety data sheet	External MSDS
NFPA 704	0 2 0
Flash point	Non-flammable
Related compounds
Other anions	Ammonium orthomolybdate Ammonium dimolybdate
Other cations	Potassium paramolybdate
Related compounds	Molybdenum(VI) oxide Molybdic acid
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N  (what is YN ?)
Infobox references

Ammonium heptamolybdate is the inorganic compound, normally encountered as the tetrahydrate, whose chemical formula is (NH₄)₆Mo₇O₂₄·4H₂O. It is a colorless solid, often referred to as ammonium paramolybdate or simply as ammonium molybdate, although "ammonium molybdate" can also refer to ammonium orthomolybdate, (NH₄)₂MoO₄, and several other compounds. Potassium heptamolybdate, also obtained as the tetrahydrate, is very similar to the ammonium salt.

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.

Solutions of ammonium paramolybdate react with acids to form molybdic acid and an ammonium 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. All Mo centers are octahedral. Some oxide ligands are terminal, some doubly bridging, and a few are triply bridging ligands.

Ammonium paramolybdate is harmful if swallowed or inhaled. It causes irritation to the eyes, skin, and respiratory tract. It affects kidneys and blood.

Phosphate test aka Deniges' method links to here.