Ammonium heptamolybdate

Ammonium heptamolybdate
Names
IUPAC name
Ammonium docosaoxoheptamolybdate(6–)
Other names
Ammonium molybdate
Ammonium paramolybdate
(see text)
Identifiers
12027-67-7 Yes
12054-85-2 (tetrahydrate)
ChemSpider 23786 Yes
EC number 234-320-9
Jmol-3D images Image
PubChem 71306766
UNII 21Y68J178E Yes
Properties
(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.)
43 g/100 ml (tetrahydrate)
Hazards
MSDS External MSDS
Main hazards Irritant
EU Index Not listed
NFPA 704
Flammability code 0: Will not burn. E.g., water Health code 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g., chloroform Reactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g., liquid nitrogen Special hazards (white): no codeNFPA 704 four-colored diamond
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 noted otherwise, data is given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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Infobox references

Ammonium heptamolybdate is an odourless crystalline compound ranging in colour from white to yellow-green. It is usually encountered as the tetrahydrate, whose chemical formula is (NH4)6Mo7O24·4H2O. It is 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.

Synthesis

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.[1]

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.

Uses

Safety

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

References

  1. L. Svanberg & H. Struve, J. pr. Ch. 44 [1848], p. 282; cited in Gmelin's Handbuch für Anorganische Chemie, 53, p. 255.
  2. Parsons, T.; Maita, V. & Lalli, C. (1984). A manual of chemical and biological methods for seawater analysis. Oxford: Pergamon.
  3. Harris, J. R. and Horne, R. W. 1991. "Negative staining", in Harris J. R. (Ed.), Electron Microscopy in Biology, Oxford University Press, Oxford.
  4. Adrian, M.; Dubochet, J.; Fuller, S. D. and Harris, J. R. 1998. "Cryo-negative Staining". Micron 29, p. 145–160; doi:10.1016/S0968-4328(97)00068-1.
  5. De Carlo, S.; El-Bez, C.; Alvarez-Rúa, C.; Borge, J. and Dubochet, J. 2002. "Cryo-negative staining reduces electron-beam sensitivity of vitrified biological particles". J. Struct. Biol. 138, p. 216–226; doi:10.1016/S1047-8477(02)00035-7; PMID 12217660.

See Also

Phosphate test aka Deniges' method links to here.