Ammonium orthomolybdate is the

inorganic compound In chemistry, an inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds, that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as '' inorganic chemist ...

with the chemical formula (NH₄)₂MoO₄. It is a white solid that is prepared by treating molybdenum trioxide with aqueous ammonia. Upon heating these solutions, ammonia is lost, to give ammonium heptamolybdate ((NH₄)₆Mo₇O₂₄·4H₂O).

Uses

Ammonium orthomolybdate is used as a corrosion inhibitor and is an intermediate in some schemes to win molybdenum from its ores.Roger F. Sebenik et al. "Molybdenum and Molybdenum Compounds" in Ullmann's Encyclopedia of Chemical Technology 2005; Wiley-VCH, Weinheim. It is also used for decorating ceramics, and for colorimetric analysis of phosphates and arsenates.

Chemical reactions

Heating ammonium orthomolybdate solid or treatment with acid gives molybdenum trioxide. Such reactions proceed via ammonium dimolybdate. This equilibrium is exploited in the purification of molybdenum from its ores. Aqueous solutions of ammonium orthomolybdate react with

hydrogen sulfide Hydrogen sulfide is a chemical compound with the formula . It is a colorless chalcogen-hydride gas, and is poisonous, corrosive, and flammable, with trace amounts in ambient atmosphere having a characteristic foul odor of rotten eggs. The unde ...

to give ammonium tetrathiomolybdate: : (NH₄)₂MoO₄ + 4 H₂S → (NH₄)₂MoS₄ + 4 H₂O It reacts with arsenic acid upon heating to form a canary yellow precipitate of ammonium α-Keggin molybdoarsenate. : (NH₄)₂MoO₄ + H₃AsO₄ → (NH₄)₂ s(Mo₃O₁₀)₄+ 21 NH₄NO₃ + 12 H₂O

References

Ammonium compounds Molybdates {{inorganic-compound-stub