Ammonium heptamolybdate

Ammonium heptamolybdate is the inorganic compound whose chemical formula is (NH4)6Mo7O24, normally encountered as the tetrahydrate.

[1] Ammonium heptamolybdate is easily prepared by dissolving molybdenum trioxide in an excess of aqueous ammonia and evaporating the solution at room temperature.

This method results in the formation of six-sided transparent prisms of the tetrahydrate of ammonium heptamolybdate.

Potassium heptamolybdate, also obtained as the tetrahydrate, is very similar to the ammonium salt.

[1] Phosphate test aka Deniges' method links to here.

NFPA 704 four-colored diamond Health 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g. chloroform Flammability 0: Will not burn. E.g. water Instability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogen Special hazards (white): no code
The salt contains the heptamolybdate hexaanion.