Ammonium Heptamolybdate

Ammonium heptamolybdate is a colorless solid, often referred to as ammonium paramolybdate or simply as ammonium molybdate. It is one of the more common molybdenum compounds.

Ammonium Heptamolybdate is used to prepare high purity grade molybdenum metal powder, sheet, or wire; for colorimetric analysis of phosphates and arsenates; for decorating ceramics; and as catalysts.

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.

Inhalation causes irritation of nose and throat. Contact with eyes causes irritation.

Ammonium Heptamolybdate 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.