Aluminium molybdate

A white, amorphous precipitate of the composition 5Al₂O₃.2MoO₃.xH₂O is obtained by adding sodium molybdate, Na₂MoO₄, to a solution of alum. The double salts Al₂(Mo₂O₇)₃.3X₂Mo₂O₇, where X is Na, K, or NH₄, are known and possess 22, 20, and 20 molecules of water of crystallisation respectively.