Molybdophosphites

If an acidified solution of ammonium molybdate is warmed with phosphorous acid, a light yellow crystalline precipitate of the ammonium salt, (NH₄)₂[HP(Mo₂O₇)₃]2H₂O, is formed, the reaction forming a delicate test for the presence of phosphorous acid. The sodium salt, Na₂[HP(Mo₂O₇)₃].11H₂O, is slightly more soluble. It loses all its water at 110° C. The potassium, lithium, and guanidinium salts have been prepared.

Conductivity measurements show that these salts are derived from an acid which, like phosphorous acid, is dibasic, and must therefore contain the anion