Bismuth Molybdates

Specimens of native bismuth molybdate containing metallic bismuth have been observed in Saxony. The normal salt Bi₂(MoO₄)₃ is obtained as a lemon-yellow precipitate on adding a solution of bismuth nitrate to potassium molybdate solution. It dissolves in water, 1 part of the salt in 500 parts of water, and also in acids. It crystallises in the tetragonal form with a:c = 1:1.5636, the crystals resembling those of lead molybdate, and having density 6.07 at 15° C. The melting-point of bismuth molybdate is 643° C.

Under certain conditions bismuth may be quantitatively precipitated from a weak nitric acid solution by means of excess of ammonium paramolybdate, in the form of bismuth ammonium molybdate, Bi(NH₄)(MoO₄)₂.