Barium Vanadates

Barium orthovanadate cannot be separated because on formation it splits up immediately into barium hydroxide and pyrovanadate. Barium pyrovanadate, Ba₂V₂O₇, is obtained by the precipitation of barium chloride by sodium ortho- or pyro-vanadate. It is slightly soluble in water.

Barium metavanadate, BaV₂O₆, is obtained in the form of yellowish transparent crystals, slightly soluble in water, by heating sodium and barium bromide with vanadic acid, or in colourless transparent prisms, insoluble in water, by adding barium nitrate in excess to a boiling solution of ammonium vanadate. A monohydrate, BaV₂O₆.H₂O, is formed as a flocculent, yellowish-white precipitate by the action of the normal potassium or ammonium salt on barium chloride solution. On long standing, or on drying, it becomes crystalline. It loses practically all its water at 180°-200° C. After fusion it solidifies to a brownish-yellow glass.

Certain acid salts are known, 2BaO.3V₂O₅.14H₂O, obtained in orange-red, transparent, rhombic crystals by the action of a boiling solution of ammonium vanadate on excess of barium nitrate in the presence of acetic acid, and 3BaO.5V₂O₅.19H₂O.

Halogen compounds corresponding to the apatites and wagnerites have been obtained.

Barium fluoroxyvanadate, BaF₂.VO₂F, is formed as a heavy, bright yellow, insoluble powder by precipitating barium fluoride with potassium fluoroxy vanadate.