Barium Dichromate, BaCr₂O₇

Barium Dichromate, BaCr₂O₇, is obtained in the anhydrous condition by heating together moist barium chromate and chromium trioxide; it crystallises in slender needles, and is decomposed by water into chromic acid and barium chromate. It is also prepared by heating a mixture of barium chloride and chromium trioxide. The dihydrate, BaCr₂O₇.2H₂O, is obtained by concentration of a solution of barium chromate in chromic acid; it yields yellowish-brown rhombic crystals:

a:b:c = 0.5838:1:1.293.

On heating to 120° C. the crystals become anhydrous.