Barium Dichromate, BaCr₂O₇

Barium Dichromate, BaCr₂O₇, is obtained by heating together solid chromic acid and moist, freshly precipitated barium chromate mixed with potassium chromate and potassium dichromate, or by boiling freshly precipitated barium chromate with chromic acid and nitric acid, or, finally, by decomposing the chromate with dilute sulphuric acid. It crystallises in slender, yellowish-brown, rhombic prisms as BaCr₂O₇.2H₂O, the 2 molecules of water being lost at about 100° C. Barium dichromate is decomposed by water, giving the chromate.