Mercuric Dichromate, HgCr₂O₇

Mercuric Dichromate, HgCr₂O₇, is obtained as a light orange powder from a solution of the chromate in chromic acid, the concentration of the solution at 25° C. being greater than 10.46 gram-molecules of chromic acid per litre. It forms deep carmine-red crystals.

The compounds, Hg(NH₃)₂CrO₄.H₂O and (OHg₂NH₂)Cr₂O₇.3(NH₄)₂Cr₂O₇.2H₂O, have been described, as also have compounds with pyridine and the double salt, 2NH₂HgCl.HgCrO₄.