Bismuth Chromite, 3Bi₂O₃.2Cr₂O₃

Bismuth Chromite, 3Bi₂O₃.2Cr₂O₃, is prepared by heating bismuth oxychloride with chromium trioxide and water for several hours. It is a brown powder which is insoluble in water, in acids (including aqua regia) and in alkalis.

Many chromates and dichromates of bismuth have from time to time been described, but all except two are probably mixtures. These two compounds may be obtained by the action of chromic acid upon bismuth trioxide. If the concentration of the acid exceeds 7.8 moles per litre the substance Bi₂O₃.4CrO₃ is obtained as a stable salt; if the concentration falls below that figure, this salt is hydrolysed and the substance Bi₂O₃.2CrO₃ is obtained. The former is an orange-scarlet powder and is perhaps a mixed dichromate and chromate, Bi₂Cr₂O₇(CrO₄)₂; the latter is a basic salt, and is obtained as an orange- yellow powder. It may also be prepared by the action of potassium chromate or dichromate on a nearly neutral solution of bismuth nitrate.