Chromium Tungstates

The paratungstate, Cr₂O₃.7WO₃.H₂O, is prepared by mixing solutions of ammonium paratungstate and chromic chloride, and drying at 100° C. the resulting greyish-green precipitate; or by treating a cold solution of sodium paratungstate with violet chromic chloride. The green chromic chloride produces a basic salt. The following compounds have been described: Cr₂O₃.5WO₃, Cr₂O₃.5WO₃.5H₂O, Cr₂O₃.4WO₃.6H₂O, Cr₂O₃.3WO₃.3H₂O, Cr₂O₃. 2WO₃.5H₂O, but these appear to be either identical with the paratungstate, or mixtures of the para- and meta-salts.