Mercurous Molybdates

When a neutral solution of an alkali molybdate is treated with mercurous nitrate, the molybdenum is completely precipitated in the form of a mercurous molybdate of uncertain composition. The precipitate on ignition is converted to molybdic anhydride, so that the reaction may be used for the estimation of molybdenum. The normal salt, Hg₂O.MoO₃, may be obtained in the form of golden-yellow needles by treating a solution of alkali trimolybdate with mercurous nitrate, and boiling the resulting yellowish-white precipitate with the mother-liquid. If the precipitate is immediately filtered and washed until all volatile matter is removed, the dimolybdate, Hg₂O.2MoO₃, remains.