Ammonium Uranyl Carbonate, (NH₄)₄UO₂(CO₃)₃

Ammonium Uranyl Carbonate, (NH₄)₄UO₂(CO₃)₃.2H₂O, is obtained by dissolving freshly precipitated ammonium uranate in a solution of ammonium carbonate at 60° to 70° C.; or by treating a soluble uranyl salt with ammonium carbonate and ammonia. In either case a yellow solution is formed which on evaporation deposits yellow monoclinic crystals of the double carbonate. The same compound results on mixing concentrated solutions of ammonium carbonate (3 molecules) and uranyl nitrate (1 molecule) at 50° to 55° C., and allowing to cool. The crystals have density 2.77. They lose ammonia slowly on keeping; rapidly when heated to 130° C., leaving a residue of uranic anhydride. The carbonate dissolves in water, but the solution decomposes on warming. The solubility at 18.6° C. is 6.04 parts of salt in 100 parts of water. Another ammonium salt, (NH₄)₆(UO₂)₂(CO₃)₅.4H₂O, is obtained if ammonium carbonate and uranyl nitrate are mixed in the proportion, (NH₄)₂CO₃, 5 molecules: UO₂(NO₃)₂, 1 molecule. It separates as a yellow crystalline crust.