The (NH4)2U2O7 is precipitated from an aqueous solution of 10 g of UO2(NO3)2 ? 6 H2O by the addition of a cone. ammonia. The fine yellow powder is suction-filtered, washed with water, and stirred with an excess of cone. (NH4)2CO3 solution for about 10 minutes (the flask is on a 70°C water bath). The clear supernatant liquid is decanted and allowed to stand overnight. Yellow crystals precipitate; these are filtered with suction and dried in air. The residue of undissolved (NH4)2U2O7 is treated several times with the mother liquor at 70°C, as described above until crystals no longer form on cooling.
