Uranic Oxide (U2O3) may be obtained in the anhydrous state by heating the hydrated sesquioxide to a temperature of 572° Fahr. The sesquioxide is capable of acting both as an acid and a base. The uranic salts are yellow.
Uranous Oxide. (UO.) This may be procured by igniting uranium oxalate in a closed vessel, or in a stream of hydrogen gas. Acids are without action upon this oxide. When, however, it is obtained as an hydrate (which it may be by treatment of its chloride with ammonia) this latter is easily acted upon by acids, and gives rise to salts having a green colour, which rapidly absorb oxygen. Peligot proposed to call this oxide Uranyl (UO.), from the tendency it showed to follow the deportment of a metal when it combined with elementary bodies.
Chlorides of Uranium. Uranium forms two chlorides, U2Cl3 and UCl2.
Uses. Its ores and oxides are occasionally used to colour glass and enamels.
U′RATES. Salts of uric acid.
U′REA. COH4N2. Syn. Cyanate of ammonium (Anomalous). A crystalline, colourless, transparent substance, discovered by Fourcroy and Vauquelin in urine, and by Wöhler as the first organic compound artificially produced.
Urea generally occurs in slender, striated, colourless prisms, as shown on next page. It is slightly deliquescent. It has a neutral reaction and a bitterish taste. It is extremely soluble in water and in hot alcohol, but very slightly so in ether. At about 248° Fahr. it melts. At a little higher temperature it becomes decomposed into ammonia, carbonate, cyanate of ammonium, and cyanuric acid; this latter being left in the retort.
The ammoniacal odour acquired by urine after a few days is due to the conversion of the urea into carbonate of ammonia, as shown by the following equation:
| Urea. | Water. | Carb. Ammonia. | ||
| CH4ON2 | + | 2H2O | = | (NH4)2CO3. |
This change is effected by the mucus of the bladder present in the urine. A solution of pure urea may be kept at ordinary temperature, or even boiled, without undergoing alteration.