Uranium Carbide, UC₂

Uranium Carbide, UC₂, was first prepared by Moissan by heating together urano-uranic oxide (50 parts) and sugar charcoal (6 parts) in the electric furnace. By employing a current of 900 amperes and 50 volts, the reaction was complete in five minutes, and the fused mass on cooling yielded a lustrous, crystalline solid, of density 11.28 at 18° C. It may also be obtained by fusing the requisite quantities of uranous oxide and carbon in a Ruff electric vacuum furnace. The formula U₂C₃ was given to the product by Moissan, but by careful analysis and metallographic investigation it has been shown that the composition is correctly expressed by the formula UC₂. The carbide is harder than quartz, but not so hard as corundum. It is often pyrophoric, and is readily oxidised; it inflames readily on crushing in an agate mortar, and will emit sparks when merely shaken in a strong glass vessel or when two pieces of the carbide are rubbed together. It melts at a temperature somewhat above 2250° C. It is attacked by fluorine at low temperatures, yielding uranous fluoride, but if a little chlorine is also present, the product is uranic fluoride, UF₆. It reacts with chlorine at 350° C.; with bromine at 390° C.; with iodine below red heat; with nitrogen, yielding nitride, at 1100° C. It burns readily in oxygen at 370° C., forming the green oxide.

Uranium carbide is decomposed by water. The reaction proceeds slowly, and a mixture of solid, liquid, and gaseous hydrocarbons is produced. The gaseous product, which accounts for about one-third of the carbon present, consists of a mixture of the lower paraffin and olefine hydrocarbons, with a little acetylene, and from 30 to 60 per cent, of free hydrogen. The carbide is attacked by dilute mineral acids in the cold; by concentrated acids on warming. Nitric acid decomposes it most readily. Hydrogen chloride and hydrogen sulphide react at about 600° C. Uranium carbide is used as a catalyst in the synthetic production of ammonia.