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prepared originally by reducing the chloride with potassium, and this process, or some modification of it, was the only one available until a few years ago. Moissan prepared “cast uranium ” by submitting an intimate mixture of the oxide and sugar charcoal, contained in a coke crucible, to the electric current. He isolated a crystallized carbide (CAU) whose melting point is much higher than that of platinum, and he prepared samples of the metal containing less than 1 per cent. of impurities. On this latter metal and other samples prepared by the electrolysis of the double uranium-sodium chloride (UCI, 2 NaCl) he determined some of its properties. Ferro-uranium alloys are formed by the last-mentioned process when iron electrodes are used. The metal and some of its alloys have been prepared by various modified forms of the alumino-thermic process: the author, however, found this method to yield poor and very uncertain results. Pure uranium is a white non-magnetic metal, and can be easily filed; it does not scratch glass, is easily carbonized, and may be tempered. Its specific gravity is said to be about 18-7, but the carbonized metal usually met with has a specific gravity of about 12 only. When in fine powder the metal burns at a comparatively low tempera ture (170° in pure oxygen), and also very readily combines with nitrogen. It tarnishes on exposure to air, and also decomposes water to some extent, particularly if heated.
Metallic uranium is decomposed by dilute hydrochloric acid, but black flocks of carbide persist until a few drops of nitric acid have been added. With ferro-uranium alloys or uranium steels it is advisable to filter off this black residue, ignite, fuse it with sodium carbonate, dissolve the melt in hydrochloric acid, and add it to the main solution. The simultaneous precipitation of uranium and separation of iron is made in the manner already described. Carbon in metallic uranium is determined by simple ignition in a stream of oxygen, the resulting carbon dioxide being collected and weighed. The determination of the remaining impurities which affect the value of the metal or alloy for steel-making purposes is made by the usual processes, with which uranium does not interfere.
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