CERIUM, in chemistry, a new metal obtained from a fossil found in Sweden, to which has been given the name of Ce rite. This fossil occurs disseminated or massive ; it is of a flesh red colour, more or less deep, with sometimes a shade of yellow: it is semitransparent: its fresh fracture has considerable lustre. It strikes fire with steel with difficulty : is not at tracted by the magnet : its specific gra vity is from 4.7 to 4.9. Exposed to a strong heat it does not melt, but loses 5 or 6 per cent. of weight, becomes friable, and ac quires a bright yellow colour. With bo. rax it forms a globule, greenish while hot, but colourless when cold. From 100 parts of it, the Swedish chemists obtained about 50 of oxide of cerium, 22 oxide of iron, 23 silex, and 5.5 carbonate of lime. Ac cording to Vauquelin's analysis, the pro portions are, oxide of cerium 63, silex 17.5, oxide of iron 2, lime from 3 to 4, water 12. The pure oxide of cerium is extracted from the cerite, by dissolving this mineral in nitrornuriatic acid, and, af ter saturating the clear solution with an alkali, precipitating by tartrate of pot ash. The precipitate, well washed, cal cined, and digested in vinegar, is the ox ide of cerium.
The oxide of cerium exists in different degrees of oxidizement. When precipi tated from its acid solutions by the alka lies, it is white, but acquires a shade of yellow when dried in the air, and, when exposed to a continued heat, becomes of a brick red colour. The white, according to Vauquelin, is the one at the lower de gree of oxidizement ; but the difference in the proportion of oxygen is, he remarks, inconsiderable. Neither of them can be fused by heat. Borax determines their fusion : the globule, heated by the exte rior flame of the blowpipe, is of a blood red colour, which, by cooling, becomes of a yellowish green, and, at length, colour less and transparent ; or, if the propor tion of oxide has been large, opaque and pearly.
The metal itself; in the trials which Vauquelin made with it, proved insoluble in any unmixed acid, and was dissolved with great difficulty in nitro-muriatic acid. Its oxide, however, combines with the acids easily, and the properties of its salts have been fully determined.