Cerium, a metal which was discovered simultaneously in 1803 by Klaproth, Hisinger, and Berzelius, and was so called by the last named after the planet Ceres. It occurs in association with lanthanum and didymium in cerite, allanite or thite, yttrocerite, and a few other rare minerals. Cerite, containing also lanthanum and didymium, is the most abundant of these minerals. Wohler prepared the metal in the following manner: The brown oxide, obtained by incinerating the oxalate, is dissolved in hydrochloric acid, and the resulting chloride mixed with about equal parts of chloride of potassium and chloride of ammonium, and evaporated to expel all of the ammonia, and finally fused. The slag thus obtained is pulverized, and while still warm is mixed with sodium and projected into a crucible previously heated. The reaction is continued until the soda flame disappears. The cooled mass contains metallic pellets. Cerium has a lustre between iron and lead, and loses its polish in the air. It is malleable, ductile, and soft as lead. Its specific gravity is 5.5 at 12o C. Before the blowpipe it glows to a brown oxide; heated powerfully, it explodes with scintillation.

The pulverized metal takes fire at 100° C. It decomposes water slightly at the boiling point; is rapidly dissolved by I1C1, converted to brown oxide by concentrated nitric acid, and is easily dissolved by weak nitric acid. Its compounds have a limited use in medicine and the arts.