The substances occur, in very minute quantity, in a large number of sparingly-distributed and comparatively rare minerals - euxenite, samarksite, cerite, yttrotantalite, &c. Scandinavian specimens of these minerals were examined by J.
Hisinger and Berzelius, was of ceria, the oxide of cerium, in the mineral cerite found at Ridderhytta, Westmannland, Sweden.
In 1841 Mosander, having in 1839 discovered a new element lanthanum in the mineral cerite, isolated this element and also a hitherto unrecognized substance, didymia, from crude yttria, and two years later he announced the determination of two fresh constituents of the same earth, naming them erbia and terbia.
Mosander from cerite (1839-1841).
It is found in the minerals gadolinite, cerite, samarskite and fergusonite, and is usually obtained from cerite.
For details of the complex process for the separation of the lanthanum salts from cerite, see R.
CERIUM (symbol Ce, atomic weight 140.25), a metallic chemical element which occurs with the rare earths in the minerals cerite, samarskite, euxenite, monazite, parisite and many yttrium minerals.
The crude oxide of the metal is obtained from cerite, by evaporating the mineral with strong sulphuric acid, removing excess of acid and dissolving the residue in ice-cold water; sulphuretted hydrogen is passed through the solution, which is then filtered, acidified with hydrochloric acid, and precipitated as oxalate by oxalic acid; the oxalate is then converted into oxide by ignition.