Shiny gray metal which readily oxidizes to form a green oxide. m.p. 799 ºC; 1470 ºF b.p. 3426 ºC; 6199 ºF density 6.657 g/cc (25 ºC); 415.583 pound/cubic foot (77 ºF)	memory peg
	1803 Wilhelm Hisinger & Jöns Jakob Berzelius, Sweden / Martin H. Klaproth, Germany
	Ceres, asteroid discovered in 1801 and named after the Roman goddess of agriculture

The rare earths are so very much alike and occur closely associated in such complex minerals that it was extremely difficult to separate them. They were all obtained, however, by elaborate and laborious fractionation of two mixtures, the "yttria" of Gadolin and the "ceria" of Klaproth, Berzelius, and Hisinger, originally believed by their discoverers to be pure oxides. (M.E. Weeks 1968, p. 667).

Elements discovered in ceria
(Click on the yellow circles for the element pages).
(Click here for the yttria group).

The story of ceria and all new earth within started with the report on the the "heavy stone of Bastnäs" by the mineralogist Axel Fredrik Cronstedt of 1751. Vilhelm Hisinger (1766-1852) belonging to the family owning the Bastnäs mine, sent at the age of 15 samples of this tungsten (Swedish for "heavy stone") from this mine to Carl Scheele who found nothing new. In 1803 Vilhelm Hisinger, now ironmaster, together with Jöns Jakob Berzelius (1779-1848) reinvestigated cerite, as the "heavy stone of Bastnäs" later was named, expecting to find yttria, the new earth which was six years before discovered by Johan Gadolin in a dense black mineral (cf. Yttrium).

They isolated an earth similar to yttria but recognized it was distinct. They gave the new earth the name ceria in honour of Ceres, the first asteroid, discovered two years previous, in 1801, by Giuseppi Piazza. Ceres was in Roman mythology the goddess of agriculture.

Their report was sent to Adolph Ferdinand Gehlen (1775-1815) in Germany to be published in his Neues Allgemeines Journal der Chemie. In order to establish priority, it was also printed in Swedish as a small pamphlet issued in only 50 copies, which are now of extreme rarity.

Indepently, Martin Heinrich Klaproth (1743-1817) analyzed tungsten from Bastnäs, he called the new earth ochroite. Klaproth presented also his results in Gehlen’s Journal, where his article appeared in an issue just before that containing the report of Hisinger and Berzelius.

It is not known at which exact time Gehlen received each paper for publication, but in his letter to Hisinger in May 1804 Gehlen gives Berzelius and Hisinger the honor of having discovered a new metal and as a consequence, their suggested name has prevailed. Klaproth suggested the more correct name Cererium, but this name was not accepted. Nowadays it is generally accepted that the discovery took place simultaneously and independently. Hisinger, Berzelius and Klaproth are usually named as co-discovers of Cerium.

Thirty-six years later, in 1839, Mosander showed that the Cerium oxide isolated by these researchers was composed of at least two oxides, for one of which he retained the name ceria and the second he called lanthana, which subsequently in 1842 was shown to consist of lanthana and the new earth didymia. Mosander announced the results of his research in a paper held in July 1842 in Stockholm. An English translaten was published in the Philosophical Magazine, and after this a German version in Poggendorf's Annalen: "Ueber die das Cerium begleitenden neuen Metalle Lanthanium und Didymium, so wie über die mit der Yttererde vorkommenden neuen Metalle Erbium und Terbium" (On the new metals Lanthanum and Didymium, accompanying Cerium, and on the metals Erbium and Terbium occuring with yttria) (note) (see scheme above, and further Lanthanum).

In Greek the name Δημητριο [dimitrio] is used after Δημητερ [Demeter], the Greek equivalent of Ceres.

See also: Chronological list of discovery of the rare earths, their names in different languages etc. on the Yttrium page

• Mary Elvira Weeks, Discovery of the Elements, comp. rev. by Heny M. Leicester (Easton, Pa.: Journal of Chemical Education, 1968), pp. 525-532 & 667-699.
• Seltene Erden. Gmelins Handbuch der anorganische Chemie, 8. Aufl.; System-Nummer 39 (1938).
• Lauri Niinistö, "Discovery and Separation of Rare Earths". In Rare Earths, ed. Regino Sáez Puche & Paul A. Caro, 25-42. Madrid: Editorial Complutense, 1997.
• Lauri Niinistö, "Swedish Contributions to the Discovery of Elements: Part 2: The Work of Berzelius." ERES Newsletter, vol. 10, no. 1 (31 August 1999). (on-line).