From the Eclipse of Aldebaranium and Cassiopeium to the Priority Conflict Between Celtium and Hafnium

In 1794, Finnish scientist Johan Gadolin discovered the first of the rare earth elements in some ore deposits at Ytterby, Sweden. He called the oxide of the new element that he had isolated ytterbia and ytterbite the ore from which he had extracted it. Three years later, Anders Gustaf Ekeberg verified Gadolin’s discoveries and proposed the name of yttria (or yttric earths) for the oxide and gadolinite for the ore. For many years, chemists, among them L. N. Vauquelin, J. J. Berzelius, and M. H. Klaproth, wrestled with the problem that perhaps Gadolin’s yttrium was not a simple body but in reality contained other elements. In 1842, the Swedish chemist C. G. Mosander described how, by means of the fractional precipitations of the oxalates from dilute solutions of oxalic acid and by treatment of the hydroxides with dilute ammoniacal solutions, he seemed to have succeeded in extracting three new elements. The first was yttrium, the most basic; the second was erbium, the least basic; and the intermediate fraction he called terbium. The names terbium, erbium, and ytterbium derive from the name of the town, Ytterby. The names that Mosander gave to the three elements derived from the sequence in which they were separated: the name yttrium was not changed out of respect for Gadolin. The first element that he extracted, Mosander called terbium, and the following one he called erbium. He removed a letter from the word terbium because he had isolated it later. In the following years, it was discovered that both erbium and terbium were not single elements but mixtures of elements yet unknown. A practice developed that we might call an entente cordiale: when a discoverer split a presumed element into its constituents, one element retained the name already given by its preceding discoverer. This usage was respected by everyone, including Urbain, who, in 1907, presented his discoveries with the names neo-ytterbium and lutecium. Only Auer von Welsbach, a renowned Austrian chemist, did not respect this tacit “gentlemen’s agreement” and called the elements with atomic numbers 70 and 71 aldebaranium and cassiopeium.