Terbium

At the 13th meeting of the British Association for the Advancement of Science in Cork, Ireland, from 17-23 August 1843, those present were told of the discovery of four new elements in Sweden. Carl Gustav Mosander, whose remarks are presented here in English translation, had isolated lanthanum in 1839 and didymium in 1840. Freiherr Auer von Welsbach recognised in 1885 that didymium consists of neodymium and praseodymium in the cerite earth (cerite oxide). In 1843, Mosander determined that the ytter earth (yttrium oxide, or yttria in Latin) discovered by John Gadolin in 1794 and described as such by Anders Gustaf Ekeberg in 1797, consists of several oxides: a pink oxide, which he named Terbia; a light yellow oxide, which he called Erbia; and the colourless, for Mosander now pure, Yttria. However, he was only able to isolate the latter impurely.

In 1860, Nils Berlin examined the yttria and isolated Mosander’s terbia. His work also initiated some confusion about the element terbium. In his notes, Berlin wrongly named his find Erbia. This resulted different names for the oxide that Mosander called terbia and Berlin called erbia. Mosander’s information on Terbia seemed to be wrong when compared with that of Berlin’s erbium oxide. It was not until 1906, many errors and confusions later, that the French chemist Georges Urbain confirmed Mosander’s original findings. Urbain succeeded in obtaining pure terbium. Mosander was declared the discoverer of the elements terbium and erbium almost 50 years after his death. The commercial production of pure terbium became possible after the invention of ion exchange technology in the late 1940s.