The lanthanides

Abstract

In 1794, J. Gadolin obtained yttria, impure yttrium oxide, from the mineral now known as gadolinite, while in 1803, Berzelius and Klaproth isolated the first cerium compound. Subsequent research over the ensuing century demonstrated, first, that yttria was a mixture of the oxides of yttrium, erbium and terbium; and that cerite was made up of the oxides of lanthanum and cerium (Mosander, 1839–43); secondly that the original ‘erbium oxide’ in fact contained erbium, holmium, thulium and ytterbium (Cleve, Marignac, 1878–80). Similarly, Mosander’s separation of ‘didymium’ from lanthanum was later eclipsed by its separation into samarium, europium, neodymium and praseodymium.