In his examination of the yttria earths in 1842, Mosander described two new oxides isolated from the old yttria. To one of these, an orange-yellow earth which yielded colourless salts, he gave the name Erbia; the second earth, which was colourless and gave rose-coloured salts, he called Terbia. Bahr and Bunsen examined the yttria oxides in 1866, and obtained only the latter earth, which gave rose-coloured salts; to this they applied Mosander’s name Erbia, and stated that the earth to which Mosander had given that name had no existence. Delafontaine, however, confirmed Mosander’s work, showing that the orange-yellow earth which yielded colourless salts (Mosander’s Erbia) had been fractionated out of their material by Bahr and Bunsen in the double sulphate separation of the cerium group; to avoid further confusion, however, he proposed to give to this oxide (Mosander’s Erbia) the name Terbia, leaving for the colourless oxide, which forms rose-coloured salts (which Mosander had called Terbia) the name Erbia applied to it by Bahr and Bunsen. This reversed nomenclature has been generally accepted. Delafontaine,[300] continuing his work on the earths from samarskite (see p. 168) announced in 1878 the discovery of a new oxide, Philippia, intermediate between terbia and yttria; but this was subsequently shown to be a mixture of yttria and terbia (see p. 133). In the same year, Lawrence Smith[301] announced the discovery of another oxide, Mosandria, from the samarskite earths; this was afterwards shown by Lecoq de Boisbaudran to be a mixture of terbia with gadolinia.[302] In 1880 Marignac[303] announced the discovery of two more new oxides, Y_{α} and Y_{β} from the same mineral; Y_{β} was afterwards found to be identical with samaria, whilst Y_{α} was subsequently separated from the old terbia earths by Lecoq de Boisbaudran, who proposed, with the assent of Marignac, the name Gadolinium.[304] The terbia left after removal of the erbia earths and gadolinia was believed by that author to be still a mixture, a conclusion supported by the work of Hofmann and Kruss in 1893.[305] [300] _Compt. rend._ 1878, ~87~, 559. [301] _Ibid._ 1878, ~87~, 146. [302] _Ibid._ 1886, ~102~, 647. [303] _Compt. rend._ 1880, ~90~, 899. [304] _Loc. cit._ [305] _Zeitsch. anorg. Chem._ 1893, ~4~, 27. In 1886 Demarçay[306] isolated from samaria a new oxide, which he designated S₁. From his work on this oxide in 1892-1893, de Boisbaudran[307] concluded that samaria consisted of at least three oxides, samaria proper, and two new oxides Z_{ξ} and Z_{ε}. In 1896, Demarçay[308] separated an earth Σ, which showed the spark-spectrum of Z_{ε} and the reversal spectrum of Z_{ξ}, and finally in 1901[309] he obtained the new oxide in a fairly pure condition, and gave it the name Europia. [306] _Compt. rend._ 1886, ~102~, 1551. [307] _Ibid._ 1892, ~114~, 575; _ibid._ 1893, ~116~, 611 and 674. [308] _Ibid._ 1896, ~122~, 728. [309] _Ibid._ 1901, ~132~, 1484.