| 3739·30 | 4319·12 | 4424·55 | 4519·80 |
| 4152·38 | 4329·21 | 4434·07 | 4524·08 |
| 4203·18 | 4334·32 | 4434·52 | 4544·12 |
| 4225·48 | 4347·95 | 4452·92 | 4566·38 |
| 4229·83 | 4391·03 | 4454·84 | 4577·88 |
| 4236·88 | 4420·72 | 4458·70 | 4642·41 |
| 4256·54 | 4421·32 | 4467·50 | 4674·79 |
[299] Exner and Haschek; Eder and Valenta; Rütten and Mersch, Zeitsch. wiss. Photochem. 1905, 3, 181.
CHAPTER XIII
THE TERBIUM GROUP
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, Yα and Yβ from the same mineral; Yβ was afterwards found to be identical with samaria, whilst Yα 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.