[350] Ibid. 1879, 89, 521.
[351] Ibid. 1879, 89, 478, 708.
Lecoq de Boisbaudran[352] in 1886 showed Cleve’s Holmia to be a mixture of at least two oxides; he retained the name Holmium for the element which gave the most characteristic absorption bands of the old holmium, and proposed the name Dysprosium (from δυσπροσιτος, difficult of access) for the second element. The name Erbia was retained for the oxide remaining after the removal of holmia, thulia, and dysprosia from the old erbia; the homogeneity of this erbia has been called in question, but is now fairly firmly established. The individuality of dysprosium[353] and holmium[354] may also be regarded as definitely established; that of thulium remains doubtful (see [p. 204]).
[352] Ibid. 1886, 102, 1003, 1005.
[353] Urbain, Compt. rend. 1906, 142, 785.
[354] Holmberg, Zeitsch. anorg. Chem. 1911, 71, 226.
The homogeneity of ytterbia was questioned by Auer von Welsbach[355] in 1906; by fractionation of the ammonium double oxalates, that author isolated the oxides of two new elements, for which he proposed the names Aldebaranium and Cassiopeium. By fractionation of the nitrates from nitric acid solution, Urbain[356] arrived at the same result, and proposed the names Ytterbium (Neoytterbium) and Lutecium, which have been adopted by the International Committee. The latter author, employing the same method in the fractionation of the gadolinite earths, has recently obtained very strong evidence of the existence in this group of another element, for which he proposes the name Celtium;[357] the discovery, however, awaits confirmation.
[355] Monats. 1906, 27, 935; 1908, 29, 121.
[356] Compt. rend. 1907, 145, 759.
[357] Ibid. 1911, 152, 141.