Читать книгу The Rare Earths: Their Occurrence, Chemistry, and Technology - Stanley Isaac Levy - Страница 163

[45]—A silicate of yttria earths, chiefly scandia, of the formula R₂O₃,2SiO₂. Scandia forms about 37 per cent. of the whole (R. J. Meyer); yttria with small quantities of the other yttria earths forms the bulk of the remainder of the bases, the ceria group being almost completely absent. Ferric oxide (with traces of manganic oxide and alumina) forms about 3 per cent. Thorium is present only in traces, and radioactivity is barely perceptible.

[45] J. Schetelig, Centr. Min. 1911, 721.

Thortveitite is the first mineral to be discovered in which the content of scandia is greater than 2 per cent.; in 1908 Crookes[46] examined a very large number of yttria minerals for scandia, and finally chose for extraction of the earth Wiikite (q.v.) which has a scandia content of 1·2 per cent.[47]

[46] Phil. Trans. 1908, A, 209, 15.

[47] According to Eberhard, some varieties of Wiikite have a much lower scandia content.