DIDYMIUM (from the Gr. &Segos, twin)
This article appears in Volume V08, Page 208 of the Encyclopedia Britannica.
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DIDYMIUM (from the Gr. &Segos, twin) , the name given. to the supposed element isolated by C. G. Mosander from cerite (1839-1841). In 1879, however, Lecoq de Boisbaudran showed that Mosander's "didymium " contained samarium; while the residual " didymium ," after removal of samarium, was split by Auer v. Welsbach (Monats. f. Chem'ie, 1885, 6, 477) into two components (known respectively as neodymium and praseodymium) by repeated fractional crystallization of the double nitrate of ammonium and didymium in nitric acid. Neodymium (Nd) forms the chief portion of the old " didymium. " Its salts are reddish violet in colour, and give a characteristic absorption spectrum. It forms oxides of composition Nd203 and Nd205, the latter being obtained by ignition of the nitrate (B. Brauner). The atomic weight of neodymium is 143.6 (B. Brauner, Proc. Chem. Soc., 1897-1898, p. 70). Praseodymium (Pr) forms oxides of composition Pr203, Pr206,xH2O (B. Brauner), and Pr407. The peroxide, Pr407, forms a dark brown powder, and is obtained by ignition of the oxalate or nitrate. The sesquioxide, Pr203, is obtained as a greenish white See Also: - WHITE
- WHITE, ANDREW DICKSON (1832– )
- WHITE,
GILBERT See Also: - GILBERT
- GILBERT (KINGSMILL) ISLANDS
- GILBERT (or GYLBERDE), WILLIAM (1544-1603)
- GILBERT, ALFRED (1854– )
- GILBERT, ANN (1821-1904)
- GILBERT, GROVE KARL (1843– )
- GILBERT, J
- GILBERT, JOHN (1810-1889)
- GILBERT, MARIE DOLORES ELIZA ROSANNA [" LOLA MONTEZ "] (1818-1861)
- GILBERT, NICOLAS JOSEPH LAURENT (1751–1780)
- GILBERT, SIR HUMPHREY (c. 1539-1583)
- GILBERT, SIR JOSEPH HENRY (1817-1901)
- GILBERT, SIR WILLIAM SCHWENK (1836– )
(1720–1793) - WHITE, HENRY KIRKE (1785-1806)
- WHITE, HUGH LAWSON (1773-1840)
- WHITE, JOSEPH BLANCO (1775-1841)
- WHITE,
RICHARD GRANT (1822-1885) - WHITE, ROBERT (1645-1704)
- WHITE, SIR GEORGE STUART (1835– )
- WHITE, SIR THOMAS (1492-1567)
- WHITE, SIR WILLIAM ARTHUR (1824--1891)
- WHITE, SIR WILLIAM HENRY (1845– )
- WHITE, THOMAS (1628-1698)
- WHITE, THOMAS (c. 1550-1624)
mass by the reduction of the peroxide. The salts of praseodymium are green in colour, and give a characteristic spark spectrum. The atomic weight of praseodymium is 140'5.
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