—Urbain and Demenitroux[365] determined this constant from the ratio Dy₂(SO₄)₃,8H₂O : Dy₂O₃. The mean value of six determinations carried out with material obtained by fractional crystallisation of the nitrate was 162·52; with material purified by the ethylsulphate crystallisation, the mean of six determinations gave the value 162·54. The International Atomic Weight is 162·5.
[365] Compt. rend. 1906, 143, 598.
Detection.
—Lecoq de Boisbaudran[366] and Urbain[367] give the position of the following absorption maxima in the visible and ultraviolet regions respectively:
| ╵ | ||
| 753 | 368·5 | 338 |
| 475 | 379·5 | 332·5 |
| 451·5 | 365 | |
| 427·5 | 351 | |
[366] Ibid. 1886, 102, 1003.
[367] Ibid. 1906, 142, 785.
The arc spectrum of Urbain’s material was examined by Eberhard,[368] who gives as most suitable for detection of the element in a mineral or oxide mixture the following lines:
| 3385·16 | 3898·69 | 4187·00 |
| 3531·86 | 3944·83 | 4211·82 |
| 3536·17 | 4000·59 | |
| 3645·54 | 4078·11 |
See also Exner and Haschek, and Eder and Valenta.[369]