Detection.

—The absorption spectra of neodymium compounds have been examined by Demarçay, Forsling, von Welsbach, Rech, Schäfers, and Baxter and Chapin, with concordant results. The positions of the absorption maxima as given by Holmberg[288] from the measurements of Forsling are as follows, the weaker bands being omitted:

677·5 532·3 -In concentrated solution these give one intense band.468·7
621·7521·6461·0
578·5 -In concentrated solution these give the intense absorption region in the yellow.520·4427·1
575·4512·4
573·5508·7
571·6474·5

The arc spectrum is given by Exner and Haschek, Bertram,[289] and Eder and Valenta.[290] The most intense lines are as follows:

3863·524375·115923·35
3951·324385·815319·98
4061·274400·965594·58
4156·304446·515620·75
4247·544451·716310·69
4282·674463·096314·69
4303·784920·846385·32
4325·87

[288] Zeitsch. anorg. Chem. 1907, 53, 83.

[289] Zeitsch. wiss. Photochem. 1906, 3, 16.

[290] Sitzungsber. kaiserl. Akad. Wiss. Wien, 1910, 119, IIa, 554.

Samarium, Sa = 150·4

The samarium of the earlier chemists (see [p. 168]) contained a large proportion of the terbium elements, from which a fairly complete separation was first effected by Demarçay in 1900.[291] By the fractional crystallisation of the double magnesium nitrate in presence of bismuth magnesium nitrate, Urbain and Lacombe[292] succeeded in preparing samarium compounds, which were shown by spectroscopic examination[293] to be free from other earths. The element is intermediate in electropositive character and in the solubility relations of its salts between neodymium and the terbium earths; its salts are topaz-yellow in colour, and in concentrated solutions show absorption in the blue and violet regions. The oxide is almost white in colour, with only a faint yellow tinge. A systematic investigation of samarium compounds was carried out by Cleve,[294] but his work was vitiated by the fact that his material was very impure. More recently, the pure salts have been examined by Matignon and his pupils.