[314] Urbain and Bourion, Compt. rend. 1911, 153, 1155.
[315] J. Amer. Chem. Soc. 1913, 35, 754.
Atomic Weight.
—Using the material isolated from samaria, Demarçay[316] in 1900, by the synthetic sulphate method, found the atomic weight of europium to be about 151. Urbain and Lacombe[317] determined the value in 1904, with material free from gadolinium and samarium, using the three ratios which they employed in the case of the latter element (see [p. 182]); their values, corrected by Brauner, were 152·00, 151·93 and 151·94 respectively. Another series of determinations was carried out by Jantsch[318] in 1908, the same method being employed; he obtained the mean value 152·03, with an error of ±·02. The International Committee have adopted the value 152·0.
[316] Compt. rend. 1900, 130, 1469.
[317] Ibid. 1904, 138, 627.
[318] Ibid. 1908, 146, 473.
Detection.
—The absorption spectrum was determined by Demarçay,[319] but is not sufficiently intense or characteristic for ordinary purposes of detection. The spark spectrum has been investigated by the same author (loc. cit.); it is very bright, and shows the three blue rays which characterised Lecoq de Boisbaudran’s Zε. The reversal spectrum shows the characteristic band of Zξ.
The pure oxide, according to Urbain,[320] shows no luminescence under the influence of cathode rays, but when impure, or very largely diluted with lime or gypsum, it gives very bright and characteristic spectra.