1905.] On Europium and its Ultra-violet Spectrum. 551 



MM. Urbain and Lacombe* have sharply separated europium from 

 samarium in the manner outlined by them in my note on gadolinium f 

 by fractional crystallisation of the double nitrates of bismuth or 

 magnesium with the nitrates of the rare earths. I owe to the 

 kindness of M. Urbain a sufficient quantity of the oxide of europium 

 to enable me to obtain a good series of its photographed spectrum, a 

 copy of which accompanies the present paper, (Not reproduced.) 



Exner and Haschek have measured the wave-lengths of the europium 

 lines | from material supplied by Dema^ay. A comparison of their 

 tines with mine shows that the material was by no means pure. 



Urbain's europia is not quite so free from impurities as his gadolinia. 

 I have been able to detect in my photographs the following lines : 

 Gadolinium is represented by very faint lines at 3450-55, 3481-99, 

 3585-10, 3646-36, 3654*79, 365'32, 3664-76, 3697-90, 3699*89, 3743*62, 

 3768-52, 3796-58, 3805-70, 3850-83, 3851-16, 4050-08, 4225-33. 

 Yttrium is represented by the line at 3774*51, lanthanum by the line 

 at 3988-66, and calcium by the two lines at 3933-825 and 3968-625. 



No lines of bismuth or magnesium are to be seen. 



Most of the lines of impurities are exceedingly faint, showing that 

 the impurity is only present in very minute proportion. Indeed, I 

 have only mentioned them if they correspond with strong lines in the 

 gadolinium or other spectra. Both in the europium and the gadolinium 

 spectrum I have not attempted to give wave-lengths of all the excessively 

 faint lines. If at some future time it becomes of interest or value to 

 .ascertain their wave-lengths, all the necessary data are present whereby 

 they can be identified. 



* 'Comptes Kendus,' vol. 138, pp. 84, 627, 1166; 'Chemical News,* vol. 89, 

 pp. 52, 179, 277. 



f Supra, p. 420. 



J ' Wellenlangen-Tabellen f 'iir Spektralanaly tische Untersuchungen/ F. Deutioke, 

 .Leipzig und Wien, 1902. 



2 S 2 



