1887.] 



On Radiant Matter Spectroscopy. 



129 



sharp orange line is not strong enough to be seen in the phosphoro- 

 scope. A little calcium entirely suppresses the orange line, while 

 samarium or yttrium seems to intensify it. 



In addition to the above earths, it is not improbable that the sharp 

 green line (l/\ 3 325) mentioned under the heading "Yttrium" 

 may be caused by still another earth. 



The brilliant and characteristic spark spectra yielded when certain 

 elements are volatilised and rendered incandescent by the spark from 

 a powerful induction coil are relied on by chemists as an indisputable 

 proof of the identity of such elements. Bearing this in mind I have 

 endeavoured to ascertain how these yttrium constituents would behave 

 in respect to the spark spectrum. Do the definite system of lines in 

 the old yttrinm spark spectrum belong to one constituent only, or are 

 the yttrium lines broken up and distributed among the different 

 bodies I have designated as Gx, Gr/3, &c. ? Also do the other con- 

 stituents possess special spark spectra of their own ? Very caref ul 

 and long-continued experiments have shown me that neither of these 

 hypothetical cases occur. 



The spark spectrum given by old yttrium is shown in the drawing 

 (fig. 5), It is chiefly characterised by two very strong groups of 

 lines in the red and orange. I now take the earth Ge>. This occurs 



Fig. 5. 



near one end of the fractioning, and not only differs from the parent 

 yttrium in its phosphorescent spectrum, but by virtue of the process 

 adopted for its isolation it must likewise differ in its chemical pro- 

 perties. On examining its spark spectrum I see absolutely no 

 difference between this spectrum and the one given by old yttrium. 



I now pass to the other end of the fractionation of yttrium, where 

 occurs a concentration of a body giving a totally different phospho- 

 rescent spectrum to the one at the first end. And it also differs 

 chemically from old yttrium, and in a more marked manner from its 

 brother, G3, at the other extremity of the fractionation. Here again 

 its spark spectrum is perfectly identical both with old yttrium and 

 with Qc, and however closely I examine these three spectra in my 

 laboratory, the whole system of lines is still identical. 



