﻿Chemistry cmd Physics. 403 



tainty and only beginning to see my way towards arranging into 

 a consistent whole the facts daily coming to light, help came 

 from an unexpected quarter. M. de Marignac kindly sent me a 

 small specimen of the earth which he had discovered and provis- 

 ionally named Ya (now gadolinia). In the radiant matter tube 

 this earth gave a spectrum like that of yttria with the chief char- 

 acteristic band — the citron band — left out, and with the double 

 green band of samaria added to it. A mixture of 61 parts of 

 yttria and 39 parts of samaria gives a spectrum identical almost 

 to the minutest detail with the spectrum of Ya, except that the 

 citron band is as prominent in it as any other line. Ya consists 

 therefore of samaria with the greenish-blue of yttria and some of 

 the other bands of yttria added to it." "I may aptly call the Ya 

 spectrum," he continues, " my Rosetta stone. It threw a flood of 

 light on all the obscurities and contradictions I had found so 

 plentiful and showed me that a much wider law than the one I 

 had been working upon was the true law governing the occur- 

 rence of these obscure phenomena. For what does the spectrum of 

 Ya show ? It proves that what I had hitherto thought was one 

 of the chief bands in the yttria spectrum — the citron band — could 

 be entirely removed, whilst another characteristic group — the 

 double green of yttria — could also be separated from the citron." 

 The amount of labor involved in these fractionings was very 

 great, a single point often requiring more than 2,000 fractiona- 

 tions to settle it. "Excessive and systematic fractionation has 

 acted the part of a chemical ' sorting demon,' distributing the 

 atoms of yttrium into several groups* with certainly different 

 phosphorescent spectra and presumably different atomic weights, 

 though all these groups behave alike from the usual chemical 

 point of view. Here then is one of the elements, the spectrum of 

 which does not emanate equally from all its atoms but some atoms 

 furnish some, other atoms others, of the lines and bands of the 

 compound spectrum of the element." To test the question 

 whether nature has ever effected such a separation, Mr. Crookes 

 subjected pure yttria (pure in respect to every other known ele- 

 ment) from different minerals, to the radiant matter test. Sarnars- 

 kite yttria gave all the constituent atom-bands, deep red, red, 

 orange, citron, greenish-blue and blue in fair proportion, the first 

 being faintest. Gadolinite yttrium gave the citron and greenish- 

 blue constituents plentiful, the red very deficient, the orange ab- 

 sent, the others moderate. Xenotime yttria gave the citron the 

 most abundant, the greenish-blue smaller, the red all but absent, 

 and the orange absent. Monazite yttria gave the greenish-blue 

 and the citron, the other constituents being in fair proportion and 

 the red good. Fluocerite yttria is quite similar, though the blue 

 is weaker. Hielmite yttria is very rich in citron, has a fair quan- 

 tity of blue and greenish-blue, less of red, no orange and only a 



* In a communication to the Section on the fractionation of yttria, Mr. Crookes 

 stated that there are certainly five and probably eight, constituents into which 

 yttrium may be split. 



