118 



INORGANIC EVOLUTION. 



[CHAP. 



to be elementary) would be impurities in didymium. They constitute 

 a veritable splitting up of the yttrium molecule into its constituents." 



FIG. 37. Showing how by the method of fractional oil yttria is separated into fire 

 different substances, defined spectroscopically by the different intensities of 

 the phosphorescent lines. 



" The final result to which I have come is that there are certainly 

 five, and probably eight, constituents into which yttrium may be split. 

 Taking the constituents in order of approximate basicity (the chemical 

 analogue of refrangibility) the lowest earthy constituent gives a deep 

 blue band Ga (X 482) ; then there is the strong citron band GS (A. 574), 

 which has increased in sharpness till it deserves to be called a line ; 

 then come a close pair of greenish-blue lines, G/3 (A 549 and A 541, 

 mean X 545); then a red band, Gf (A 619), then a deep red band, 

 Grj (y 647); next a yellow band, Gt (A 597); then another green band, 

 Gy (A 564) ; this (in samarskite and cerite yttria) is followed by the 

 orange line So (A 609). The samarium bands remain at the highest 

 part of the series. These, I am satisfied, are also separable, although 

 for the present I have scarcely touched them, having my hands fully 

 occupied with the more easily resolvable earths. The yellow band, 

 Ge, and green band, Gy, may in fact be due to a splitting up of 

 samarium." 



So far as I know, Sir William Crookes has not" yet named the 



