506 



Mr. W. Crookes. 



[June 10, 



sions I now bring before this Society. More than 2000 fractionations 

 have been performed to settle this single point. I will content myself 

 with stating the results. The element hitherto called yttrium appears 

 to be a highly complex molecule, capable of being dissociated into 

 several simpler substances, each of which gives a phosphorescent spec- 

 trum of great simplicity, consisting for the most part of only one line. 



Taking the constituents in order of approximate basicity (the 

 chemical analogue of refrangibility) the lowest earthy constituent 

 gives a violet band (X 456), which I have reason to believe belongs 

 to ytterbia. Next comes a deep blue band (X 482) ; then the strong 

 citron band (X 574), which has increased in sharpness till it deserves 

 to be called a line ; then come a close pair of greenish-blue lines 

 (X 549 and X 541, mean 545) ; then a red band (A, 619), then a deep 

 red band (X 647), next a yellow band (X 597), then another green 

 line (X 564) ; this (in samarskite yttria) is followed by the orange 

 line (X 609) of which I have already spoken ; and finally, the three 

 samarium bands remain at the highest part of the series. These for 

 the present I do not touch, having my hands fully occupied with the 

 more easily resolvable earths. 



In the " Comptes rendus " for April 19th, 1886, M. de Boisbaudran 

 announces to the Academy that M. de Marignac, the discoverer of Ya, 

 had selected for it the name Gadolinium. In February last I gave a 

 short note on the earth Y«* in which I described its phosphorescent 

 spectrum (agreeing exactly with that given by Yxoi M. de Marignac' s 

 preparation). Referring to my paper it will be seen that Ya. is com- 

 posed of the following band-forming bodies: — (541, 549), (564), 

 (597), (609), (619), together with a little samarium. Calling the 

 samarium an impurity, it is thus seen that gadolinium is composed of 

 at least four simpler bodies. The pair of green lines (X 541 and 

 X 549, mean 545), being the strongest feature in its spectrum, may 

 be . taken as characteristic of gadolinium : the other lines are due to 

 other bodies. 



It is by a method of his own, differing from mine, that M. de Bois- 

 baudran has obtained phosphorescent spectra of some of these earths. 

 He takes the induction spark between the surface of a strong and 

 acid solution of the metallic chloride, and a clean platinum wire a few 

 millimetres above it. The platinum wire is kept negative and the 

 solution positive ; it is then observed that in many cases a thin layer 

 of fluorescent light is seen at the surface of the liquid. This layer 

 gives a spectrum of nebulous bands. For the sake of brevity I will 

 adopt M. de Boisbaudran's term, and call this process the method of 

 reversion (the direction of the spark being reversed). As this method 

 is entirely different to the one I adopt, it is not surprising that the 

 results also are different. Experimenting in this way M. de Bois- 

 * "Proc. Eoy. Soc," vol. 40 (1886), p. 236. 



