9 0G 
ME. W. CROOKES ON RADIANT MATTER SPECTROSCOPY: 
Of these the potassic sulphate reaction (3G) excludes cerium, lanthanum, scandium, 
thorium, yttrium a, and zirconium, so there are left only the following :—- 
Mosandrum, 
Terbium, 
Ytterbium, 
Yttrium. 
44. Certain chemical reactions for a long time made me dismiss yttrium from the 
list of likely bodies. In my analysis of zircons (18), towards the latter part of the 
process, I used the following process to separate the iron :—The solution, mixed with 
tartaric acid and excess of ammonia, was allowed to stand for some time. A small 
quantity of a precipitate gradually formed, which was filtered off, and it was this 
filtrate, after separating the iron with ammonic sulphide, that yielded the greatest 
quantity of substance giving the citron band. Now one of the methods of separating 
yttria from alumina, berylla, thoria, and zirconia is to precipitate it as tartrate in the 
presence of excess of ammonia, the other earths remaining in solution. Fresenius 
says : —“The precipitation ensues only after some time, but it is complete.” 
The precipitate thus obtained with tartaric acid and ammonia should therefore 
contain all the yttria: it gave no citron band whatever in the radiant matter tube; 
whilst the residue, which should be free from yttria (18), proved for a long time the 
only source of material wherewith to investigate the chemical properties of the body 
giving the citron spectrum. 
45. Another reason which made me, at this stage of the research, pass over yttria, 
was that I had already tested this earth in the radiant matter tube. In a paper on 
“ Discontinuous Phosphorescent Spectra in High Vacua,” read before the Royal 
Society, May 19th, 1881,'“ I said—-“Yttria shows a dull greenish light giving a 
continuous spectrum ” (75). 
For these reasons I for a long time omitted yttria from my list of possible bodies, 
and considered that the earth, if not a new one, might turn out to be either mosandra, 
terbia, or ytterbia. 
Analysis of samarshite. 
4G. A very large quantity (about 15lbs. weight altogether) of samarskite was 
worked up, partly by the hydrofluoric acid method of Lawrence Smith,! and 
partly by fusion with potassic bisulpliate. The niobic and tantalic acids after 
purification were found to give no citron band spectrum. 
These methods both gave as a result a large quantity of mixed earths containing 
most, if not all, of the bodies enumerated in par. 40. Tested in the radiant matter 
tube, this material gave the citron spectrum very brilliantly. It was dissolved in 
hydrochloric acid, neutralised as nearly as possible with ammonia, and boiled with 
* Proc. Roy. Soc., No. 213, 1881. 
t ‘ Comptes Eendus,’ vol. 87, p. 146. 
