THE DETECTION AND WIDE DISTRIBUTION OF YTTRIUM. 
895 
The citron band not due to calcium. 
11. Evidence stronger than this in favour of the view that the citron band was an 
inherent characteristic of calcium could scarcely be ; but, on the other hand, there was 
evidence equally conclusive that the band was not essential to calcium. The ammonia 
precipitate (5) sometimes gave the citron band with great strength and purity, and 
although I had not yet obtained this in quantities sufficient for a detailed examination, 
it was easy to decide that it contained no phosphoric, silicic, or boric acid, fluorine, or 
other body likely to cause the precipitation of lime in this group. This precipitate 
must therefore be an earth, and the more carefully I purified it from lime and other 
substances, the more brilliantly shone out the citron band, and the more intense 
became the green and red bands. 
Another stubborn fact was this :—Starting with a lime compound which showed 
the citron band, I could always obtain a calcic oxalate which gave the band stronger 
than the original substance ; but if I started with a lime compound which originally 
gave no citron band, I could never by any means, chemical or physical, constrain the 
lime or the earthy precipitate to yield a citron band. 
12. Among the minerals tried was eudialyte, a silicate of zirconium, iron, calcium, 
and sodium, containing about 10 per cent, of lime. No citron band could be detected 
on testing the original mineral or any of the constituents separated from it on analysis. 
This, and a lump of common whiting (levigated chalk), were for some time my only 
sources of lime which gave no citron band. 
13. The only explanation that I could see for this anomaly was that the elusive 
citron band was caused by some element precipitated with the calcic oxalate, but 
present in a quantity too small to be detected by ordinary chemical means. I then 
thought that were I to fractionally precipitate the solution of lime, the band-forming 
body might be concentrated in one or the other portion. Accordingly the calcic 
oxalate (7, 8, 9) was ignited and dissolved in hydrochloric acid, and fractionally 
precipitated in three portions with amnionic oxalate, the first and third portions 
being comparatively small. They were dried, ignited with sulphuric acid, and tested 
in the radiant matter tube. All three portions showed the citron band, but the 
portion which came down first gave the band decidedly the strongest, and the third 
portion precipitated showed it weakest. This therefore pointed to a difference between 
calcium and the body sought for. The process, however, was not satisfactory, and I 
was driven to seek some other method. 
14. A portion of an ammonia precipitate found to give the citron band very well 
(5, 11) , was dissolved in dilute sulphuric acid, and the solution evaporated down. 
Crystals were formed which were difficultly soluble in hot water, but appeared more 
soluble than calcic sulphate. 
A large quantity of the calcic oxalate (7, 8, 9) was ignited with sulphuric acid at a 
dull red heat, and the resulting calcic sulphate was finely ground and then boiled in a 
5 Y 2 
