THE DETECTION AND WIDE DISTRIBUTION OF YTTRIUM. 
893 
under examination with strong sulphuric acid, drive off excess of acid by heat, and 
finally to raise the temperature to dull redness (10). The anhydrous sulphate thus 
left frequently showed the citron band in the radiant matter tube, when before this 
treatment the original substance showed nothing (75). 
Examination of calcium compounds. 
5 . My first idea was that the band might be due to a compound of lime. Much 
chemical evidence tended to support this view. I have already explained that the 
chemical extraction was rendered very difficult by the fact of the citron band so 
frequently turning up both in the precipitate and the filtrate. By neglecting the 
portion showing least citron band, and separating all the elements present which gave 
little or none, I could generally concentrate the citron band into a solution which 
—according to our present knowledge of analytical chemistry—should contain little 
else than the earths, alkaline earths, and alkalies. Ammonia added to this solution 
would precipitate an earth (11, 14), and in the filtrate oxalic acid would precipitate 
an insoluble oxalate (7, 13). 
The citron band hovered between these two precipitates, being sometimes stronger 
in one and sometimes in the other. It was also to be detected, but more faintly, in 
the residue left after evaporating to dryness and igniting the filtrate from the oxalate. 
I frequently obtained no precipitate with ammonia, and then the oxalate gave the 
band brilliantly ; and occasionally the ammonia precipitate when formed gave little or 
no citron band. I was, however, generally sure to find it in the insoluble oxalate, 
and sometimes it was very brilliant, being accompanied by two bright green bands 
and a fainter red band. 
6. At this time one of the minerals which showed the citron band most strongly 
was a phosphorescent apatite from Ireland ; and knowing the difficulties of separating 
the last traces of phosphoric acid from the earths, I explained the foregoing facts by 
the presence of small quantities of phosphoric acid, which gave rise to the ammonia 
precipitate ; the bulk of the citron body not being precipitated by ammonia, but 
coming down as oxalate ; whilst a little of this oxalate would remain dissolved in 
the ammoniacal salts present, and so appear with the alkalies. 
I tested this hypothesis in every imaginable way, by mixing small quantities of 
phosphoric acid with salts of lime and other earths, in the endeavour to imitate the 
conditions occurring in the native minerals, and so educe the citron band ; but I was 
unable to get any precipitate giving the citron band when I started with materials 
which did not originally give it. 
7 . A sufficient quantity of precipitated oxalate (5) having in course of time been 
accumulated, I attempted its purification. It was ignited, dissolved in dilute hydro¬ 
chloric acid, and rendered slightly alkaline with ammonia and amnionic sulphide. 
The liquid was boiled to a small bulk, keeping it alkaline, and was then set aside in 
MDCCCLXXXIII. 5 Y 
