915 
THE DETECTION AND WIDE DISTRIBUTION OF YTTRIUM. 
bluish-green band; at 4110 to 4125 in a blue band; and at 4296 another blue band 
commences, and, extending a short distance, fades away so gradually as to render 
measurement of the further side impossible. At 5052 and 5351 are two violet lines, 
but they are not sufficiently sharp to enable accurate measurements to be taken. 
I have carefully compared the spark spectrum given by yttric chloride with the 
phosphorescent spectrum, and have not found any similarity between them, neither 
have I detected any discontinuity of spectrum on examining the faint light shown 
by yttrium compounds in Becquerel’s phosphorescope. 
73. The above description applies to the spectrum shown either by pure yttria or by 
an earth tolerably rich in yttria. When traces are present the citron band only is 
seen. A little more yttria brings out the first and then the second green band, and 
finally, as the proportion of yttria increases, the red and blue bands appear (80 to 86). 
Circumstances modifying the yttria spectrum. 
74. In the early days of this investigation I frequently found that an earthy 
mixture which by one mode of treatment gave no spectrum, would give a good citron 
band by a modification of the treatment, and I gradually found that I was most likely 
to get the spectrum when the body had been treated with sulphuric acid and then 
ignited to dull redness (4). Not knowing the circumstances governing the appearance 
of the citron band, it would not then have been safe to have altered this mode of treat¬ 
ment. Now, however, having ascertained the earth to which the spectrum was due, 
and having a considerable quantity at my disposal, experiments were tried on other 
methods of treating yttria before exposing it in the radiant matter tube. 
75. Pure yttria precipitated by ammonia from the sulphate was dried at a tempe¬ 
rature below redness and tested. It did not phosphoresce in the slightest degree, 
and, necessarily, no citron-band spectrum was to be seen. The yttria was removed 
from the tube, converted into sulphate, heated to redness, and again tested. It now 
gave the citron band magnificently. This shows what apparently trivial circumstances 
will alter the whole course of an investigation. In 1881, when searching for discon¬ 
tinuous phosphorescent spectra, I tried a similar experiment with pure precipitated 
yttria (45), and entirely missed its citron-band spectrum. Had I first treated the 
yttria with sulphuric acid, instead of testing the earth itself in the radiant matter 
tube, the results would have been very different, and this research would probably 
have never been undertaken. 
76. Yttria was now prepared by igniting the precipitated oxalate at a red heat. 
On testing in the radiant matter tube it phosphoresced with feeble intensity, the 
light being about one-twentieth of that given by the ignited sulphate under similar 
conditions. The citron band was almost as sharp as the sodium line, and was shifted 
one division towards the blue end, now occupying the position 3050 to 3060, its 
