THE DETECTION AND WIDE DISTRIBUTION OF YTTRIUM. 
913 
spectrum, evidently due to impurity. On repeating the operation several times I at 
last succeeded in obtaining a white earth which gave only the merest trace of citron- 
band spectrum. Its hydrogen equivalent, 58’0, and its chemical properties showed 
that it was probably Marignac’s ytterbia. Subsequent experiments satisfied me that 
this earth did not contain more than 1-10,000th part of yttria (84, 87). The extreme 
tediousness of the chemical operations necessary to obtain this high degree of purity, 
and the long time they require, prevented me from pushing these results beyond what 
was necessary to prove the special point at issue. 
Purification of yttria. 
69. The white earth obtained in the operation described at par. 65 might still 
contain traces of terbia, together with erbia, holmia, and thulia. I had relied on the 
absence of absorption spectrum as proving the absence of erbia, holmia, and thulia, 
but this test is not a very delicate one, and a final purification was therefore attempted. 
The decomposition of the fused nitrates was now the process relied on for this final 
purification, the yttric nitrate resisting nearly a red heat without decomposition, whilst 
the erbic, holmic, and thulic nitrates are decomposed at a much lower temperature. 
The operation was carried on as described at par 60. 
The yttric nitrate left undecomposed, after repeated fusions, was now fused at a 
higher temperature, extracted with water, filtered from insoluble residue, and the 
operation repeated on the filtrate. After several such operations the H equivalent 
of the yttria was taken at every succeeding operation, and the spectral appearance in 
the radiant matter tube was also examined. The equivalent gradually got down 
to 31’0, but the spectra did not vary very much; that from the earth of lowest 
equivalent being, however, the most brilliant. 
70. The yttric nitrate, prepared from gadolinite and freed from ytterbia by the 
fusion of the nitrates (68), was converted into oxalate and ignited. The resulting 
yttria was quite white, and on testing in the radiant matter tube gave a spectrum 
absolutely identical with that given by the zircon (18), cerite (25), thorite and 
orangite (33, 34), and samarskite (64, 69), yttrias. Pure yttria was also prepared 
from yttro-tantalite, euxenite, allanite, tyrite, and also from plaster of Paris (15) 
and common limestone. In no case could I detect any difference in the position or 
intensity of the lines shown by their phosphorescent spectra. 
The phosphorescent spectrum of yttria. 
71. The spectrum shown by pure ignited yttric sulphate in a radiant matter tube 
is one of the most beautiful objects in the whole range of spectroscopy. The lines are 
not so sharp as those given by spark spectra, but are more like the flame spectra 
