260 Scientific Proceedings, Royal Dublin Society. 
PREPARATION OF PurE YrTrrRia. 
The preliminary experiments showed that, on fusing the mixed 
nitrates of lanthanum, didymium, and yttrium, and _ then 
dissolving in water, the whole of the yttria is contained in the 
insoluble or basic nitrates, the solutions being spectroscopically 
free from yttrium. There is also a marked concentration of 
didymium in the insoluble portion, as this portion gives much the 
most intense absorption-bands. ‘The separation of the yttria can 
be readily followed by the presence or absence of the line 
A 2817-1, just beyond gold line No. 20. 
The whole of the oxides from which the ceria had been 
removed were dissolved in nitric acid, and evaporated down, then 
fused in a platinum basin until the oxides of nitrogen came off 
pretty freely, and the melt became stiff; but the temperature was 
never allowed to reach a red heat; on cooling, water was added, 
and the whole boiled up, and the insoluble basic nitrates filtered 
off. ‘The filtrate was again boiled down, fused, and similarly 
treated, yielding two fractions. The solid or decomposed frac- 
tion, from the first treatment, was redissolved in nitric acid, 
evaporated to dryness, and fused with four times its weight of 
potassium nitrate, the latter being added to keep the mass in a 
fused state, facilitating the decomposition of the nitrates of 
yttrium and didymium, and retarding the decomposition of the 
lanthanum nitrate. On boiling the melt with water, and filtering 
off the basic nitrates, which amounted roughly to about one 
quarter of the whole quantity treated, they were found to contain 
all the yttrium; and this product was much richer in didymium 
than any of the other three fractions, as, with solutions of equal 
concentration, it gave much the most intense absorption-bands ; 
but it still contained large quantities of lanthanum, and gave a 
strong spark-spectrum of that element, as well as the lines of the 
other two. 
To remove the didymium and the remainder of the ianthanum, 
this fourth fraction was dissolved and treated with excess of 
potassium sulphate, a bag of crystals being hung in the beaker; 
after standing two or three days, the crystalline pink precipitate 
was filtered off, and found to be free from yttrium ; but the solution 
still showed absorption-bands, so the bases were precipitated by 
