tise Fe 
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TRANSACTIONS OF THE SECTIONS. 25 
this communication before a meeting of the Literary and Philosophical Society of 
Manchester a short time ago, soon after he had made the discovery which it contains. 
In the prosecution of the experiments he had received every assistance which the 
works of his friend Mr. Fairbairn could supply; and Mr. Robert Rawson had kindly 
assisted him in the reduction and arrangement of the results of the experiments. 
On the Principles of Construction adapted to the perfection of the Flute. 
By Cornetius Warp. 
The author exhibited a flute of a new construction, intended to combine the ut- 
most theoretical completeness of tone and adaptability to musical ratios, with unusual 
facilities for delicate and varied execution. He presented a memoir in illustration of 
these peculiarities. 

CHEMISTRY. 
On the new metals, Lanthanium and Didymium, which are associated with 
Cerium; and on Erbium and Terbium, new Metals associated with Yitria. 
By Professor C. G. MosanpEer. Communicated by N. L. BEAMIsH, 
F.R.S. 
ALTHoven in consequence of the imperfect nature of the results which were obtained 
from my researches on cerium and lanthanium I had no intention of making any 
communication on the subject on the present occasion, yet after hearing the interest- 
ing statement of Professor Scheerer, it appeared to me that it might be useful to 
make known more generally some particulars which arose during my labours, and 
principally because this advantage may result, that other chemists, after becoming 
acquainted with what 1 am about to state, may possibly be spared the loss of valuable 
time which might otherwise have been fruitlessly expended. 
When, sixteen years since, | made some experiments upon cerium, several circum- 
stances cccurred which led me to the supposition that oxide of cerium was accom- 
panied by some other oxide, which, however, I did not succeed in separating, and 
want of materials prevented me from then prosecuting the inquiry. A few years 
since, having procured a quantity of cerite and cerine, I prepared from thence the 
double salt of sulphate of the oxide of cerium with sulphate of potash, which salt was 
washed with a solution of sulphate of potash, until the passing fluid gave no trace of 
precipitate with caustic ammonia or carbonate of soda. I believed that in this man- 
ner I could obtain a pure salt free from all foreign substances. The double salt was 
afterwards decomposed in the moist way with carbonate of soda, and with the car- 
bonate of protoxide of cerium thus obtained, all the preparations have been made 
which will be now mentioned. 
' After a long examination of various salts of protoxide of cerium, I did not succeed 
in detecting a salt principally consisting of the supposed new oxide, the presence of 
which, however, appeared more and more probable in the course of the experiments. 
As it was known that cerium gives two oxides, I considered it probable that if hydrate 
of protoxide of cerium mixed with water was exposed to the effect of chlorine, per- 
oxide of cerium would be formed while the more electro-positive metallic oxide would 
be dissolved in the fluid, and it was in this manner that I succeeded to my satisfac- 
tion. When the chlorine was introduced into the fluid, the appearance of the hy- 
drate of protoxide of cerium began soon to change, the volume diminished, and a 
heavy, bright, yellow, or rather orange-yellow coloured powder fell to the bottom, 
If, after the chlorine no longer appears to cause any change, the fluid is filtered, a co- 
lourless solution, with the strong odour of hypochlorous acid, is obtained, from which, 
with hydrate of potash in excess, a precipitate is deposited, which collected on a filter, 
is white, or approaching violet. This precipitate begins soon, however, to grow yel- 
low in contact with the air. If the precipitate be again mixed with water and chlo- 
rine introduced, the greater part is dissolved, while a new portion of the yellow-co- 
Joured oxide is formed, and remains undissolved. The filtered solution forms a pre- 
