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TRANSACTIONS OF THE SECTIONS, 31 
during the following autumn and winter, and thereby was not only enabled to con- 
firm the correctness of my former observations, but made the unexpected discovery 
that, as was the case with oxide of cerium, what chemists have hitherto considered 
as yttria, does not consist of one oxide only, but is fer the most part to be regarded 
as a mixture of at least three, of which two appear to be new and hitherto unknown, 
all possessing the greater number of their chemical characters in common, for which 
reason chemists have so readily overlooked their real differences. 
The characters which are peculiar to these oxides, and distinguish them from all 
others, are,—1st, that although powerful salt bases, all more so than glucina, they 
are insoluble in water and in caustic alkalies, but on the other hand soluble, even 
after having been exposed to a strong heat, in a boiling solution of carbonate of 
soda, although after a few days the greater part separates from its solution in the 
form of a double salt ; 2ndly, that combined with carbonic acid, they are largely 
soluble in a cold solution of carbonate of ammonia, and that when such solution is 
saturated with them, a double salt of carbonate of ammonia and the above carbo- 
nates immediately begins to separate, and that in such quantity, that after a few hours 
very little oxide remains in solution; which explains the observations of several 
chemists, that, as they express themselves, yttria sometimes dissolves freely, somes 
times scarcely at all, in carbonate of ammonia: further, that the salts of these oxides 
have a sweet taste, and that the sulphates dissolve with more difficulty in warm than 
in cold water, without its following that they form double salts with sulphate of potash, 
which are insoluble in a saturated solution of the latter. 
If the name of yttria be reserved for the strongest of these bases, and the next in 
order receives the name of oxide of terbium, while the weakest be called oxide of 
erbium, we find the following characteristic differences distinguishing the three sub- 
stances:—The nitrate of yttria is extremely deliquescent, so much so that if a small 
portion of a solution of that salt be left for weeks in a warm place, the salt produced 
will not be free from humidity. The solution of nitrate of oxide of terbium, which 
is of a pale reddish colour, soon evaporates, leaving a radiated crystalline mass, which 
does not change in air unless it be very damp. The crystals of sulphate of yttria are 
colourless, and remain clear and transparent for weeks in air at a temperature vary- 
ing from 86° Fahr. to 158° Fahr., while a solution of sulphate of oxide of terbium 
yields by evaporation, at a low temperature, a salt which immediately effloresces to a 
white powder. Oxide of terbium, the salts of which are of a reddish colour, appears, 
when pure, to be devoid of colour, like yttria. Oxide of erbium differs from the two 
former in its property of becoming of a dark orange yellow colour when heated in 
contact with air, which colour it is again deprived of, with a trifling loss of weight, 
_ by heating it in hydrogen gas; and it is to the presence of oxide of erbium that 
yttria owes its yellow colour, when prepared as hitherto directed: and it is more- 
over probable, that in all those cases where a colourless yttria has been supposed to 
have been obtained, the presumed yttria has consisted for the most part of glucina, 
at least before it was known how to separate the last earth completely. 
_ The sulphate and nitrate of the oxide of erbium are devoid of colour, although 
the solution of the oxide in acids is sometimes yellow, and the sulphate does not 
effloresce. 
~ These and a number of other less remarkable differences between the three oxides, 
appear to me to place beyond a doubt that what we have hitherto obtained and 
described as yttria, is neither more nor less than a mixture of these three bases, at 
least such is the case with yttria prepared from gadolinite, cerine, cerite, and orthite, 
but as I have not yet had the good fortune to discover any tolerably easy or certain 
mode of obtaining the one or the other oxide chemically pure, I shall confine myself 
for the present to this short statement of facts. 
- I proceed to make known two easy methods by which chemists may prove the 
correctness of the above statements. If caustic ammonia in small quantities at a time 
be added to a solution of ordinary yttria in muriatic acid, and the precipitate follow- 
ing each addition be washed and dried apart, we obtain basic salts, of which the last 
precipitated are colourless, and contain yttria only. Going backwards in reyerse 
order from these last, we find the precipitates becoming nearly transparent, reddish, 
and containing more and more oxide of terbium, while the furst precipitates contain 
