26 - ° < TREPORT—1843. - 
cipitate again with caustic potash, which is treated as before with chlorine, and this 
is repeated five or six times, when, finally, hydrate of potash precipitates from the so- 
lution an oxide which does not become in the least yellow by exposure to the air, 
and which suspended in water, is completely dissolved by the introduction of chlorine 
without leaving a trace of undissolved yellow oxide. It was to this oxide, not capa- 
ble of being more oxidized either by the air or chlorine, that I gave the name of 
oxide of Lanthanium, after the production of which, and a nearer acquaintance with 
its properties, another and simpler method was employed to obtain it. The strong 
basic qualities of the new oxide afforded an easy means of separating it from oxide 
of cerium, by treating the red-brown oxide which is obtained when the so-called 
nitrate of protoxide of cerium is heated with nitric acid diluted with 75 to 100 parts 
of water. An acid thus diluted leaves the greater part of the red-brown oxide un- 
dissolved, and from the solution thus obtained the oxide of lanthanium was derived 
which was employed by me in the experiments that I made in the beginning of the 
year 1839. Some of the results which I obtained unfortunately became known to 
the public. When we find the oxide of a body hitherto unknown, nothing, generally 
speaking, is easier than the determination of the qualities of the body, and I there- 
fore expected to be able to give a complete account of my experiments in a very 
short time, but on this point I was much deceived. That which, in the first place, 
gives any value to chemical investigation, is the certainty that the object investigated 
is pure, that is to say, free from foreign substances. I had not made much progress 
in the details of my inquiry, when it appeared that what I at first considered to be pure 
oxide of lanthanium, was, in point of fact, a mixture of the new oxide with a number 
of other substances, so that in the course of the experiments I succeeded in sepa- 
rating no less than seven different substances, one after the other. The first, to my 
great surprise, was lime, in no considerable quantity ; and I have found that sulphate 
of lime and sulphate of potash forms a double salt sparingly soluble. Afterwards the 
following oxides were successively separated, and by the application of different 
means, namely, oxide of iron in large quantities, of copper, tin, nickel, cerium, and 
something resembling uranium, &c.; but even the oxide which remained after the 
separation of all these substances, left me in nearly the same position which I held 
at the commencement of the researches, so that, although at the end of the year 
1839 I had already been fortunate enough to obtain oxide of lanthanium tolerably 
pure, it was not until the beginning of the following year that I was able, with any 
facility, to obtain a larger quantity of it; but, notwithstanding all my efforts, [ have 
not yet succeeded in discovering any method of separating, with any degree of ana- 
lytical accuracy, lanthanium from cerium, &c. 
Oxide of lanthanium, as pure as I have hitherto been able to obtain it, possesses 
the following properties :—It is of a light salmon colour, or nearly white, but not in 
the least reddish or brown, and retains its appearance unchanged when heated either 
in open or close vessels at a red or white heat: the slight colour seems to proceed 
from a small remnant of some foreign substance. The oxide, although just previously 
ignited to a white heat, soon changes its appearance in water, becomes snow-white, 
more bulky, and after twenty-four hours in the ordinary temperature of the air, be- 
comes changed to a hydrate easily suspended in water. With boiling water this 
change takes place very quickly, and begins immediately; the newly heated oxide as 
well as the hydrate immediately restores the blue colour to moist reddened litmus 
paper. Oxide of lanthanium is easily dissolved by acids even much diluted. Salts, 
when they are formed by the combination of the oxide of lanthanium with un- 
coloured acids, are absolutely colourless, as well as the most concentrated solutions 
of the same. Salts of lanthanium have a sweet, slightly astringent taste, and the 
solution of them can be completely separated from oxide of lanthanium by the addi- 
tion of sulphate of potash in sufficient quantity, because the double salt formed by 
sulphate of oxide of lanthanium and sulphate of potash is quite insoluble in a solu- 
tion saturated with sulphate of potash. The atomic weight of oxide of lanthanium, 
as it has hitherto appeared in most instances, has oscillated about 680, a number 
which, however, possesses no scientific value, when, as I have already remarked, an 
absolutely pure oxide has not yet been obtained. 
Of the salts produced, I will only briefly describe a few of the most characteristic. 
