318 
NARORE 
(AucusT 3, 1899 
operation is continued until the material becomes too 
scanty. ; 
The last horizontal line of fractions, spectroscopically 
examined ina radiant matter tube, shows differences in 
the visible spectrum. For many years I recorded these 
differences in coloured drawings, which have served on 
several occasions to illustrate papers before this Society.? 
In the year 1893 I commenced to record the differences 
between the various spectra by photographing them in a 
spectrograph having a complete quartz train, and since 
that time attention has. chiefly been directed to the vari- 
ations in the number, character and positions of the lines 
and bands in the ultra-violet spectrum ; these are more 
striking than those which are visible, and as they are self- 
recording, results are more rapidly attained. A descrip- 
tion of this instrument is given further on. 
On placing the photographed spectra of one of the 
horizontal lines of earths in order, several differences are 
detected. One striking difference is seen in the be- 
haviour of a group of lines in the ultra-violet. It is 
nearly absent in the end fractions, gradually becoming 
stronger towards the middle, and attaining a maximum in 
the fractions situate about two-thirds towards the right. 
This shows that at least three different bodies are 
present : one, the great bulk, having a nitrate difficult to 
decompose ; another,’ whose nitrate is easiest to decom- 
pose; and a third body, occupying an intermediate 
position, whose nitrate decomposition occurs at temper- 
\ 
Fic. 2. 
atures between that required by the others, but nearer 
that of the nitrate easiest decomposed. 
The above method of fractionation is not so effectual if 
more than two bodies are present. In that case the pro- 
cess fails, in any reasonable time, to yield practically pure 
specimens of more than two out of a group of closely allied 
earths. Thus, if there are three earths—say A, B and C 
—whose positions in reference to the chemical process 
employed are in the written order of sequence, we may 
get a specimen of A as nearly as we please free from B 
and C, and a specimen of C as nearly as we please free 
from A and B, but we cannot get a specimen of B 
practically free from A and C. The law seems to be that 
to obtain practically pure specimens of three closely 
allied earths, it is essential to have recourse to at least 
two different chemical processes. The mere continued 
repetition of the same process will not do, unless, indeed, 
the operations are repeated such a vast number of times 
as to make the approximate expressions no longer 
applicable, even though the substances are chemically 
very close. 
For this and other reasons it is advisable to change 
the method of fractionation after one process has been in 
operation for some time. It is evident that any process 
of fusion, crystallisation or precipitation can only divide 
the mass of material into two parts, a soluble and an in- 
1**On some New Elements in Gadolinite and Samarskite Detected Spec- 
troscopically ” (Rey. Soe. Proc., No. 245, 1886 vol. xl. p. 502). 
NO. 1553. VOL. 60| 
soluble portion, crystals and mother liquor ; and after a 
time a balance of affinities seems to be established, and 
further fractionation appears to do little good. It is 
better then to change the operation. 
Following the diagrammatic scheme, the portions of 
earths containing most victorium are collected together 
and fractionated by the crystallisation of the oxalates from 
a solution strongly acidulated with nitric acid in the 
following manner :— 
Toa boiling acid solution of the nitrate a small quan- 
tity of hot solution of oxalic acid is added. The solution 
remains Clear, and it is only after vigorous stirring that 
a small quantity of insoluble oxalate is formed. The 
whole is thrown on a hot-water filter and slightly washed 
with boiling water. To the boiling filtrate a fresh lot of 
hot solution of oxalic acid is added, and stirred till more 
insoluble oxalate comes down. This is again filtered off, 
and the operations of precipitating, stirring, filtering, 
and washing are repeated, always keeping the temper- 
ature as near the boiling point as possible, until the whole 
of the earths are precipitated. Generally the initial 
earth is divided by this method of fractionation into from 
six to twelve portions. Each of these oxalates is dried, 
ignited, dissolved in nitric acid, and the above-described 
| operations repeated. Photo-spectroscopic tests are con- 
stantly taken during the progress of this fractionation, 
and portions are mixed together according to the data 
thus obtained, as shown on the diagram by the lines 
joining the fractions. The object being to avoid 
lateral spreading as muchas possible, and, while 
concentrating the special line-giving earth, to 
prevent its too great diffusion over a large 
number of fractions. When the fractionation 
by the oxalate method has proceeded for a con- 
siderable time, the fractions rich in victorium 
are collected together and submitted to another 
mode of treatment. 
These fractions are converted into nitrates, 
and a small quantity is thrown out by partial 
decomposition by heat, according to the method 
already described. The filtrate is evaporated 
to dryness and again fused, so as to throw out 
a little more. This operation is repeated as 
long as any soluble nitrate is left. Generally 
from six to twelve portions are thus obtained, 
These form a regular series, differing according 
to the stability of the nitrate under heat. On testing,. 
the victorium is found to concentrate in the centre por- 
tions, being less easily decomposed than the earths of the 
cerium group, and more easily decomposed than those 
of the yttrium group. 
The fractions rich in victorium are converted into sul- 
phates and mixed with a hot saturated solution of potass- 
ium sulphate. The precipitate is dissolved in boiling 
water and mixed with a further quantity of solution of 
potassium sulphate. This produces a small quantity of 
a precipitate. The filtrate from the first precipitate is 
also mixed with fresh potassium sulphate, and the oper- 
ations are repeated, mixing the centre solutions to one lot 
and the side solutions to another, as shown by the lines. 
on the diagram. It is found on photo-spectroscopic 
examination that the earths thrown out on each side are 
poorest in victorium, whilst those in the middle are 
richest. After a time no further concentration is effected 
in this manner, all the earths that can be removed as 
being more or less soluble in potassium sulphate having 
been eliminated. 
In thus describing the method of fractionation, my 
object has been not so much to give a description of the 
plan actually carried out in the laboratory—for the 
details have varied with each operation—but to give an 
intelligible idea of the general manner in which a very 
complicated operation is effected. In the diagram I am 
supposing that one particular substance, victorium, is to 
