Year: 1886

page_text: I, CARL AUER VON WELSBACH, of N° 63 Gumpendorfer Strasse in the City of
Vienna, Austria, Doctor of Philosophy, do hereby declare the nature of this
invention and in what manner the same is to be performed to be particularly
described and ascertained in and by the following statement:-
This invention relates to the treatment of the earths of the rarer metals, such as
minerals containing Cerium, Didymium, Lanthanum, Thorinum and Zirconium, in
order to obtain therefrom solutions suitable for the production of incandescence
Lodies such as are described in the Specifications to Patents No* 15286 of 1885 &
3592 of 1886.
In treating Cerite, Orthite and other similar minerals containing Cerium, Didy-
mium, and Lanthanum, for obtaining these in a separated condition, the minerals
are in the first instance heated to a red heat with free admission of air in those
cases in which iron is contained therein in the form of protoxide, in order to oxidise
the iron of the Cerite compounds to a higher degree and thus avoid various
difficulties in the subsequent operations. This heating process is however only
applicable when the percentage of Cerium compounds is considerable, and when
the mineral is a silicate, and not fusible in ordinary temperatures. A number of
such minerals comply with these conditions; in particular may be mentioned Cerite,
the treatment of which will now be described by way of example.
The raw material as extracted from the earth, is heated to a red heat in lumps
about the size of a fist, with free admission of air, for about an hour.
The mineral is thereby changed in such manner that its original reddish grey
colour has been converted into yellow and that it has taken up oxygen.
The
lumps, while hot, are plunged rapidly into water, whereby they crumble to pieces,
thus greatly facilitating the following disintegrating process in which the material
is crushed partly to powder and partly into small particles of about the size of
hemp seed. The finer particles being separated from the coarser ones, both parts
are stirred in suitable vessels together with ordinary concentrated hydro-chloric
acid, whereby the fiuer particles become decomposed under evolution of heat while

page_text: the coarser particles only become slightly heated. After some days the finer
particles will be entirely decomposed and if the proper proportion of acid has been
used, this will have become entirely exhausted.
The decomposition of the coarser particles takes place more slowly and is only
completed in about a fortnight. It is advantageous to draw off the lye formed
after a few days, to levigate the sludge with water and to mix it with a fresh
supply of concentrated hydrochloric acid until all particles susceptible of decom-
position are decomposed, which can be ascertained by the fact that the original
grains of cerite will have been converted into a friable skeleton mass of silicic
acid. The chloride solution obtained by the above process is precipitated by means
of oxalic acid, and the axalates are washed by decantation and through a filter
cloth and after being pressed dry they are heated to a red heat in shallow iron
pans, but only to such an extent that no complete conversion into the oxides is
effected.
The brown oxides, containing a considerable amount of carbonic acid should, on
being treated in the cold with concentrated nitric acid, dissolve after a short time,
with ebullition, into a dark red liquid. Only when obtained in the above described
manner is the preparation suitable for the following separation process.
The oxides are now stirred together with water in a fire clay vessel and heated
on a steam bath, nitric acid being added in small quantities until a frothing is
observed to take place after every addition.
As the composition of the minerals is very variable, even when taken from
one and the same locality, the quantity of nitric acid cannot be fixed in advance.
The nitrate solution formed after the addition of the nitric acid is digested with
excess of the earths. If, after about 10 hours digesting, it is not converted into a
very fine yellowish red or yellowish powder, but remains of a brown color, nitric
acid must again be added, and this process must be continued until the precipitate
shews the above mentioned color. The supernatant lye is then of an amethyst
color and the precipitate formed is insoluble even in very dilute lye.
If in carrying out the process so much nitric acid has been added that the
yellowish white precipitate is dissolved into a yellowish liquid on the addition of
a large quantity of water, then too much acid has been added and quantities of
the earthy sludge, obtained as above described, mixed with water must be added
until the precipitate obtained has the above inentioned properties.
In this precipitate will be contained the whole of the Cerium of the original
mineral in the form of a compound insoluble in water, while the lye will contain
all the other rare earths.
The Cerium precipitate obtained, after washing, is readily soluble in nitric
acid when heated, and the dark red solution thus obtained is mainly Cerium
nitrate.
The principal constituents of the lye will be the elements of Didymium, (Praseo
dymium and Neodymium) and Lanthanum.
For separating these from each other, the lye separated from the precipitate is
evaporated and treated with nitric acid and ammonium nitrate, and is separated
into its constituents by the formation of the ammonium double nitrates.
In order to perfectly separate the Lanthanum by means of frictional crystallisation
the crystallising process must be repeated several times.
The colorless crystals of Lanthanum ammonium nitrate are chemically pure and
form as solution one of the principal ingredients of the liquid for producing the
incandescence bodies.
In treating zirconium this is reduced to about the size of peas, heated to a white
heat under free admission of air, pulverised and levigated and is then digested for
several days with concentrated pure hydrochloric acid for the purpose of removing
all traces of iron. The original brownish grey powder is by this means converted
into a perfectly white powder, and many of the impurities originally contained in
the zirconium crystals are dissolved. The fine zirconium powder is then washed
and dried and is mixed with double the quantity of calcined. carbonate of soda, and

page_text: after being ground fine, it is subjected to a white heat for about three hours in
a platinum crucible. The cakes of soda melt thus obtained are placed in cold clean
water, when a fine white powder will be precipitated while numerous bodies that
are not useful for the purposes of the invention pass into the mother liquor. The
white powder is washed in water, dried and treated with sulphuric acid under
trituration until a sample heated on platinum clearly shews an excess of sulphuric
acid.
The decomposition of the white powder by sulphuric acid takes place under
considerable heating, and care must be taken that the acid is very gradually added
(the powder remaining perfectly dry) as otherwise a scattering of the mass will
ensue. The powder is then heated to the boiling point of the sulphuric acid whereby
the greater part of the excess of acid will be driven off. After cooling, the powder
is mixed with a large quantity of cold water under stirring, whereby the zirconium
will be dissolved as sulphate together with other bodies. The undissolved.
precipitate is unconverted zirconium and silicic acid. This is separated by filtration
and washed.
The before mentioned solution of zirconium sulphate is precipitated by ammonia
in the cold, and is washed. If this material be now dissolved in nitric acid, so that
no considerable excess of acid occurs, a brilliant white powder will after a short
time be precipitated, which is a peculiar combination of zirconium, containing this
metal in an almost chemically pure condition. The impurities such as iron,
aluinina &c remain in the lye. This reaction is based on the fact that a small
quantity of sulphate of ammonia present in a solution of nitrate of zirconium effects
the separation of the before mentioned compound, completely so when heated, and
partially when cold. As an excess of sulphate of ammonia dissolves the zirconium
precipitate, this is to be avoided.
The precipitate containing the zirconium is almost quite insoluble in water but
soluble in nitric acid when freshly precipitated; when digested with ammonia it is
rapidly converted into dense zirconium hydroxide which is readily separated by
washing. This body is then dissolved in concentrated nitric acid, and the solution
is evaporated on a water bath, producing clear gum like crusts consisting of
zirconium nitrate.
This substance dissolved in water forms a second main constituent of the
incandescence body.
The presence of small quantities of iron such as are contained in the preparation
of zirconium heretofore made is very detrimental to the action of the incandescence
body.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed I declare that what
I claim is
1. The method substantially as herein described of treating Cerite, Orthite and
similar minerals containing Cerium, Didymium and Lanthanum with hydrochloric
acid in the cold, for effecting the separation of the said metals.
2. The method substantially as herein described of separating the Cerium from
the minerals referred to in the preceding claim by treating the chloride solutions
thereof with oxalic acid, heating the oxalates obtained to redness, and treating the
resulting oxides with nitric acid, whereby the Cerium is obtained in the form of
a nitrate solution.
3. In combination with the method for the separation of Cerium from minerals
containing Cerium, Didymium and Lanthanum, referred to in the preceding claim,
the separation of the Didymium and Lanthanum contained in the lye after
separation of the Cerium, by evaporating the lye, and treating the residue with
nitric acid and ammonium nitrate, whereby ammonium double nitrates of the said
metals are obtained in the form of crystals, substantially as herein described.
4. The method substantially as herein described of treating zirconium for the
removal of all traces of iron therefrom, consisting in first heating the zirconium

page_text: to a white heat under free admission of air and then after finely pulverising the
same, treating it for several days with hydrochloric acid.
5. The method substantially as herein described of producing zirconium in a
form suitable for an incandescence body by first converting the zirconium into
a sulphate, and after treating with ammonia dissolving the same in nitric acid,
thereby obtaining a precipitate which, when digested with ammonia and dissolved
in nitric acid and evaporated, produces zirconium nitrate.
6. The method substantially as herein described of separating a zirconium
compound from a solution of zirconium in nitric acid by means of sulphate of
ammonia, whether this be present in the solution from previous processes or be
subsequently added.