Improvements in the Manufacture of Aluminium and its Alloys.
Year: 1889

page_text: Date of Application, 16th Jan., 1889
Complete Specification Left, 18th Nov., 1889-Accepted, 16th Jan., 1890
PROVISIONAL SPECIFICATION.
Improvements in the Manufacture of Aluminium and its Alloys.
I, WILHELM DIEHL of Karlstrasse, Berlin in the German Empire, Chemist, do.
hereby declare the nature of this invention to be as follows:-
For the separation of aluminium and its alloys from its fluoride by electric process
I produce a bath by melting the compound fluorides of aluminium and of alkali
metals together with as much chloride of an earth alkali metal. (chloride of barium,
strontium, calcium, magnesium) as is required to form with the fluoride of alkali
metal, fluoride of the earth alkali metal and chloride of the alkali metal; more
alkaline chloride being added if requisite. The quantity of the chloride of the earth
alkali metals to be added is different for each of them and must be found out
empirically. Its excess is washed out and this residue may be melted over again
with alkaline chloride, for the production of aluminium.
For the same purpose the compound fluorides of aluminium and alkali metals or
the compound fluorides of aluminium and of earth alkali metals, resulting from the
aforesaid washing operation of the molten mass may be melted without any chloride,
fluorides of barium, strontium, calcium, magnesium being added thereto. The molten
mass thus obtained is exposed to the action of a constant electric current at the
melting temperature. As electrodes I employ two carbons or a carbon electrode
as the positive and a metal one as the negative. In the former case aluminium is
produced and in the latter its alloy with the respective metal.
In order to prevent the recombination of the metal dispersed in the molten mass
with the halogen a fire proof diaphragm non porous is provided nearly reaching to
the bottom of the vessel. This diaphragm has oblique slits through which the positive
current passes upwards to the negative electrode.
When
To separate the inolten mass by chemical metallurgic process it is reduced to
powder and piled up with one of the metals K, Na, Mg, Zu, Cd in a crucible which
must be tightly closed and luted and then exposed to a high temperature.
cold the aluminium may be readily separated from the product which contains the
fluorides of the metal employed. Aluminium in a pure state may also be produced
from its fusible alloys, obtained by electrolysis. For this purpose these alloys are
separated by eliquation into two bodies one containing more aluminium than the
other, the latter being again employed as electrode, the former being melted with
chemical substances which affect the other metal but not aluminium. During the
electrolysis the metal may be in a molten state or not; in the former case its conduit
of communication is insulated from the molten mass.
The alloys of aluminium with lead, bismuth, tin, antimony are separated by heat
into two kinds of alloys, the one poor and fusible, the other rich in aluminium. The
latter is melted with sulphur, pressure being applied, or with polysulphides (bodies
yielding sulphur) and in this way aluminium is produced in addition to the sulphides
of the respective metal.
The alloys of iron with aluminium which are immediately produced by electrolysis
as well as those of lead, nickel, cobalt, are melted together with certain fusible
mixtures of salts containing nitrates which either oxidate the lead, supposing the
alloy to be lead, or only cause a separation of the other alloys into one difficult to
melt and another which is fusible being aluminium in an almost pure; state.
compound salts are :—
1. Chlorides of alkali metals with nitrates of alkali metals.
2. Chlorides of the earth alkali metals with nitrates of the alkali metals.
3. Chlorides of alkali metals with nitrates of the earth alkali metals.
Such

page_text: 5. Nitrates of alkali metals, nitrates of the earth alkali metals, or their compound
Balts.
The alloys of aluminium with zinc or cadmium produced by electrolysis are
separated by distillation into aluminium and zinc or cadmium. For this purpose an
hermetically closed crucible is employed a clay pipe passing through the bottom of
the same. Upon applying heat to the crucible aluminium will remain behind in it
and zinc or cadmium will distil through the clay pipe into a suitable receiver placed
underneath.
The compound fluoride of aluminium and of the earth alkali metals may be obtained
by adding a watery solution of an earth alkaline salt and of an aluminous salt in
proportion to a watery solution of fluoride of natrium, or by causing a solution of
nitrate of aluminium to act upon fluoride of an earth alkali metal, beat being
-applied.---
500
Na, Dº. + × Na, Do̟ and melt them together in a crucible. When melted, they are
allowed to cool down, and are then ground, and thoroughly washed in water to get
rid of all traces of the sulphate.
The fluoride thus formed will contain, for one molecule of aluminium fluoride, one
molecule of alkaline fluoride, Al, F, 1 Na F.
This compound fluoride is now melted with an alkaline chloride, say, chloride of
sodium, in proportion about the chemical equivalent of the aluminium fluoride, with
as much fluor spar as the molten mass will take up, and while in a molten state,
the mass is submitted to a current of electricity, with the result, that aluminium
will collect on the negative pole, and chlorine will be liberated at the positive pole.
In additoin, a certain amount of alkali (e.g. sodium) fluoride, will be formed in the
molten mass, as indicated by the following formula :—Al¸ F¸ Na F + 6 Na Cl =
Al, 7 Na F + 6 Cl.
This sodium fluoride, if melted with anhydrous alum, will form the double
fluoride Al, F, 1 Na F., and will be in a condition to be subjected to electrolysis, as
before explained, after the mixture has been thoroughly washed, and the alkaline
chloride added thereto.

page_text: In place of the anhydrous alum, a watery solution of nitrate of alumina, Al, (No,)*,
may be used for the purpose of producing the compound fluoride of aluminium to
be treated.
I
may also effect my purpose by taking the compound fluorides of aluminium and
alkali metals, and melting them with fluoride of barium, without any chloride.
Al, F. 6 Na F + 3 Ba F₂ = Al, + 3 Ba F, + 6 Na F + 6 F.
The various compounds obtained by the above means are subjected to the action
of the electric current in a crucible heated in a furnace.
In the accompanying drawing, I have shewn, in vertical section, the crucible
which I prefer to use in carrying out my invention. In this figure, A is the
crucible, placed in a furnace B. (is a diaphragm reaching nearly to the bottoin of
the crucible, for the purpose of preventing the recombination of the separated metals
with the halogen (Fluorine or chlorine). D is a cover provided with a plugged
opening E. F is the positive electrode (anode) of retort carbon, and G is the negative
electrode (cathode), which may also be of carbon, but preferably of some suitable
metal, as lead, iron, or copper. When the electric current is passed through the
mass, aluminium will be deposited in a pure or nearly pure condition on the cathode,
if of carbon, but if of metal, an alloy will be formed of aluminium and the metal of
the cathode. From this alloy, aluminium in a pure state may be obtained in any
convenient manner.
When employing a retort carbon as cathode, the desired quality of the aluminium
is not obtained, nor the desired output, as compared with the electrical power
expended; it is therefore preferable to produce, first, an alloy by electrolytical
process, from which the aluminium can be afterwards separated, by means of
commonly known processes. The treatment of these alloys, however, will vary
according to circumstances.
Thus, if lead be the metal used, the lead unites with a large proportion of
aluminium to form an alloy containing about 75% aluminium, which will rise to
the top of the molten lead, as it is lighter. The lead, which is easily melted, separates
readily from the aluminium, and can be used again in the process.
The aluminium alloy may also be separated by chemical agents, which change the
lead chemically, but leave the aluminium intact.
Sulphur is suitable for this purpose, as it changes the lead into sulphide of lead,
and leaves the aluminium unchanged.
Nitrates of the alkalis, or of the earth alkalis, are also suitable, which oxidize the
lead, but do not take effect upon the aluminium. As byo-products, in the first case,
alkali nitrite and oxide of lead are formed, and in the latter case, alkaline earth and
lead super-oxide.
If either of the metals iron, copper, cobalt or nickel, is employed as the cathode,
the currents must be so regulated, that an alloy rich in aluminium shall be
obtained from the cathode. This easily fusible alloy will be separated, by careful
fusion, into a crystalline alloy difficult of fusion, and containing little aluminium, and
a pure or nearly pure aluminium, comparatively easily fusible. This separation
proceeds more effectually when it takes place in combination with certain salts
which will not undergo chemical change, but only facilitate the separation.
As an example, when employing, say, iron as cathode, an alloy is obtained con-
taining about 90% aluminium, and which, on fusion, separates into pure aluminium,
and an alloy containing aluminium.
The process may be formulated as follows, expressed in percentages :-

page_text: As salts, the following, for example, are suitable :
Alkaline chlorides in union with nitrates of the same.
Earthy alkali chlorides
Alkali chlorides.
Earthy alkali chlorides
Alkali nitrates
alkali nitrates.
"
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13
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Earthy alkali nitrates.
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Alkali nitrates.
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دو
The electrolytically obtained iron alloy can also be separated by means of sulphur,
in a closed vessel, at the melting temperature of aluminium, into sulphide of iron
and aluminium. In open-vessels,-the-sulphur vaporizes without taking effect on
the iron.
From the alloys of aluminium with zinc or cadinium, the latter metals are removed
by distillation in a clay crucible, well closed and luted, and through the bottom of
this crucible, a clay pipe is passed. On heating the crucible with its contents, the
aluminium will remain, whilst the zinc or cadmium will distil over into a receiver
placed below.
The compound fluorides of aluminium & of the earth alkali metals may be obtained
by mixing aqueous solutions of alumina salts and the earth alkali salts, with solutions
of alkaline fluorides, 12 Na F + 3 Ba Cl, + Al, Cl. = Al, F. +3 Ba F, + 12 Na. Cl.
The fluor spar (calcium fluoride) above mentioned, is added to the molten mass
in order to prevent the destructive effect on-the-crucible, of the alkaline fluoride which
is formed. This calcium fluoride combines with the alkaline fluoride, and-forms a
more-or-less-neutral.compound.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I-
claim is
1. The process herein described for obtaining aluminium and its alloys, and con-
sisting in melting together fluorides of alkali metals, or compound fluorides of
alkali metals and aluminium, and anhydrous alum, in or about the proportions given,
with the addition of anhydrous alkali sulphate; cooling, grinding, and washing the
mass; then melting the washed mass with chlorides of alkali metals in equivalent
proportions, and subjecting the molten mass to electrical action, whereby the aluminium,
is deposited upon the negative pole, chlorine is liberated at the positive pole, and an
alkali fluoride is formed in the molten mass, which alkali fluoride, when melted with
anhydrous alum or mixed with a watery solution of nitrate of aluminium, and washed,
will form a compound fluoride of aluminium, which may be treated as above described,
for obtaining the aluminium.
2. A bath from which to obtain aluminium by electrolysis, composed of
aluminium fluoride, alkali fluoride, and barium fluoride, as heroin described, without
any chloride.
3. The modes above described of separating aluminium from its alloys, produced in
the manner above set forth
Dated this 19th doof N 1000