Improvements in the Manufacture of Aluminium and other Metals.
Year: 1889

page_text: Date of Application, 24th Oct., 1889
Complete Specification Left, 25th Aug., 1890-Accepted, 4th Oct., 1890
PROVISIONAL SPECIFICATION.
Improvements in the Manufacture of Aluminium and other Metals.
I, DOUGLAS DIXON, of 65 Hereford Road, Bayswater, in the County of
Middlesex, Civil Engineer, do hereby declare the nature of this invention to be as
follows:
:-
My invention relates to improvements in the methods of manufacturing aluminium
and other metals, and in apparatus therefor, the object being the reduction of metals
by combined electrical, thermal and chemical reactions.
I effect this by the electrical decomposition of molten halogen salts, and the
chemical reaction of one of the resulting elements on the oxide of the metal to
be reduced, or on a suitable mixture of such oxide with carbonaceous material, while
the other element reacts on the resulting compound.
According to the nature of the reagent and the metal to be reduced, the product
of the anion and the oxide may be brought continuously into the presence of the
nascent cation, or the oxide may first be brought in contact with the nascent
cation and the oxide of the reducing metal resulting from the reaction be in turn
reconverted by the anion.
The halogen element set free at the anode can be made to react upon the oxide,
or a suitable mixture of the oxide with carbonaceous material, and produce a salt
which is conveyed continuously, in a liquid or vapour form, to the surface of the
bath at the cathode where it is decomposed by the inetallic element as it is liberated
at this point.
The bath may be composed of one or more of the salts of the alkaline metals, of
calcium, of magnesium, of aluminium or of ammonium, the nature of the salt
or salts and the proportions thereof used varying according to the conditions as to
temperature of fusion, electrical resistance, fluidity, specific gravity etc. of the bath and
active electrolyte necessary for the particular metal to be reduced and for fluxing or
causing the globules of metal to run together as produced.
As the least electro-positive metallic element in the bath or the one for which its
halogen element has the least affinity is the one which will be set free from its
element, for example chlorine or bromine by the current, its chemical affinity for
the halogen element must be greater than that of the metal to be reduced, whilst
its specific gravity as compared with that of the bath must be such that it will rise to
the surface while the metal being reduced should sink to the bottom.
With a sodium or lithium salt as the active electrolyte, it will be found that
the less electro-positive metals of the alkaline earths, magnesium, manganese and
aluminium &c. can be reduced, while the more electro-positive potassium salts serve
to lower the temperature of fusion and specific gravity of the bath, the fluorides of
each acting as fluxes for the metal produced.
In like manner with a calcium salt as the active electrolyte the less electro-positive
metals, such as magnesium, manganese, aluminium and zinc can be reduced, while
with a magnesium salt as the active electrolyte, manganese, aluminium, zinc, &c. may
be reduced.
For example with chloride of magnesium as the active electrolyte in a bath con-
taining a suitable proportion of chloride of sodium and with aluminium as the metal
to be produced the reaction at the anode will be Al₂ O2 + 3 C + 6 Cl + 2 Na Cl =
Al, C. 2 Na Cl + 3 CO; 3 Mg Cl, being decomposed by the current to supply the
chlorine. The reaction at the cathode will be Al, Cl + 2 Na Cl + 3 Mg = 2 Al +
3 Mg Cl, 2 Na Cl.
The oxide or the mixture of the same with carbonaceous material may be submerged

page_text: in the bath at the anode in which case it should be separated from the cathode by a
porous or perforated partition or cell. If there are ingredients in the bath which
form volatile double salts with the salt of the metal in the oxide, these will be
volatilized and can readily be condensed into the liquid form and run into the com-
partment in which the cathode is placed; or a mixture of the oxide and
carbonaceous material; or a mixture suitable for the formation of a double salt
may be placed in a suitably heated retort or vessel above or beside the bath and the
halogen element conveyed into it from the anode by a suitable duct or pipe. In this
case the partition or cell separating the electrodes, need only extend downwards
beneath the surface of the bath to a sufficient depth to prevent the gaseous balogen
element from getting into the cathode compartment. The newly formed salt need
not be volatilized, but can be run out of the retort in a liquid state, as it is formed
at a much lower temperature than is required to volatilize it readily, but it is necessary
to prevent any excess of the halogen element, and the carbonic oxide generated
during the reaction, from passing into the cathode compartment with the salt.
this purpose a trap may be provided at the part of the retort where the liquid salt
collects and through which trap such salt which acts as a seal, trickles as formed. In
the case of a salt that does not readily liquify, as for example the single chloride of
aluminium whether formed in a bath, or in a retort, it may be separated from the
gases mentioned by condensation and be precipitated upon the bath within the cathode
chamber.
For
The vessel containing the bath may be constructed of suitable material such as
iron, steel, nickel, plumbago, fireclay, or basic material, according to the nature of the
bath and the metal to be reduced, or the vessel may be lined with carbonaceous.
aluminous, magnesic or basic material, as required by the operation.
The cathode may be of iron, steel, nickel, carbon, aluminium, or copper according
to the conditions of any particular case or in some cases the vessel itself may
be advantageously used as one of the electrodes. The anode may advantageously
be of gas carbon, and in some cases pieces of coke, charcoal, or gas carbon may be
packed around and in contact with it, in order to give a greater surface or to furnish
reducing material to assist the reaction. The partitions or cells may be of noncon-
ducting material, and when perforated, the holes may be diagonal or inclined to the
surface and arranged to lead upward towards the anode to prevent the rising halogen
gas or carbonic oxide or both and the sinking metallic particles from passing
through them.
In cases where the metallic reagent for example magnesium, liberated by the
current has an affinity for oxygen so much greater than that of the metal to be
reduced for example aluminium as to reduce its oxide without the intermediate
agency of the halogen element then this oxide may be fed on to the surface of the bath
at the cathode where it will be decomposed by the nascent cation, the reduced metal
sinking to the bottom of the bath while the resulting light oxide of the reducing
metal will float over to the anode where it will in turn be re-converted by the nascent
halogen to its original state and mingle with the bath. In this case it is desirable to
have a partition between the electrodes from the bottom upwards to within a short
distance of the surface of the bath, or if continued higher than the surface it
must be porous or perforated near the surface. The anode compartment may be
filled with lumps of carbon in contact with the electrode to assist in the reduction of
the oxide.
Dated sh: 00-1

page_text: COMPLETE SPECIFICATION.
Improvements in the Manufacture of Aluminium and other Metals.
I, DOUGLAS DIXON, of 65 Hereford Road, Bayswater, in the County of Middlesex,
Civil Engineer, 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 :-
My invention relates to improvements in the manufacture of aluminium and other
metals, and in apparatus therefor, the object being the reduction of metals by combined
electrical, thermal, and chemical re-actions.
According to this invention I effect the reduction of the compound or ore of
aluminium or other metal to be treated by the electrolytical decomposition of a
molten halogen salt, one of the elements of which is caused to react on the oxide or
other suitable compound of the metal, (hereinafter referred to as an oxide) or on
a suitable mixture thereof with carbonaceous material, while the other element of
the salt is caused to re-act on the resulting compound, these operations taking place
continuously in the manner hereinafter described."
According to the nature of the re-agent or halogen salt used and the metallic oxide
to be reduced, the product of the anion and the oxide may be brought either con-
tinuously into the presence of the nascent cation, or the oxide may first be brought
in contact with the nascent cation, and the oxide of the reducing metal resulting from
the re-action, be in turn reconverted by the anion.
In the former case the halogen element set free at the anode is caused to re-act
upon the oxide, or a suitable mixture of the oxide with carbonaceous material, and
produce a salt which is conveyed in a continuous manner in a liquid, or a vapour form,
to the surface of the bath at the cathode, where it is decomposed by the metallic
element as it is liberated at this point by the decomposition of the halogen salt.
The bath or electrolyte to be electrolytically decomposed, may be composed of one
or more of the halogen salts of the alkaline metals, of calcium, of magnesium, of
aluminium, or of ammonium, the nature of the salt, or salts, and the proportions
thereof used, varying according to the conditions as to temperature of fusion,
electrical resistance, fluidity, specific gravity, etc. of the bath, and active electrolyte,
necessary for the particular metal to be reduced, and for fluxing or causing the
globules of metal to run together as produced.
As the least electro-positive metallic element in the bath or the one for which
its halogen element has the least affinity, is the one which will be set free from its
element, for examples, chlorine or bromine, by the current, its chemical affinity for
the halogen element must be greater than that of the metal to be reduced, whilst its
specific gravity as compared with that of the bath must be such that it will rise to
the surface of the bath while the metal to be reduced from the oxide treated should
sink to the bottom.
With a sodium or lithium salt as the active electrolyte, it will be found that the
less electro-positive metals of the alkaline earths, magnesium, manganese, aluminium
and so on, can be reduced, while the more electro-positive potassium salts serve to
lower the temperature of fusion and specific gravity of the bath, the fluorides of either
of the metals mentioned acting as a flux for the metal produced.
In like manner with a calcium salt as the active electrolyte, the less electro-positive
metals, such for examples as magnesium, manganese, aluminium and zinc can be
reduced, while with a magnesium salt as the active electrolyte, manganese, aluminium,
zine, and other less electro-positive metals may be reduced.
For example, with chloride of magnesium as the active electrolyte in a bath
containing a suitable proportion of chloride of sodium, and with a mixture of oxide
of aluminium with carbon for the production of aluminium, the re-action at the anode
will be Al, 0, +3 C + 6 CI+ 2 Na Cl = Al, C, 2 Na Cl + 3 CO, three molecules of
chloride of magnesium (= Mg (2) being decomposed by the current to supply the
chlorine. The re-action at the cathode will be Al, Cl + 2 Na Cl + 3 Mg= 2 Al +
3 C

page_text: The oxide, or the mixture of the same with carbonaceous material, can be submerged
in the bath at the anode in which case it should be separated from the cathode by a
porous or perforated partition or cell. If there are ingredients in the bath which
form volatile double salts with the salt of the metal in the oxide, these double salts
will be volatilised and can be readily passed into the compartment in which the
cathode is placed. Or a mixture of the oxide and carbonaceous material; or a
mixture suitable for the formation of a double salt, can be placed in a suitably beated
retort or vessel either above or beside the bath, and the halogen element conveyed
into it from the anode, by a suitable duct or pipe. In this case the partition or cell
separating the electrodes, need only extend downwards beneath the surface of the bath
to a sufficient depth to prevent the gaseous halogen element from passing into the
cathode compartiment. The newly formed salt need not be volatilised, but can be run
out of the retort in a liquid state, as it is formed at a much lower temperature than is
required to volatilise it readily, but it is necessary to prevent any excess of the
halogen element and the carbonic oxide generated during the re-action, from passing
into the cathode compartment with the salt. For this purpose a trap may be provided
at the part of the retort where the liquid salt collects and through which trap such
salt, which acts as a seal, trickles as formed. In the case of a salt that does not
readily liquify, as for example, the single chloride of aluminium, whether formed in
the bath or in a retort, it may be separated from the gases mentioned, by condensation,
and be precipitated upon the bath within the cathode chamber.
The vessel containing the bath may be constructed of suitable material such as
carbon iron, steel, nickel, plumbago, fire-clay, or basic material, according to the
nature of the bath and the metal to be reduced, as well understood, or the vessel
may be lined with carbonaceous, aluminous, magnesic, or basic material, as required
by the operation.
The cathode will usually be of carbon but may be of iron, steel, nickel, aluminium,
or copper according to the conditions of any particular case; in some cases the
vessel itself may advantageously be used as one of the electrodes. The anode may
advantageously be of gas carbon, and in some cases pieces of coke, charcoal, or gas
carbon may be packed around and in contact with it, in order to give a greater
surface or to furnish reducing material to assist the reaction. The partitions or cells
may be of non-conducting material, and when perforated, the holes may be diagonal
or inclined to the surface and arranged to lead upward towards the anode for the
purpose of preventing the rising halogen gas, or carbonic oxide, or both, and the
sinking metallic particles, from passing through them.
In the accompanying drawings,
Fig. 1 is a vertical section of apparatus suitable for the manufacture of aluminium
according to this invention.
1 is a vessel of suitable material, for example a plumbago crucible, arranged within
a chamber 2 and heated by combustion of fuel on a grate 3. In the example shown,
the vessel itself forms the negative electrode. 4 is a retort secured in place upon the
vessel 1 and provided with a removable cover 5 for the introduction of a suitable
mixture of alumina, chloride of sodium, and carbon such as commonly employed
for the preparation of double chloride of aluminium and sodium. 6 is an exit pipe
for carbonic oxide generated during the reaction.
lower part of which serves to prevent liberation of the negative element of the bath
7 is a porous perforated cell the
directly below the anode. The upper part of the cell serves as a partition to separate
the negative electrode 1 from the positive electrode 8, and is formed with a flange 9
having a depending rim that dips into an annular groove 9" in the bottom of the
retort 4 for the purpose of forming a trap therewith as hereinbefore mentioned. The
positive electrode 8 can be of carbon and dips through the cell 7 into the bath, its
upper part being coated with refractory material, for example a fire-clay pipe, that
bears upon the cell 7, openings 10 being left between the two for the passage of the
gaseous anion from the vessel 1 to the retort 4. 11, 11" are dampers for regulating
the heating of the vessel 1 and retort 4 by controlling the flow of hot gases and
products of combustion from the fire place to the chimney flue 12. 13 is a condenser

page_text: into which the carbonic oxide passing off by the pipe 6 can be led, if necessary,
for the purpose of removing therefrom any volatile chloride that may be carried
off by it.
For the production of aluminium I proceed as follows:-
Into the vessel 1 is introduced a suitable mixture of say about 35 parts by weight
of chloride of magnesium, and 25 parts by weight of chloride of potassium to which
may be added about 40 parts by weight of chloride of sodium, the chloride of potas-
sium being added to reduce the fusing point and specific gravity of the bath produced
by the fusion of the mixture, and the chloride of sodium being used as a diluent, but
this salt is not indispensable. I do not limit myself to the proportions mentioned
as satisfactory results can be obtained when they are varied within wide limits. To
the mixture may be advantageously added from about 3% to 5% of a fluoride, for
examples fluoride of calcium of potassium sodium or of aluminium. Into the retort 4
is introduced an intimate mixture of alumina chloride of sodium and powdered
carbon. The vessel 1 is then heated to about 800° C. or sufficient to keep the mixture
therein in a molten state, and the vessel 1 and positive electrode 8 are connected to
the negative and positive poles respectively of an electric generator. Satisfactory
results can be obtained with a difference of potential between the electrodes of from
about 6 to 8 volts. The chloride of magnesium is thereby electrolytically decomposed,
the magnesium being liberated at the cathode and rising to the surface of the
bath, whilst the chlorine liberated at the positive electrode passes into the retort
through the openings 10 and reacts upon the mixture therein producing a double
chloride of aluminium and sodium according to the first formula hereinbefore given.
The retort 4 is heated to such a temperature so as not to volatilize the double chloride
but maintain it in a liquid state and allow it to flow through the trap at 9, 9ª on to the
surface of the bath where it is reduced by the nascent magnesium according to the
second formula herein before given, aluminium being obtained and chloride of
magnesium being reproduced. The several reactions herein before mentioned take
Instead of the bath
place continuously during the continuation of the process.
herein described by way of example, I can use a bath of chloride of sodium containing
say about 20% of chloride of potassium and 3% to 5% of fluorides, such as those
before mentioned. In this case the aluminium compound will be reduced by the
sodium liberated at the cathode, chloride of sodium being reproduced.
In Fig. 2 which is a similar view to Fig. 1, an independent negative electrode 1ª
is used, and the retort 4 which is shown placed above and to one side of the vessel 1,
is connected to such vessel by a pipe 10. In this example, the retort is shown as
intended to be charged with a mixture for the production of the single chloride of
aluminium (Al, Cl) and is heated to a sufficient extent to volatilise the chloride and
cause the same to pass by the exit pipe 6 to a condenser 15 wherein it is condensed
and separated from the carbonic oxide with which it was produced and allowed to
precipitate as powder through the lower end of the condenser and fall upon the
surface of the bath in the vessel 1 where it is decomposed as in the previous arrange-
ment. When the retort is used to make double chloride of aluminium it is provided
with a trap and outlet pipe at the bottom for conducting the liquid double chloride to
the cathode compartment.
The vessel 1 is provided with a partition 7ª that simply dips below the surface of
the bath.
In Fig. 3, which is also a similar view to Fig. 1, the vessel 1 is constructed with a
perforated diaphragm 7 that forms with the vessel a receptacle for the mixture of
alumina and carbon which in this case will be immersed in the molten bath contained
in the vessel. With this arrangement the chloride of aluminium produced in the
receptacle by the reaction of the chlorine liberated at the positive electrode, will pass
directly into the bath in the cathode compartment where it will be reduced as in the
previous arrangements.
In cases where the metallic re-agent or cation for example magnesium, liberated
from a suitable salt thereof, for example a halogen salt, by the current, has an affinity
for oxygen so much greater than that of the metal to be reduced, for example

page_text: aluminium, as to reduce the oxide of this metal without the intermediate agency
of the halogen element and without forming an aluminate, then this oxide may be fed
on to the surface of the bath at the cathode where it will be decomposed by the
nascent cation, the reduced metal sinking to the bottom of the bath while the
resulting light oxide of the reducing metal will float over to the anode where it
will in turn be re-converted by the nascent halogen to its original state, and mingle
with the bath where it will be again decomposed, these operations taking place in a
continuous manner during the process.
Fig. 4 is a vertical section of apparatus suitable for carrying out this method of
producing aluminium. 1 is the vessel containing a bath consisting of suitable
proportions of chloride of magnesium and chloride of potassium say about 95 parts
by weight of the former to 75 parts by weight of the latter but those proportions can
be varied. To the bath may be added a small proportion of fluoride to serve as a
"flux" as well understood. 7 is a cell perforated at the upper part below the surface
of the bath, and provided with a cover having a charging aperture 15" through which
alumina is introduced, and with a hole through which the negative electrode 1ª is
introduced. The vessel 1 serves as the positive electrode. With this arrangement
the magnesium liberated in the cathode compartiment reduces the alumina introduced
therein according to the following formala 3 Mg + Al, O₁ = Al₂ + 3 Mg 0.
-
The aluminium sinks to the bottom of the cell 7 and the magnesia (Mg O) passes
into the outer portion of the vessel 1 where it is reconverted into chloride of magne-
sium by the chlorine liberated from the positive electrode, thus 3 Mg 0 + 6 Cl =
3 Mg C, +3 0.
=
These reactions take place continuously during the process. The tension of the
current used must be sufficiently low to prevent decomposition of the potassium salt in
the bath.
This process can be carried out in a vessel with electrodes arranged as shown in
Figs. 2 and 3. with or without the diaphragm 7 or 7.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed declare that what I
claim is :-
1. For the purpose of producing a metal, for example aluminium, from a compound
thereof, electrolytically decomposing a molten halogen salt, and causing one element
thereof to react on the metallic compound or upon a suitable mixture thereof with
carbonaceous material, while the other element of the salt reacts upon the compound
so produced, these reactions taking place continuously in the manner set forth.
2. The herein described process of producing a metal for example aluminium from
a compound (or ore) thereof by subjecting such compound (or ore) or a mixture
thereof with carbonaceous material, to the action of the halogen element set free by
the electrolytical decomposition of a molten halogen salt, and conveying the resulting
halogen salt or compound thus produced, to the bath of molten halogen salt wherein
it is subjected to the reducing action of the nascent cation, these operations taking
place continuously in the manner set forth.
3. The herein described process of producing aluminium or other metal from a
compound (or ore) thereof by subjecting the same to the reducing action of the
nascent metallic element liberated at one electrode by the electrolytical decomposition
of a molten halogen salt, and reducing the compound produced by the reaction by the
halogen element liberated at the other electrode, these operations taking place
continuously in the manner set forth.
T: DET ... of Arun 1800
W. Lloyd Wise,
DOUGLAS DIXON.
46, Lincoln's Inn Fields, London, W.C.. Agent for the Applicant.