Improvements in the Manufacture or Production of Aluminium.
Year: 1890

page_text: Date of Application, 6th Feb., 1890
Complete Specification Left, 4th Dec., 1890-Accepted, 17th Jan., 1891
PROVISIONAL SPECIFICATION.
Improvements in the Manufacture or Production of Aluminium.
I GEORGE SHENTON of 31 St. Swithin's Lane in the City of London Gentleman do
hereby declare the nature of this invention which has been communicated to me from
abroad by Maurice Jacques Berg of 16 Rue des Filles du Calvaire Paris in the
Republic of France Chemist to be as follows:-
This invention relates to a process for the manufacture of aluminium by the action
of electricity and simultaneously effecting its purification by the presence during the
operation of a suitable quantity of an alkaline nitrate such as nitrate of soda or of
potash the current employed being of low tension and high intensity.
In the presence of a reducing agent such as coke dust which acts at the same time
as a reducing agent and as a conductor for the current substances containing alumina
such as cryolite, bauxite, websterite, sulphate of alumina, crude clay or brick dust,
kaolin emery and the like can be reduced by an electric current of sufficient intensity
without the application of other heat than that produced by the passage of the electric
current. The electro motive force of this current should not be more than fifty volts and
may range between 20 and 50 volts according to the nature of the materials employed.
The following is an example of the way in which this invention may be carried into
practical effect.
A mixture of coke dust or charcoal dust nitrate of soda or potash (sulphide of
potassium or of sodium may be used if desired) and of either or any of the aluminiferous
substances hereinbefore indicated being finely pulverised is placed in a crucible
preferably of plumbago between two carbon electrodes which should be dense and of
good conducting power. Into this mixture there is caused to pass an electric current
of a tension of from 20 to 50 volts and of an intensity of from about 1,000 to 10,000
ampères according to the nature of the materials. employed. The presence of the
carbon dust rendering the charge conductive the aluminiferous substances melt and
metallic aluminium is deposited at the negative pole and remains melted its presence
in the liquid condition acting as an accumulator of heat At the same time the foreign
metals and the silica resulting from the employment of clays and bricks are burned
by the nitrates and disappear in the state of oxides.
The manufacture should be conducted in a continuous manner the aluminium being
removed as fast as it is produced and fresh quantities of aluminiferous materials being
continuously added to the charge.
Vessels composed of lime, magnesia or plumbago should be employed in order to
obtain an aluminium pure or practically pure by obviating the presence of the silica
which is liable to be produced in vessels composed of common fire clay.
Dated this fith day of Feb
1000
J. H. JOHNSON & Co.,
47, Lincoln's Inn Fields, London, W.C., Agents.
COMPLETE SPECIFICATION.
Improvements in the Manufacture or Production of Aluminium.
I GEORGE SHENTON of 31 St. Swithin's Lane in the City of London Gentleman do
hereby declare the nature of this invention (which has been communicated to me
from abroad by Maurice Jacques Berg late of 16 Rue des Filles du Calvaire Paris in
the Republic of France but now of 110 Boulevard des Courcelles Paris aforesaid
Chemist) 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 a process whereby pure metallic aluminium can be directly
and continuously extracted from aluminiferous materials.
According to this invention the aluminiferous matter or materials such as cryolito,
D

page_text: bauxite, websterite, sulphate of alumina, crude clay, brick dust, kaolin, emery and
the like are mixed with carbon and an alkaline nitrate or sulphide or both and
exposed to the action of an electric current of low tension or small electro-inotive
force and of high intensity or great quantity as hereinafter described.
In carrying out this invention in practice the process is conducted as follows:-
A mixture of finely pulverised coke, coal, or carbon, nitrate of sodium or
potassium, sulphide of sodium or potassium and either or any of the aluminiferous
materials such as those herein before mentioned and likewise in a finely pulverised
condition is placed in a crucible or melting chamber preferably of plumbago between
electrodes which if pure aluminium is to be produced should be both of carbon,
dense and of good conducting power.
An electric current of from about 20 to 50 volts
for example and from about 1,000 to 10,000 ampères for example according to the
nature of the materials is then passed through this mixture.
If bronze-aluminium is to be made then the negative electrode will be of copper.
If ferro-aluminium is to be made then the negative electrode will be of iron and so on.
The pulverised carbon renders the charge conductive, the aluminiferous substances
melt and separate from the metallic aluminium which passes to the negative pole;
this aluminium remains liquefied and in this condition acts as a heat regulator or
accumulator. At the same time the foreign metals and the silica which are present
when clay and bricks are employed are burned by the nitrate and sulphide and separate
out in the form of oxides.
The burning or oxidising action of the alkaline nitrate is confined to the iron, silica
and other impurities owing to the peculiar property of metallic aluminium of being
capable of superficial oxidation only even at the temperature of fusion and of not
dissolving the nitric acid whilst the metallic iron becomes converted under the action
of heated nitric acid into oxide or ogygen salts with generation of nitrogen bioxide
and the incandescent silicon is burned into silicic acid or is converted by the alkali
present into a silicic acid salt. The iron oxide and the silicic acid produce the slag
which remains bebind when the pure aluminium is run off..
The oxidising action of the alkaline sulphide is due to the fact that the iron or other
metal associated with the aluminium becomes converted by the sulphur of the alkaline
sulphide into a sulphur compound such as sulphuret of iron for example and in this
form passes into the slag directly or partly after being burned to oxide.
In operating on a larger scale the following is a suitable way of proceeding.
A inelting chamber or receptacle of suitable dimensions is employed preferably of
rectangular form in transverse section and provided with a tapping hole in its
lower part.
This chamber or receptacle is constructed with carbon plates in such a manner that
the chamber constitutes the negative electrode. The positive electrode formed by a
block or rod of carbon is inserted into the mixture and the electric current of the
description herein before stated is passed through the charge.
The mixture and the positive electrode soon become incandescent and the current
should be maintained as constant as possible by means of an Ampère meter.
One of the most important advantages of this process compared to other processes
for obtaining aluminium by means of electricity consists in the addition to the mass
of the alkaline nitrate and alkaline sulphide in addition to the reducing substances
pulverised coal coke or carbon.
The proportions of the alkaline nitrate and alkaline sulphide to be added will vary
with the quantities of aluminiferous material such as cryolite and bauxite employed.
The best results are obtained by adding 2 parts of alkaline nitrate or alkaline sulphide
(nitrate of soda or potash) to 100 parts by weight of bauxite for example but these
100 parts of bauxite must again be in proportion to the cryolite and retort carbon.
For instance I take
Cryolite 90 parts by weight,
Retort carbon 5 parts by weight,
Bauxite 5 parts hy weight

page_text: the mass becomes perfectly liquid. An additional quantity of bauxite is now added
which melts and mixes with the molten cryolite and every 5 or 6 minutes a quantity
of several pounds of bauxite is thus added until about 100 parts by weight of bauxite
have thus been introduced. After the process is well started in operation that is to
say after the bath is thoroughly fluid and incandescent then the 2 parts by weight
of nitrate of soda or potash are added. About 5 or 6 minutes afterwards the tapping
hole is opened and pure aluminium runs out. After all the aluminium has run out
new quantities of bauxite are introduced as before until the proportion of 100 parts
by weight is made up again. 2 parts by weight of the nitrate are then added and so
If the quantities of bauxite and cryolite are greater then the quantities of nitrate
are increased likewise. There are always 2 parts by weight to 100 parts by weight
of bauxite if the quantity of bauxite is smaller then the quantity of nitrate is smaller
in proportion.
on.
:
When other aluminium combinations such for example as emery, brick, clay and
the like are employed in place of bauxite the process is conducted in the same way as
with bauxite.
In case the electric current has not sufficient quantity to effectually melt the
mixture the melting process may be aided by the application of heat from the
combustion of fuel by placing the melting pot or chamber over a fire taking
the precaution to protect it from burning by means of a casing of clay or plumbago.
It is essential in all cases to regulate the process not by ordinary temperature but by
the employment of a current of sufficient intensity or quantity such as from 1500
to 2000 ampères care being taken to use a positive electrode of sufficient area to
admit of the passage of a current of this quantity.
The cryolite may be allowed to remain permanently without renewal. In case a
small quantity of cryolite escapes in drawing off the aluminium, it should be put back
in the melting chamber.
The positive electrode is gradually pushed forward as it burns away and must be
periodically renewed but the receptacle or melting chamber remains in working order
for a relatively long period. This chamber is preferably constructed with independently
renewable plates of carbon placed in a cast iron casing. The process of extracting
the aluminium may thus be worked in a continuous manner the metallic aluminium
being drawn off or removed as fast as it is produced and the melting chamber
continually receiving fresh supplies of aluminiferous materials.
In order to obtain the aluminium in a condition of purity to the extent of about
99 per cent. it is advisable to employ melting chambers or receptacles composed of or
lined with lime, magnesia and graphite in order that the materials may not be .
exposed to contamination with the silica which is present in vessels made of ordinary
fire clay.
An electric current suitable for this process can be conveniently obtained from a
Siemens and Halske dynamo such as is employed in the manufacture of copper and
capable of supplying a current of from about 1000 to 2000 ampères and about 3 volts
or less or from a Crompton dynamo supplying a current of from about 10,000
to 15,000 ampères and from about 40 to 50 volts for example. The conductors and
connections must evidently be of suitable area for conveying the current without
becoming heated and may be arranged in a similar manner to those employed in
electric welding operations.
By the addition of the alkaline nitrate and alkaline sulphide during the melting
process a great advantage is obtained it being thereby rendered possible to obtain pure
aluminium of considerable commercial value from less pure raw materials than have
heretofore been employed or substances containing a relatively large amount of foreign
substances such as unprepared clay or brick dust, substances which owing to the
facility with which they can be generally obtained as refuse or a natural product are
of little value in themselves.
The whole or a considerable portion of the oxide of iron, silicic acid and the like in
the crude clay or raw material being reduced to metallic iron silicon and the like by
the action of the electric current are liable when the process is conducted in the

page_text: manner, heretofore practised to combine with or contaminate the metallic aluminium
but by the action of the alkali ne nitrate these substances are reoxidised and reconverted
into oxide of iron and silicic acid etc. forming part of the slag which remains in the
crucible when the pure aluminium is drawn off.
In this improved process an important advantage is secured by introducing the
alkalinė nitrate directly into the molten mixture of aluminiferous matter with coke or
carbon dust liquified by the action of the electric current in place of adding these
substances after the impure aluminium is formed as is done in other processes thereby
involving a separate operation for the purification.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be perforined, I declare that what I
claim is: :-
1. The manufacture or production of aluminium by electrolysing a mixture of
aluminium yielding compound or substance and a reducing agent in the presence of an
alkaline nitrate substantially as hereinbefore described.
2. The manufacture or production of aluminium by subjecting a mixture of
aluminium yielding compound or substance and a reducing agent to an electric
current in the presence of an alkaline nitrate and of sulphide of an alkali substantially
as herein before described.
3. The manufacture or production of aluminium by subjecting the materials referred
to in either of the preceding claiming clauses to an electric current of low tension or
electro motive force and high intensity or large quantity substantially as hereinbefore
described.
LT
571
1
T
1800