Improvements relating to the Extraction of Aluminium from its Chlorides and to Apparatus therefor.
Year: 1887

page_text: Date of Application, 3rd Feb., 1887
Specification Accepted, 11th Nov., 1887
[Communicated from abroad by THE COUNT RUDOLPHE DE MONTCELAS, of
Philadelphia, Pennsylvania, United States of America.]
Improvements relating to the Extraction of Aluminium from its
Chlorides and to Apparatus therefor.
I, HENRY HARRIS LAKE, of the firm of Haseltine, Lake & Co., Patent Agents,
Southampton Buildings, in the County of Middlesex, 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 a new simple and cheap process for depositing metallic
aluminium electrolytically from a solution of its chloride. My said process is a con-
tiuuous one, in that it is simply necessary with an anode embodying the compound
hereinafter described to maintain the normal strength of the solution, when a constant
deposition of the metal occurs.
In the accompanying drawings, Fig. 1 is a sectional view showing the arrange-
ment of the galvanic bath for the preparation of my electrolytic solution, and Fig. 2
is a similar view showing the arrangement of the bath for the electro-deposition of the
metal. Similar letters of reference indicate like parts.
A, Fig. 1, is a containing vessel or tank in which is a porous partition B, of
earthenware or other suitable material, whereby the vessel A is divided into two
compartments C and D. In compartment U is an electrode of inetallic aluminium E.
In compartment D is an electrode F, of brass or copper.
I first prepare a suitable quantity of chloride of aluminium—say one gallon-which
I make by dissolving about four pounds of alumina in hydro-chloric acid sufficient to
effect complete solution. I then evaporate said solution at gentle heat to obtain the
dry salt. This salt I re-dissolve in hot water so as once more to produce a gallon
of fluid. This fluid I place in the compartment of the vessel shown in Fig. 1.
The compartment C in said vessel is filled with ordinary chloride of sodium with
sufficient water to make a heavy solution. The electrodes E and F are then connected
in circuit with a battery, being the anode and F the cathode. The solution in
compartment D has normally a yellow color. The current is to be maintained until

page_text: said solution becomes colorless. Said solution is then a solution of the double
chloride of aluminium and sodium, instead of simply a solution of chloride of
aluminium.
The electro-deposition of the metallic aluminium is effected in the vessel A¹ Fig. 2,
which may be in all respects similar to vessel A Fig. 1 and is similarly provided with
a porous partition B¹ and compartments C¹ and D¹. In the compartment C¹ is an
electrode G of carbon; in the compartment D¹ the electrode F¹ may be of brass or
copper.
The colorless solution as above described having been obtained is evaporated to
dryness so as to drive out any excess of acetous matter and render the salt as neutral
as possible. The salt being again dissolved in hot water is placed in the compart-
ment D. The compartment C is filled with what I term my anode compound which
consists of a mixture of chloride of sodium and neutral double chloride of sodium
and aluminium in equal parts fused together to form a cake which is broken into small
fragments. These fragments are placed in the compartments C¹ in contact with the
electrode G.
I now connect the electrodes in circuit, when the deposition of pure metallic
aluminium upon the cathode begins. This deposition as long as the com-
partment is kept supplied with anode compound is continuous; said compound
serves to maintain the electrolytic solution of normal strength.
As soon as the cathode becomes covered with aluminium as thickly as may be
desired, the aluminium may be removed and fused in a crucible under a flux, such as
chloride of potassium, so as to obtain a homogeneous mass of the metal.
Instead of using a carbon anode G surrounded with fragments of my above
described anode composition I may combine the carbon and the anode composition
to form an anode as a single block or mass. To this end I intimately mix together
chloride of sodium, double chloride of aluminium and sodium and ground
coke in the proportions of about fifty per cent. of double chloride and twenty-five
per cent. each of the other ingredients. To this I add a sufficient quantity
of a suitable agglutinating substance, preferably coal tar, to render the whole
mass plastic, when I mould it into the form of a plate under pressure and finally bake
it hard at a temperature of about 250 degrees Fahrenheit. In place of using double
chloride of sodium and aluminium in making this anode, I may employ amorphous
aluminium, that is to say, the gray powder which is a bye-product of the extraction of
metallic aluminium from its chloride when the same is effected by the process
described in the specification of former Letters Patent dated Aug. 18 A.D. 1886
No. 10,606, the said powder being a result of the incomplete reduction of the metal.
With this powder I mix ground coke, coal tar and chloride of sodium as before.
With an anode thus formed it is not necessary to use the fragments of anode com-
position in the compartment (but simply to place the molded anode therein with a
heavy solution of chloride of sodium.
Instead of brass or copper cathode I may use as a cathode a thin plate of pure
aluminium. The electro-deposited aluminium and the cathode plate are then fused
together, the advantage being the saving of the necessity of removing the
aluminium from the plate, which is of course required when said plate is of other
metal.
It is important to observe that the liquid in the bath should be kept neutral and not
acetous.
Having now particularly described and ascertained the nature of the said
invention, and in what manner the same is to be performed, as communicated to
me by my foreign correspondent I declare that what claim I is:—
1. The improvement in the art of electrolytically depositing metallic aluminium,
which consists in subjecting a neutral solution of double chloride of aluminium and
sodium to electrolysis in the presence of an anode containing a conducting body (such
as carbon) and a compound of chloride of sodium and double chloride of sodium and
aluminium.

page_text: 2. The improvement in the art of electrolytically depositing metallic aluminium,
which consists in first preparing a neutral solution of double chloride of sodium and
aluminium from alumina substantially in the manner specified and then depositing the
metallic aluminium from said solution in the presence of an anode containing a con-
ducting body such as carbon and a compound of chloride of sodium and double
chloride of aluminium and sodium.
3. The anode composed of double chloride of aluminium and sodium (or amorphous
gray powder as specified), chloride of sodium, carbon and an agglutinating material
substantially as set forth.
y 1887.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C.,
Agents for the Applicant.