the Electrolytic Freparation of Alum |
Year: 1895

page_text: Date of Application, 28th Mar., 1995-Accepted, 16th Nov.. 1895
the Electrolytic Freparation of Alum
| ALBERT ROGER, Chemist, of 41 Rue Boursault, Paris, in the Republic of
France, 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 :-
According to this invention it is by the electrolytic treatment of a solution
essentially alkaline that chemically pure aluminium is obtained. This solution is
obtained by the ordinary process.
The bauxite used for this solution is as is well known composed of hydrate of
alumina, a small quantity of silicate of alumina, of sesquioxide of iron and a residue
of various substances having no effect on the operation and of which no notice
need be taken.
I take an ebonite vat A (Fig. 1) at the bottom of which there is a mercury
bath B. On this mercury is poured a certain quantity C of the alkaline solution
into which dips a conical body composed of the following substances: Bauxite
finely pulverised and crude petroleum mixed in a suitable proportion to form a
thick paste capable of being rolled and which is then calcined at a high temperature
and in a closed jar.
I have therefore on the one hand the carbon D forming the anode of the
system and on the other hand the mercury B forming the cathode. It only remains
to pass an electric current through C when the following action is produced:-
The aluminate and the silicate of soda are entirely decomposed. The aluminium
is amalgamated with the mercury whilst the soda is carried entirely on the anode,
forming, by reason of the composition of the said anode, aluminate of soda which
regenerates the bath. As regards the silicium it is precipitated in the form of
powder and sometimes of small crystals.
There is also deposited on the mercury carbon dust liberated by the transforma-
tion of the alumina contained in the anode into aluminate of soda.
The amalgam contains aluminium and furthermore about 2 per cent. of sodium
formed during the operation. All the impurities such as carbon silicium etc.
which float on the surface of the amalgam are removed and need not be considered.
The presence of this per cent. of sodium is far from being a disadvantage, it is
even necessary for in casting in iugots this sodium is transformed into soda and
consequently protects the aluminium from oxidising and from dissolving its oxides :
the aluminium will thus be purer more resisting and less attackable by chemical
agents most valuable qualities which it does not possess when obtained by the
methods hitherto employed.
When it is observed that the amalgam contains sufficient aluminium it is taken
out of the vat A and put into chamois leather pockets from which by means of
bydraulic pressure a first excess of mercury is removed. The final distillation
of the mercury then takes place in cast iron retorts by ordinary methods.
It is well to note that all the substances primarily used such as aluminate of
soda mercury and carbonate of soda are recuperated in the course of the various
operations with the minimum of loss.
I now describe the commercial apparatus designed to produce the aluminium, its
theoretical operation having been described above.
The commercial apparatus is composed of a setting in bricks H H H (Figs. 1

page_text: and 2) on which rest a succession of vats A A the number of which is only limited
by the output of the works.
In the axis of each vat, and below, the setting has an arched opening I for the
withdrawal of the amalgam.
The vats A of thick ebonite terminate in conical bottoms allowing the amalgam
to easily flow through a pipe E provided with a stop cock F into cast iron recep-
tacles brought by a waggon K running on a small tramway with turnover points
or necessary turntables.
The vats are bored at G G allowing the passage of a platinum rod provided at
one end with a globe of the same metal dipping into the mercury and joining at
the other end the conducting wires L L of the current. These conducting
wires L L are one the leading in wire and the other (Figs. 1 and 2) the return
wire.
These wires end at plug connection permitting of the use of such number only
of the vats as may be desired.
The carbons D of solid conical shape are in two parts and bored furthermore
centrally with a circular opening for the free passage of the mechanical stirrer.
A bronze crown R the interior surface of which surrounds the outside of the
carbons serves to support the latter and to insure electrical contact. On this
crown are fixed two stops S S each connected by a leading in and return wire to
the bronze plates O and P of the commutator. In this manner the system of
vats are connected in series.
On the crown are screwed four rings connected two by two by means of strong
cords and serving with the windlasses T to lower the carbons proportionately as they
become used or to effect their replacement.
The operating cords U U U run on grooved pulleys V V V mounted on
bearings which are bolted to a strong iron girder X with wide flanges sustained at
intervals by cast iron columns Y the feet of which are set in the masonry.
E' are
AA is a steel shaft supported at its extremities by plummer blocks B₁ and on
which are two pulleys one fast C¹ and one loose D' of the same diameter.
banging plummer blocks supporting the shaft A¹.
GG are bevel gear wheels keyed on the shaft A' and actuating the
wheels H H which set in motion the mechanical stirrers I' the shaft and blades
of which are of lignum vitæ.
Such is the detailed description of the commercial apparatus designed for the
production of aluminium.
my
Having now particularly described and ascertained the nature of said
invention and in what manner the same is to be performed, 1 declare that what I
claim is :-
The simultaneous use of an alkaline liquid as electrolyte, of an aluminous
substance which is a good conductor of electricity (aluminous carbons &c.) as
soluble anodes and of metallic mercury as cathode for the preparation of pure
metallic aluminium by electrolysis.
Dated this 27th day of March 1895.
WHEATLEY & MACKENZIE,
40 Chancery Lane, London, W.C., Agents.