IMPROVEMENTS IN PROCESS OF AND APPARATUS FOR REDUCING METALS BY ELECTROLYSIS
Year: 1884

page_text: We AUGUSTUS JAMES ROGERS Chemist, JULIUS KOEBIG, Chemist and HENRY
MANN, Manufacturer, all of Milwaukee in the County of Milwaukee and State of
Wisconsin, one of the United States of America, do hereby declare the nature
of the Invention for "IMPROVEMENTS IN PROCESS OF AND APPARATUS FOR
REDUCING METALS BY ELECTROLYSIS and in what manner the same is to be
performed, to be particularly described and ascertained in and by the following
statement :-
$1
It has for many years been known that any salt dissolved in water could be
separated into its base and acid constituents by passing an electric current through
the solution, the acid part going to that point where the current enters the solution,
namely the positive electrode, and the base or metal going to that point where the
current leaves the solution, namely the negative electrode.
This principle has been applied to various branches of electro-chemical industry,
such as electro-gilding, electro-plating, electrotyping and so forth. This principle
has also been applied to a very limited extent to the reduction of metals from their
soluble salts, but it has been found applicable only to those metals which are not
acted upon by water and whose salts are soluble in water. No other method of
which we are aware has ever been used for commercially obtaining metals or
metalloids from their compounds by electrolysis.
This process consists in heating the compound (meaning oxide, ore or salt), or a
mixture of compounds, to the point of fusion, in one vessel, and submitting the
electrolyte (so called) thus obtained in an independent vessel to the action of the
electric current. This passing of the electric current through the electrolyte is called
electrolysis. The result of the electrolysis would be that in general, the metal would
go to the negative electrode and the metalloid or acid to the positive electrode.
This method of electrolysis is especially applicable to those elements having
great affinity for oxygen such as sodium, potassium, calcium barium, strontium,
magnesium, aluminium, boron, silicon, phosphorus and so forth, since they take
oxygen readily from water or air hence the electrolysis could not take place in an
aqueous solution of the salt.
In general, it is better to use the binary compounds, such as oxides, chlorides,
bromides iodides, fluorides, sulphides, and so forth, but when a binary salt

page_text: volatilizes easily after reaching the point of fusion, or offers great resistance, to the
electric current, ternary or other compounds may be used. It is also sometimes of
advantage to use a mixture of compounds to increase the conductivity of the
electrolyte, or to lower the point of fusion, for example, the addition of calcium
chloride, to potassium chloride, or to sodium chloride, in equal molecular proportions
lowers the point of fusion of potassium chloride. So also in the electrolysis of
magnesium chloride the addition of potassium chloride and ammonium chloride
lowers the point of fusion.
In the accompanying Drawings, which illustrate a convenient form of apparatus
for carrying out the process, Figure 1 represents a vertical longitudinal section
of the melting pot decomposing tauk and condensing apparatus on the line y-y of
Figure 2 and Figure 2 is a horizontal section of a portion thereof taken on the
linex of Figure 1.
A A¹ represent suitable masonry within the walls of which the apparatus is to
be located and B is a fire-bed, beneath the melting pot C. The latter is preferably
of the shape shown in order that the products of combustion may encompass as
much of its exterior surface as possible. The said pot is provided with a tight
cover removably secured thereto as shown but furnished with a funnel or
hopper c¹ in its center adapted to be closed by a float valve c when it is full, that
is, so arranged that it will receive no further supply of salt, when the liquid
obtained by the melting of that first put into the pot rises as high as the lower
projecting edge of the hopper c' The cover C¹ is further fitted with a safety-
valve c³ to guard against danger from any sudden pressure occasioned by formation
of gas.
D is the decomposing tank, divided into two parts by the partition d of porous
material, such as fire-clay and which extends down to within a short distance of
the bottom of the tank as indicated by the line in Figure 1. E is a pipe
extending from a hole in the center of the bottom of the tank D just beneath the
partition d to a hole in the bottom of the melting pot C and this pipe is provided
with a suitable stop-cock e to govern the passage of the melted material from the
pot to the tank. N and P are respectively negative and positive electrodes placed
within the two sections of the decomposing tank and connected by wires (which
are protected by passing through fire-clay or other tubes n and p against the
corroding action of the electrolyte or its constituents) with the electric generator,
(not shown).
The tank D is furnished with a tight cover D' which is perforated to receive
two goose necks F F¹ (one only, on the negative side being shown in Figure 1 but
the position of both as well as of all the man-holes being represented by dotted
circles in Figure 2) and man holes ff and ff.
The central partition d of the tank D must fit gas-tight, with or against the said
cover so that there may be no communication above the liquid in the tank between
the negative and positive sides thereof, the only communication between the two
divisions of the tank for any free liquid or free gas being therefore by means of the
liquid in the tank at the bottom under the central partition, although the electric
current, as well as the ions of the electrolyte, may pass freely through the partition d
by reason of its porous character.
G is a condenser provided_with a worm G₁ connecting at its upper end with the
small end of the goose-neck F and, at its lower end having an outlet g, guarded by
a cock g' below which is a branched tube, the forks of which lead, into different
receptacles HH' the cock being so constructed as to shut off communication
between the condenser and either or both of said receptacles at will, and the latter
may either be rigidly connected together and to the other portions of the device as
shown, or may be each bodily removable, and they are provided with close fitting
covers, which may also have openings suitably closed, therein if desired.
I is an open-topped tank for containing liquid hydro-carbon as hereinafter
described and h and h¹ are two pipes connecting the said tank with the
receptacles H and H¹ respectively provided with suitable cocks i and ¹. The

page_text: goose-neck F (indicated by dotted lines on the positive side) is not connected with
a condenser ordinarily, but may lead off into any other suitable tank, or receptacle
for the purpose hereinafter explained.
The apparatus, thus described is especially intended for the production of pure
sodium and potassium from their salts and by way of illustration we will describe
its use in the reduction of chloride of sodium.
The salt is poured into the melting pot C (which is preferably of the shape
shown, and may be made of clay, iron or other heat-resisting, non-corrosive
material) through the funnel in the cover and subjected to such a degree of heat as
will keep the contents with the constant new supply of sodium chloride, some
degrees above the point of fusion, say about 500° centigrade. The decomposing
tank D is preferably made of clay, or other similar heat resisting material which
should be non-conducting in the form of apparatus herein illustrated and it should
be protected from loss of heat by conduction or radiation as by walling it in with
the furnace as here shown; the best shape for this tank is that of a rectangular
parallel opiped deep and narrow, and one which is one foot in width, three in
length and four in depth would be of convenient proportions for practical working
purposes. Several tanks of this or other size could be used at one time by being
connected in a series. Within the said tank divided as hereinbefore described are
preferably located the electrodes N and P which are most conveniently carbon-
plates connected by proper wires with the electric generator, which latter may be
a lynamo machine, although the particular kind of generator is not material that
named being the best in ordinary cases, as the greatest amount of electric
power may be most economically obtained thereby. These carbon plates should
present as large a surface as practicable in the electrolyte and should be near
together to decrease the resistance to the passage of the current through the
electrolyte, which latter consists of the melted sodium chloride conveyed into the
decomposing tank through the pipe E.
Into the condenser G cold water is constantly passed through the inlet g which
as it becomes heated passes out through the outlet g and into the open tank I is
poured a quantity of coal-oil or other suitable hydrocarbon in liquid form which
in turn passes through pipes h and h¹ into the receptacles H and H' being
normally at the same height and under the same pressure in all three of the
vessels HH¹ and L
The device being constructed as described and the melting pot supplied, with the
salt and heat sufficient to fuse the same being applied the salt is liquified and run
into the decomposing tank, and the electric circuit closed a current passes from the
positive to the negative electrode decomposing the electrolyte in such passage into
sodium and chlorine, which collect respectively on the negative and positive
electrodes. The temperature is such that the sodium is vaporized and passes up
and out through the goose-neck F and through the worm G₁ into one of the
receptacles H or H₁ (according to the way the cock g¹ is turned) and there falls to
the bottom of said tank being specifically heavier than the coal-oil which latter
prevents any possible contact of the oxygen of the outside air with the sodium
which may be collected in its solid form from the said tank as desired, while the
chlorine is led, in its gaseous condition, up through the other goose neck F¹ into
any suitable receptacle where it may be brought into contact with lime to form a
bleaching powder or otherwise disposed of.
We have shown the electrodes as carbon plates suspended within the divisions of
the decomposing tank but we do not confine ourselves to any exact arrangement
of the apparatus in matters of detail since it is obvious that the process could be
carried out with success with the said apparatus modified in a variety of ways.
For instance one or both of the electrodes might be against the sides of the
tank or indeed (with proper outside insulation) might form the side or sides of the
tank itself or the carbon plates might project downward through the cover of
the tank or be arranged in any suitable way not inconsistent with the carrying out
of the described process.

page_text: At any convenient point in the said apparatus (say the cover of the decomposing.
tank) we propose to place a small pipe K, with suitable cock k the object of which
is to afford means of connection with the flexible tube of an air pump, so as
to exhaust the air from the interior of the decomposing tank prior to the
commencement of operation after which through this same pipe (or from another
point if preferred) hydrogen or other suitable gas is introduced into the upper part
of the negative side of the tank or into its goose neck F so that the passage which
conducts the vaporized sodium (or potassium if that substance is under production)
into the receptacle H or H¹ will be supplied with said gas to prevent contact of
oxygen with the contents of the said passage at the commencement of the process
of operation. The hydrogen gas might be used to force air out from the tank by
reason of its introduction therein under pressure, without first having recourse to
an air pump, and it would be well to maintain communication between the upper
part of the negative side of the decomposing tank, and a reservoir of the said gas
during the entire process, under guard of a safety-valve to guard against danger
from rapid condensation or evolution of sodium vapor.
Having now particularly described and ascertained the nature of the said
Invention and in what manner the same is to be performed we declare that what
we claim is :-
1. In an apparatus for the reduction of metals and metalloids by electrolysis of
their salts or ores in a melted condition, the combination of a melting pot located
over a suitable fire-bed and an independent decomposing tank provided with
electrodes, and a close-fitting cover having gas-tight passages leading therefrom and
a condensing apparatus and receptacles together with suitable connecting pipes and
cocks, all arranged and adapted to operate as set forth.
2. The process of separating sodium or potassium from sodium chloride or
potassium chloride, substantially as described, consisting in heating the salt to the
point of fusion in a suitable vessel, conveying the liquid thus obtained to a separate
independent decomposing tank provided with electrodes, and passing an electric
current through the liquid to separate the chlorine therefrom and then conducting
the gaseous chlorine and vaporized sodium or potassium into separate receptacles,
that for the latter containing coal oil, and the passage which conducts the vaporized
sodium or potassium into the said receptacle being supplied with hydrogen, or other
suitable gas, to prevent contact of oxygen with its contents at the commencement
of the process of separation.
Dated the 4th day of Anvil 1001