Improvements in or relating to the Electrolytical Decomposition of Metallic Salts, and in Apparatus therefor.
Year: 1892

page_text: Date of Application, 2011 Sept. 1005
Complete Specification Left, 11th Oct., 1892-Accepted, 10th Dec.,
1892
PROVISIONAL SPECIFICATION.
Improvements in or relating to the Electrolytical Decomposition of
Metallic Salts, and in Apparatus therefor.
I, CHARLES KELLNER, Doctor of Philosophy, of Wasagasse 39 Vienna 1, Austria,
General Manager of the Kellner-Partington Paper Pulp Co. Ltd. do hereby
declare the nature of this invention to be as follows:-
This invention relates to the use in the electrolytic decomposition of metallic
salts, of a mercury-cathode of novel contruction for the purpose of obtaining
metals in the solid or metallic state, or in the form of hydrates, or other desired
combinations of the same. It also relates to apparatus whereby the use of mercury
for this purpose is rendered practicable for operations on an industrial scale.
Heretofore repeated attempts have been made to employ mercury as a cathode,
but such attempts have not been successful when operating on an industrial scale,
because either the mercury and the metal contained therein remained in constant
contact with the electrolyte, whereby a portion of the amalgam already formed
continually became decomposed again, and reactions were produced that interfered
with the progress of the process, or because the mercury had to be employed as a
"flowing cathode over metal plates and the like, and this operation required too
large a quantity of this expensive metal, and resulted in loss of the same. More-
over the requisite apparatus has been hitherto too expensive as well as unsuitable,
in consequence of its complicated construction, for industrial purposes.
In order to obviate these drawbacks, there is employed according to the present
invention, as the cathode, a thin vertical layer of mercury which is separated
from the anode space containing the solution of the electrolyte by partition walls
that conduct the current, the metal separated being removed immediately after its
formation either in a mechanical manner or in an electrical manner from the
sphere of action of the remaining electrolyte to be decomposed.
or
This separation is effected in a mechanical manner, according as the metals are
to be obtained from the salts treated, in the form of hydrates, or in the metallic
state, or as solutions of any desired salts by causing respectively water;
mercury or an acid or other body that is to be united or combined with the
cation, or is intended to carry away the cation, to flow through the cathode spaces
during the electrolytical process, whilst the separated anion is drawn off from the
anode spaces or is allowed to escape freely therefrom.
The mercury employed as a cathode is in the form of a vertical thin layer and
acts in this case as an intermediary between the electrolyte (which is separated
therefrom by the partition wall) and the water, or mercury, or acid or other body
flowing in contact therewith, because it takes up through the partition wall in a
metallic state the metal separated as a cation, and constantly gives it up to the
water or to the other body employed in place thereof according to the product
required as above explained. When water employed, it forms a hydrate with
the metal, with the evolution of hydrogen and generation of heat, whilst when
mercury is employed, an amalgam with the metal is produced, from which the
latter can be separated in a metallic state, it may be by a second electrolysis.
When an acid or other solution is used to combine with the cation, there is
obtained a solution of the corresponding salt.

page_text: The separated metal can be removed in an electrical manner from the scope of
action of the electrolyte to be decomposed, by employing as the anode of a second
cell the metal which separates at the mercury cathode, the said second cell being
arranged in the decomposing cell and its cathode being electrically connected with
the mercury.
In this manner the metal is constantly removed from the decomposing cell and
causes the formation of the desired compounds in the secondary cell to take place
separately from the decomposition of the metallic salt in the decomposing cell.
Furthermore diffusion of the two liquid conductors cannot take place through the
mercury electrode.
The formation of the metallic compound in the secondary cell however takes
place on short-circuiting the same, much more quickly than the separation of the
metal at the mercury cathode, so that the secondary cell never reaches its full
electro motive force. For this reason the secondary cell need not be short-
circuited, but may serve to perform work to an extent such as will not inter-
fere with the rapid removal of the metal from the mercury electrode.
When the cell is short-circuited, in which case the conversion of the separated
metal into its compounds will take place violently immediately after its formation,
the electrical energy of the secondary cell is employed only to heat the electrolyte
in the cell, whilst a part of the energy can be employed in the performance of
external work.
By including the secondary cells in the circuit of the source of electricity as for
example a dynamo, it is possible to employ a weaker main current, or a weaker
machine, because the current generated in the secondary elements flows in the
same direction as the main current and therefore strengthens the latter.
Since the mercury is employed in each case only in the form of a thin layer,
and is not agitated but remains quiet and is constantly covered with liquid, loss
thereof is prevented.
In this way all the disadvantages which have heretofore attended the direct
decomposition of metallic chlorides are completely obviated, and this invention
renders possible to manufacture for example alkaline hydrates of a greater degree
of concentration and of greater purity than has heretofore been possible.
Although this invention may be carried out with apparatus of various kinds,
I shall now proceed to describe two forms of apparatus which have been proved
to be specially advantageous for the manufacture of caustic soda on a commercial
scale, and which have been found to be very durable.
The somewhat greater internal resistance of this apparatus to the passage of
the current, is more than compensated for by the very small cost of maintenance
and the continuity of working.
In the accompanying drawings,
Fig. 1 is a vertical section through one of the cathodes, of one form of apparatus
according to this invention.
Figs. 2, 3 and 4 show respectively in longitudinal section, sectional plan, and
cross section, another construction of apparatus suitable for working on a com-
mercial scale, and wherein the metal separated at the mercury cathode is removed
mechanically.
Figs. 5 and 6 are sectional views at right angles to each other showing a detail
of such apparatus.
Figs. to 10 inclusive show several arrangements of apparatus in which the
complete decomposition of a metallic salt is effected by using a secondary cell.
Referring to Fig. 1, A, A' are partitions or walls that serve to hold in place the
mercury forming the cathode and separate it from the anode space. These walls
consist of suitable porous or absorbent material such as clay, asbestos-board
saturated with gelatinous material and arranged on a perforated plate of slate; or
of two alternately perforated plates of slate with an intermediate layer of glass
wool, slag wool, carbon or starch (for the purpose of preventing the passage of
electrolyte), the starch being mixed with concentrated solution of soda or with

page_text: boiling water before being inserted in place, in order to form it into paste. These
walls may however be made of leather or of any other desired material that will
allow of the passage of the current and of the ions.
Between these walls, which may if required be provided with a special foundation
and bracing or stiffening for the purpose of resisting the pressure of the mercury
there is situated the mercury B B. In order that as little as possible of this
expensive metal may be used, whilst providing a cathode space of convenient and
cheap construction, there is employed a displacing body C which is preferably
made of cast iron made hollow and filled with lead. This displacing body serves
to nearly fill the space between the walls A, A¹ so as to allow the mercury to
form only a very thin layer at each side.
At ine same time this displacing body C serves as a support to which a vessel D
(hereinafter called the reaction vessel) can be fixed at a certain height by any
suitable means such as the set screw E.
The reaction vessel D, which is open at the bottom, or at both top and bottom,
and almost touches the inner side of the walls A A' forming the cathode space,
dips into the mercury BB' the depth of immersion being capable of adjustment
by means of the screw E. Into the interior F of this vessel D), water, or the
liquid with which the separated cation is to be combined is caused to flow. It is
advantageous to connect together a number of such reaction vessels by means of
overflow channels, so that the liquid flows through the several vessels in succes-
sion in order to pass out sufficiently concentrated.
The mercury B B is connected with the negative pole of an electric generator
either directly by means of a wire, or, as shown in Fig. 1 indirectly by means
of the displacing body C.
The anodes H H may be made of any desired conductor capable of resisting
the chemical action of the liberated anion, for instance of carbon, crude cast iron,
or phosphorus lead, or of lead or platinum coated with carbon. These anodes are
carried by bell shaped supports JJ which serve to conduct the liberated gas to
pipes NN whence it flows to any desired place for use.
The formation of a thin layer or layers of mercury in the cathode chamber can
also be effected in a simple manner without using the displacing body C, by
employing instead of the partition walls A A', plates which are made by inserting
thin rods, wires or strips of sheet metal arranged parallel and near to one
another, into a mixture of cement and water glass, or of cement, powdered glass,
powdered fire clay and water glass, and then when the mixture has set, removing
the said rods, wires, or strips.
The spaces or chambers thus formed are filled with mercury, the columns of
which are electrically connected together by causing the metal to extend to a
height above the upper ends of the intermediate walls forming the said spaces or
chambers.
The comb-shaped mercury cathode thus constructed presents a large surface
with a comparatively small quantity of mercury whilst the plates which serve
to hold the cathode in place have considerable strength and durability.
Each of these cathode chambers is formed at its upper end with a trough-like
enlargement for the reception of the water or of the liquid with which the cation
separated at the mercury cathode is to be combined.
An apparatus furnished with comb-like mercury cathodes of this kind and
which is very suitable for manufacture on a commercial scale, is illustrated in
Figs. 2, 3 and 4.
The apparatus consists of a wooden trough L which is lined with material that
is not attacked by chlorine such for example as paraffined linen on a layer of
resin and tar boiled in linseed oil. This trough is provided at its outer edge
with a circumferential groove / in which is placed an acid proof cement, prefer-
ably of heavy spar with water, or clay such as china carth, with a heavy hydro-
carbon as for example such as is obtained as a residue in the refining of petroleum.
Into this groove is inserted the bent over edge of the cover L which consists

page_text: of a wooden plate having a leaden plate attached to its underside and whereby
a perfectly gas tight joint is effected. Both the wooden plate and the leaden
plate of the cover L' are formed with slots and respectively, the latter 73
being narrower than the former 2. These slots serve for the reception of the
electrodes H and B, and are after the insertion of the electrodes closed gas tight
by filling up the remaining space in the upper slots with the aforesaid cement.
The anodes H are, for the purpose of making contact with the parts thereof
which project above the cover L, each formed with a small trough h (as shown
on a larger scale in Figs. 5 and 6) into which projects a wire that serves to
form an electrical connection with an electric generator. Each trough con-
tains mercury which is covered with a layer of oil.
The cathode chambers B consist of hollow plates A cach of which is widened
out at the top after the manner of a trough to form a reaction space or vessel D
and each of which plates is formed in the manner hereinbefore described with
hollow spaces a arranged after the manner of a comb for the reception of the
mercury. The reaction vessels D) of these cathodes are connected together by
overflow channels M.
This arrangement of apparatus, which is very cheap to construct, allows of the
removal of each electrode separately from the apparatus during working for the
purpose of inspection or renewal.
The electrolyte enters through pipe S and flows in the direction of the arrows
through the zig-zag spaces or channels formed between the anodes and cathodes,
in order to leave the apparatus through the pipe t, and if required to flow into
another apparatus.
The operation of the apparatus is as follows:-
The electrolyte, it may be for instance common salt, enters at S and takes a
zig-zag course through the apparatus, gives up its chlorine at the anodes B from
which it is conveyed away through the pipe Q. The sodium travels through the
walls or sides of the cathode chamber to the mercury cathode and forms there-
with an amalgam which is converted by the water Howing above the mercury
in the reaction vessel D), into caustic soda, and passes through the chamber
into the next reaction vessel and finally passes out through the pipe M as a
highly concentrated solution and in an almost chemically pure state.
In this manner the path to be traversed by the liquid in the reaction vessels.
may be further lengthened by means of partitions suspended in the reaction
vessels D, so as to thereby hasten the enriching of the solution.
By this means solutions rich in caustic soda can be produced the evaporation
of which will therefore necessitate but small cost.
If the reaction vessels are made tight, and if mercury be employed instead of
water, sodium, potassium or other metals can be obtained in a metallic state in
the form of amalgams. Also solutions of any desired salts can be produced by
allowing instead of water, an acid or that body which is to be combined with the
cation, to circulate through the reaction vessels.
Figs. 7 to 10 inclusive illustrate a number of modified constructions of the
second type of apparatus for the complete decomposition of metallic salts it may
be for example an alkaline salt in which a secondary cell is connected to the
decomposing cell which for distinction is hereinafter called the primary cell.
As illustrated, a vessel L is divided by a layer of mercury B into two parts,
which can only communicate electrically with each other through this layer of
mercury. This can be effected for instance as shown in Fig. 7 by cementing
into the vessel L a clay cell A having a very narrow lit-shaped interior filled
with mercury, the arrangement being such as to prevent mingling of the two
liquids at opposite sides of the cell.
These liquids are the solution of common salt which is placed into one com-
partment serving as the primary cell, and water which is placed in the other
compartment serving as the secondary cell. The water may be mixed with
sodium hydrate for the purpose of increasing its conductivity.

page_text: The main current from the dynamo or other source of electricity passes into the
solution of common salt through a carbon-electrode H provided with a bell J for
carrying off chlorine, and passes out again through a wire G immersed in the
mercury cathode B. Into the dilute solution of soda in the secondary cell dips an
electrode I which is connected by a bent piece with the mercury. The mercury or
the metal (sodium) separated thereon and amalgamating therewith, thus constantly
forms with this third electrode I and with the intermediate soda solution, a short
circuited element.
If now a current be sent through the solution of common salt, chlorine will be
separated at the anode H, and sodium at the cathode B. the sodium becoming
amalgamated with the mercury. This amalgam is at the same time the anode of
the secondary cell in which, since it is short-circuited, water is decomposed and a
violent formation of sodium hydrate takes place with generation of heat, whereby
the sodium separated from the solution of common salt is at once withdrawn from
the sphere of action of the primary cell, and an electric current set up in the
secondary cell. Consequently since diffusion between the two cells is impossible.
the decomposition of common salt in the primary cell will continue to take place
without interruption, whilst the solution of sodium hydrate in the secondary cell
continues to become richer. The mercury thus constitutes the cathode for the
primary cell, and also at the same time the anode for the secondary cell.
The apparatus may also be so arranged, as shown in Fig. 8 that the water floats
on the mercury in which case the clay cell A is enlarged at the top so as to
receive the third electrode I, and the water necessary for decomposing the
amalgam.
The layer of mercury B may also be arranged horizontally as shown in Fig. 9.
or obliquely as shown in Fig. 10, whereby the rising of the specifically lighter
sodium-amalgam along the surface of the mercury wetted by the soda solution, is
facilitated, but the apparatus is rendered more complicated.
As already stated the secondary cell instead of being arranged in a short-circuit
to the primary cell as shown, may be arranged in circuit with an electric con-
ductor so that its excess of electrical energy can be utilised in the performance of
external work. Or the secondary cells may be included directly in the main
circuit of the electric generator so that the current from such generator will be
caused to enter the primary cell by the carbon anodes H and to pass out by the
cathodes I of the secondary elements in which case the connections with the
mercury are dispensed with.
The operation herein before described for decomposing common salt and form-
ing sodium hydrate, can be employed in exactly the same manner for decomposing
other compounds whose metallic constituents form amalgams with mercury; the
metallic compounds appearing as final products in the secondary cell being deter-
mined by the nature of the electrolytes in the secondary cell.
In carrying out the above described process, a main difficulty is the construc-
tion of a coherent layer of mercury of extreme thinness, because suitable cells
of the requisite size, thinness and durability can only be constructed with
difficulty.
These difficulties can however be obviated in the following ways.
1. By making a plate of a mixture of cement, powdered fireclay, and water
glass, upon which plate (after slightly setting) there is placed a layer of preci-
pitated chalk of a thickness equal to that of the layer of mercury which it is
desired to obtain and in such a manner that it covers the plate underneath it only
to an extent equal to the desired width of the layer of mercury and the whole is
then covered with a layer of cement, powdered fireclay and water glass, and is
left to harden for a few days. The plate thus produced is then placed in dilute
hydrochloric acid which dissolves out the chalk and thus forms a thin slot or
slit for the reception of the mercury. The water glass cement may have imparted
to it any desired degree of porousness by mixing cellulose therewith.
2. By dipping a woven metallic fabric (metallic cloth) first into nitrate of

page_text: mercury and then into metallic mercury, and placing the metallic cloth so covered
upon the plate prepared according to 1, and then placing a second layer of the
mixture of cement, powdered fireclay and water glass thereon, and allowing the
same to harden. Or a clay cell can be covered with an amalgamated metallic
cloth prepared as described, and then a cement covering applied over all.
3. By silvering an asbestos plate on one side by a chemical process, as for
example by Liebig's method, and applying to the said surface mercury which
forins an amalgam with the silver, and in flowing forms a coherent thin layer.
Two asbestos plates thus prepared are placed with their amalgamated sides upon
each other, and after squeezing out the mercury in excess, are united together.
In either of these ways there is formed an unbreakable, flexible diaphragm with
a very thin internal layer of mercury which can be quickly traversed by the
sodium. The diaphragms are fixed or clamped in frames and are fitted to suit the
cells.
In lieu of the asbestos plates there may be employed any desired woven fabric
having sufficient strength and chemical resisting power, as for example glass-wool.
Also a fabric can in its entirety be silvered, amalgamated and pressed between
asbestos plates. Silver need not be exclusively used to form an amalgam, but
any other metal may be employed which is neutral in a chemical sense towards
the electrolytes of the primary and secondary cells. Such diaphragms with a
thin layer of mercury can be most simply prepared by providing the plates or
fabrics with a coating of mercury amalgam according to the method well known
in the manufacture of mirrors.
Dated this 26th day of Santenber 1892
C. KELLER,
By L. W., per F, B,
Improvements in or relating to the Electrolytical Decomposition of
Metallic Salts, and in Apparatus therefor.
I, CHARLES RELINER. Doctor of Philosophy, of Wasgasse 39 Vienna I, Austria,
General Manager of the Kellner-Partington Paper Pulp Co. Ltd., 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:
This invention relates to a process for the electrolytic decomposition of metallic
salts in carrying out which process use is made of a mercury-cathode of novel
construction for the purpose of obtaining metals in the solid or metallic state, or
in the form of hydrates, or other desired combinations of the same. It also relates
to apparatus whereby this process is rendered practicable for operations on an
industrial scale.
Heretofore repeated attempts have been made to employ mercury as a cathode,
but such attempts have not been successful when operating on an industrial scale,
because either the mercury and the metal contained therein remained in con-
stant contact with the electrolyte, whereby a portion of the amalgam already
formed continually became decomposed again and combinations were produced
that interfered with the progress of the process, or because the mercury had to be
employed as a flowing" cathode over metal plates and the like, and this opera-
tion required too large a quantity of this expensive metal, and resulted in loss of
the same.
Moreover the requisite apparatus has been hitherto too expensive as
66

page_text: well as unsuitable, in consequence of its complicated construction, for industrial
purposes.
In order to obviate these drawbacks, there is employed according to the present
invention, as the cathode, a thin layer of mercury which is separated from the
anode space containing the solution of the electrolyte by partition walls that
conduct the current, the metal separated being removed immediately after the
formation either in a mechanical manner, or in an electrical manner, from the
sphere of action of the remaining metallic salt (electrolyte) to be decomposed.
This separation is effected in a mechanical manner, according as the metals are
to be obtained from the salts treated, in the form of hydrates, or in the metallic
state, or as solutions of any desired salts by causing respectively, water, or mercury,
or an acid or other body that is to be united or combined with the cation, or is
intended to carry away the cation, to flow through the cathode spaces during the
electrolytical process, whilst the separated anion is drawn off from the anode
spaces, or is allowed to escape freely therefrom.
The mercury employed as a cathode is in the form of a thin layer and acts in
this case as an intermediary between the electrolyte (which is separated there-
from by the partition wall) and the water or mercury, or acid or other body flow-
ing in contact therewith, because it takes up through the partition wall in a
metallic state the metal separated as a cation, and constantly gives it up to the
water or to the other body employed in place thereof, according to the product
required as above explained. When water is employed, it forms a hydrate with
the metal, with the evolution of hydrogen and generation of heat; whilst when
mercury is employed, an amalgam with the metal is produced, from which the
latter can be separated in a metallic state, it may be by a second electrolysis.
When an acid or other solution is used to combine with the cation, there is
obtained a solution of the corresponding salt.
The separated metal can be removed in an electrical manner from the
scope of
action of the electrolyte to be decomposed, by employing as the anode of a second
cell (hereinafter called the secondary cell) the metal which separates at the mer-
cury cathode, the said second cell being attached to the decomposing cell and
its cathode being electrically connected with the mercury.
In this manner the metal is constantly removed from the decomposing cell and
causes the formation of the desired compounds in the secondary cell to take place
separately from the decomposition of the metallic salt in the decomposing cell.
Furthermore diffusion of the two liquid conductors cannot take place through
the mercury electrode.
The formation of the metallic compound in the secondary cell however takes
place on short-circuiting the same, much more quickly than the separation of
the metal at the mercury cathode, so that the secondary cell never reaches its
full electro motive force. For this reason the secondary cell need not be short-
circuited, but may be arranged to perform work to an extent such as will not
interfere with the rapid removal of the metal from the mercury electrode.
When the cell is short-circuited, in which case the conversion of the separated
metal into its compounds will take place violently immediately after its forma-
tion, the electrical energy of the secondary cell will be employed only to heat
the electrolyte in the cell, whilst a part of the energy can be employed in the
performance of external work.
By including the secondary cells in the circuit of the source of electricity as
for example a dynamo, it is possible to employ a weaker main current, or a
weaker machine, because the current generated in the secondary cells flows in
the same direction as the main current and therefore strengthens the latter.
Since the mercury is employed in each case only in the form of a thin layer
and is not agitated but remains quiet and is constantly covered with liquid, loss
thereof is prevented.
In this way all the disadvantages which have hertofore attended the direct
decomposition of metallic chlorides are completely obviated, and this invention

page_text: renders it possible to manufacture for example alkaline hydrates of a greater
degree of concentration and of greater purity than has heretofore been possible.
Although this invention may be carried out with apparatus of various kinds,
I shall now proceed to describe two forms of apparatus which have been proved
to be specially advantageous for the manufacture of caustic soda on a commercial
scale, and which have been found to be very durable.
The somewhat greater internal resistance of this apparatus to the passage of
the current, is more than compensated for by the very small cost of maintenance
and the continuity of working.
In the drawings filed with my Provisional Specification,
Fig. 1 is a vertical section through one of the cathodes, of one form of apparatus
according to this invention.
Figs. 3 and 4 show respectively in longitudinal section, sectional plan, and
cross section, another construction of apparatus suitable for working on a com-
mercial scale, and wherein the metal separated at the mercury cathode is removed
mechanically.
Figs. 5 and 6 are sectional views at right angles to each other showing a detail
of such apparatus.
Figs. to 10 inclusive show several arrangements of apparatus in which the
complete decomposition of a metalle salt is effected by using a secondary cell.
Referring to Fig. 1A, A are partitions or walls that serve to hold in place
the mercury forming the cathode and to separate it from the anode space. These
walls consist of suitable porous or absorbent material such as clay; asbestos-
board saturated with gelatinous material and arranged on a perforated plate of
slate or of two alternately perforated plates of slate with an intermediate layer
o glass wool, slag wool, carbon and starch (for the purpose of preventing the
mingling of the two electrolytes), the starch being mixed with concentrated
solution of soda, or with boiling water, before being inserted in place, in order
to form it into a paste. These walls may however be made of leather or of any
other desired material that will allow of the passage of the current and of the ions.
Between these walls, which may if required be provided with a bracing
stiffening for the purpose of resisting the pressure of the mercury, there is situated
the mercury B B In order that as little as possible of this expensive metal may
we used, whilst providing a cathode space of convenient and cheap construction,
there is employed a displacing body C which is preferably made of cast iron made
hollow and filled with lead. This displacing body serves to nearly fill the space
between the walls A. A¹ so as to allow the mercury to form only a very thin layer
at each side.
or
At the same time this displacing body C serves as a support to which a vessel 1)
(hereinafter called the reaction vessel) can be fixed at a certain height, by any
suitable means such as the set screw E.
The reaction vessel D, which is open at the bottom, or at both top and bottom.
and almost touches the inner side of the walls A A forming the cathode space,
dips into the mercury B B', the depth of immersion being capable of adjustment
by means of the screw E. Into the interior F of this vessel I), water, or the
liquid with which the separated cation is to be combined is caused to flow. It is
advantageous to connect together a number of such reaction vessels by means of
overflow channels, so that the liquid flows through the several vessels in succession
in order to pass out sufficiently concentrated.
The mercury B 131 is connected with the negative pole of an electric generator
either directly by means of a wire, or, as shown in Fig. 1 indirectly by means of
the displacing body C.
The anodes H H may be made of any desired conductor capable of resisting
the chemical action of the liberated anion, for instance of carbon, crude cast iron,
or phosphate of lead, or of lead or platinum coated with carbon. These anodes
are carried by bell shaped supports J J₁ which serve to conduct the liberated gas
to pipes N N whence it flows to any desired place for use.

page_text: The formation of a thin layer or layers of mercury in the cathode chamber
can also be effected in a simple manner without using the displacing body U,
by employing instead of the partition walls A A', plates which are made by insert-
ing thin rous, wires or strips of sheet metal arranged parallel and near to one
another, into a mixture of cement and water glass, or of cement, powdered glass,
powdered fireclay and water glass, and then when the mixture has set, removing
the said rods, wires, or strips.
The spaces or chambers thus formed are filled with mercury, the columns of
which are electrically connected together by causing the metal to extend to a
height above the upper end of the intermediate wails torming the said spaces
or chambers.
The comb shaped mercury cathode thus constructed presents a large surface
with a comparatively small quantity of mercury, whilst the lateral plates which
serve to hoid the cathode in place have considerable strength and durability.
Each of these cathode chambers is formed at its upper end with a trough-like
enlargement for the reception of the water or other liquid with which the cation
separated at the mercury cathode is to be combined.
An apparatus furnished with comb-like mercury cathodes of this kind and
which is very suitable for manufacture on a commercial scale, is illustrated in
Figs. 2, 3 and 4.
ihe apparatus consists of a wooden trough L which is lined with material that
not attached by chiorine, such for example as paramned linen, on a layer of
resin and tar boiled in linseed oil. This trough is provided at its outer edge
with a circumferential groove in which is placed an acid proof cement, prefer-
ably of heavy spar with water; or clay such as china earth, with a heavy hydro-
carbon as for example such as is obtained as a residue in the refining of petro-
leum. Into this groove is inserted the bent over edge of a leaden plate
attached to the underside of the cover L which consists of a wooden plate; by
this arrangement a perfectly gas tight joint is effected. Both the wooden plate
and the leaden plate of the cover L, are formed with slots and respectively,
the latter being narrower than the former 12. These slots serve for the recep-
tion of the electrodes H and B, and are after the insertion of the electrodes, closed
gas tight by filling up the remaining space in the upper slots with the aforesaid
cement.
The anodes H are, for the purpose of making electric contact, each provided at
the parts thereof which project above the cover L, with a small trough h (as
shown on a larger scale in Figs. 5 and 6) into which projects a wire h¹ that serves
to form an electrical connection with an electric generator. Each trough h con-
tains mercury which is covered with a layer of oil.
The cathodes B consist of hollow plates A each of which is widened out at the
top after the manner of a trough to form a reaction space or vessel 1) and each
of which plates is formed in the manner herein before described with hollow
spaces a (Fig. 4) arranged after the manner of a comb for the reception of the
mercury. The reaction vessels 1) of these cathodes are connected together by
overflow channels M.
This arrangement of apparatus, which is very cheap to construct, allows of the
removal of each electrode separately from the apparatus during working for
the purpose of inspection or renewal.
The electrolyte enters through pipe S and flows in the direction of the arrows
through the zig-zag spaces or channels formed between the anodes and cathodes,
in order to leave the apparatus through the pipe T, and if required to flow into
another apparatus.
The operation of the apparatus is as follows:-
The electrolyte, it may be for instance common salt, enters at S and takes a
zig-zag course through the apparatus, wherein it is decomposed its chlorine being
liberated at the anodes H whence it is conveyed away through the pipe Q. The

page_text: sodium travels through the plate-shaped walls or sides A of the cathode to the
mercury and forms therewith an amalgam which is converted by the water flow-
ing above the mercury in the reaction vessels D, into caustic soda, which passes
through the overflow channel M into the next reaction vessel and finally passes
out through the pipe M as a highly concentrated solution and in an almost
chemically pure state.
In this manner the path to be traversed by the liquid in the reaction vessels,
may be further lengthened by means of partitions suspended in the reaction
vessels D, so as to thereby hasten the enriching of the solution. By this means
solutions rich in caustic soda can be produced, the evaporation of which will
therefore necessitate but small cost.
If the reaction vessels are made tight, and if mercury be circulated through
them instead of water, then sodium, potassium or other metals can be obtained
in a metallic state in the form of an amalgam. Also solutions of any desired
salts can be produced by allowing instead of water, an acid or that body which
is to be combined with the cation, to circulate through the reaction vessels.
Figs. 7 to 10 inclusive illustrate a number of modified constructions of the
second type of apparatus for the complete decomposition of metallic salts, it may
be for example an alkaline salt, in which a secondary cell is connected to the
decomposing cell, which for distinction, is hereinafter called the primary cell.
As illustrated, a vessel L is divided by a layer of mercury B into two parts,
which can only communicate electrically with each other through this layer of
mercury. This can be effected for instance as shown in Fig. 7, by cementing into
the vessel L, a clay cell A having a very narrow slit-shaped interior filled with
mercury, the arrangement being such as to prevent mingling of the two liquids
at the opposite sides of the cell.
These liquids are the solution of common salt which is placed in one compart-
ment serving as the primary cell, and water which is placed in the other com-
partment serving as the secondary cell. The water may be mixed with sodium
hydrate for the purpose of increasing its conductivity at starting.
The main current from the dynamo or other source of electricity passes into
the solution of common salt through a carbon-electrode H provided with a bell J
for carrying off chlorine, and passes out again through a wire G immersed in
the mercury B. Into the dilute solution of soda in the secondary cell dips an
electrode 1 which is connected by a bent conductor with the mercury. The
mercury, or the metal (sodium) separated thereon and amalgamating therewith,
thus constantly forms with this third electrode I and with the intermediate soda
solution, a short circuited element.,
If now a current be sent through the solution of common salt, chlorine will be
separated at the anode H, and sodium at the cathode B, the sodium becoming
absorbed by and amalgamated with the mercury. This amalgam is at the same
time the anode of the secondary cell in which, since it is short-circuited, water is
decomposed and a violent formation of sodium hydrate takes place with generation
of heat, whereby the sodium separated from the solution of common salt is at once
withdrawn from the sphere of action of the primary cell, and an electric current
set up in the secondary cell. Consequently since diffusion between the two cells
is impossible, the decomposition of common salt in the primary cell will continue
to take place without interruption, whilst the solution of sodium hydrate in the
secondary cell continues to become richer. The mercury thus constitutes the
cathode for the primary cell, and also at the same time the anode for the secondary
cell.
4
The apparatus may also be so arranged, as shown in Fig. 8, that the water
floats on the mercury in which case the clay cell A is enlarged at the top so as
to receive the third electrode I, and the water necessary for decomposing the
amalgam. In this case the electrode I is connected to the mercury below by 5
an insulated conductor as shown.

page_text: The layer of mercury B may also be arranged horizontally as shown in Fig. 9,
or obliquely as shown in Fig. 10, whereby the rising of the specifically lighter
sodium-amalgam along the surface of the mercury wetted by the soda solution,
is facilitated, but the apparatus is rendered more complicated.
As already stated the secondary cell instead of being attached in a short-
circuit to the primary cell as shown, may be arranged in circuit with an electric
conductor so that its excess of electrical energy can be utilised in the perfor-
mance of external work. Or the secondary cells may be included directly in
the main circuit of the electric generator so that the current from such generator
will be caused to enter the primary cell by the carbon anodes H and to pass
out by the cathodes I of the secondary elements in which case the connections
with the mercury are dispensed with.
The operation herein before described for decomposing common salt and form-
ing sodium hydrate can be employed in exactly the same manner for decompos-
ing other compounds whose metallic constituents form amalgams with mercury,
the metallic compounds appearing as final products in the secondary cell being
determined by the nature of the electrolytes in the secondary cell.
In carrying out the above described process, a main difficulty is the con-
struction of a coherent layer of mercury of extreme thinness, because suitable
cells of the requisite size, thinness and durability can only be constructed with
difficulty.
These difficulties can however be obviated in the following ways.
1. By making a plate of a mixture of cement, powdered fireclay, and water
glass, upon which plate (after slightly setting) there is placed a layer of precipi-
tated chalk of a thickness equal to that of the layer of mercury which it is desired
to obtain, and in such a manner that it covers the plate underneath it only to an
extent equal to the desired width of the layer of mercury after which the whole is
then covered with a layer of cement, powdered fireclay and water glass, and is
left to harden for a few days. The plate thus produced in then placed in dilute
hydro-chloric acid which dissolves out the chalk and thus forms a thin slot or slit
for the reception of the mercury. The water glass cement may have imparted to
it any desired degree of porousness by mixing cellulose therewith.
2. By dipping a woven metallic fabric (metallic cloth) first into nitrate of
mercury and then into metallic mercury, and placing the metallic cloth so covered,
upon the plate prepared according to 1 and then placing a second layer of the
mixture of cement, powdered fireclay and water glass thereon, and allowing the
same to harden. Or a clay cell can be covered with an amalgamated metallic
cloth prepared as described, and then a cement covering applied over all
3. By silvering an asbestos plate on one side by a chemical process as for
example by Liebig's method and applying to the said surface mercury which forms
an amalgam with the silver, and in expanding forms a coherent thin layer. Two
asbestos plates thus prepared are placed with their amalgamated sides upon each
other, and after squeezing out the mercury in excess, are united together.
In either of these ways there is formed an unbreakable, flexible diaphragm with
a very thin internal layer of mercury which can be quickly traversed by the
sodium. Such diaphragms are fixed or clamped in frames and are fitted to suit
the cells.
In lieu of the asbestos plates, there may be employed any desired woven fabric
having sufficient strength and chemical resisting power, as for example glass wool.
Also à fabric can in its entirety be silvered, amalgamated and pressed between
asbestos plates. Silver need not be exclusively used to form an amalgam, but any
other metal may be employed which is neutral in a chemical sense towards the
electrolytes of the primary and secondary cells. Such diaphragms with a thin
layer of mercury can be most simply prepared by providing the plates or fabrics
with a coating of mercury amalgam according to the method well known in the
manufacture of mirrors.

page_text: Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed I declare that what
I claim is
1. In apparatus for the electrolytical decomposition of metallic salts, a cathode
consisting of a quiescent layer of mercury arranged between partition walls A A¹
of material that will allow of the travelling of the ions and which separate the
cathode space from the anode space substantially as and for the purpose
described.
2. In electrolytical decomposing apparatus constructed with a mercury cathode
of the kind specified in the preceding claim, a displacing body C adapted to nearly
fill the space between the partition walls and cause the mercury constituting the
mercury cathode to form a thin layer substantially as described.
3. For the formation of a mercury cathode of the kind referred to in Claim 1,
a cathode chamber A made of porous material and formed with a number of narrow
or slit-shaped spaces such as a for the production of thin layers of mercury
substantially as described.
4. In the electrolytical decomposing apparatus having a mercury cathode of the
kind specified in Claim 1 causing the cation to be evolved at a cathode composed
of mercury and obtaining it in the form of a hydrate, or an amalgam, or a salt, by
causing water or mercury, or an acid or other body according to the product
desired, to flow over the mercury cathode, or over a number of such cathodes in
succession substantially as herein described.
5. In apparatus of the kind referred to in Claim 1 for the electrolytical
decomposition of metallic salts, a reaction vessel such as D of suitable form
arranged to dip into the mercury forming the cathode and the depth of immersion
of which is capable of adjustment substantially as herein before described.
6. In the electrolytical decomposition of a salt the metallic constituent of which
forms an amalgam, with mercury, the generation or production of an electric
current by the decomposition by means of water or other body, of the amalgam
obtained by the electrolytical decomposition of a metallic salt using mercury as a
cathode as set forth.
7. In the electrolytical decomposition of salts, the metallic constituents of which
form amalgams with mercury, a secondary cell having its cathode connected to the
mercury cathode of the primary cell so that this latter cathode or the separated
metal forming an amalgam therewith, constitutes at the same time the anode of the
secondary cell, the arrangement being such that the metal separated at the
mercury cathodes will be converted into a hydrate or other salt by the liquid or
electrolyte placed in the secondary cell and will thus be removed from the sphere
of action of the main current substantially as herein described.
8. In the electrolytical decomposition of salts the metallic constituents of which
form amalgams with mercury, arranging the secondary cell referred to in the
preceding claim, in a circuit in such a manner as to utilize the excess of electric
energy generated in such cell, for the performance of external work substantially
as described.
9. In the electrolytical decomposition of salts the metallic constituents of which
form amalgams with mercury, arranging the secondary cell referred to in Claim 7
in the main current supply circuit for the purpose of utilizing the excess of
electrical energy generated by such cell and thereby enabling the electric energy
supplied from the main source of electricity to be reduced substantially as herein
described.
10. In apparatus for the electrolytical decomposition of salts the metallic
constituents of which form amalgams with mercury, a diaphragm having a thin
layer of mercury therein and constructed by applying a thin layer of chalk upon a
plate formed of a mixture of cement, powdered fireclay and water glass, covering
the said layer of chalk with another layer of a mixture of the kind mentioned,
dissolving out the chalk after the united plates have been hardened, and charging
the thin chamber thus obtained with mercury substantially as described.

page_text: 11. In apparatus for the electrolytical decomposition of salts the metallic
constituents of which form amalgams with mercury, a diaphragm having a thin
layer of mercury therein and constructed by applying a metallic fabric coated
with mercury between two plastic plates formed of a mixture of cement,
powdered fireclay and water glass, and allowing the plates to harden substantially
as described.
12. In apparatus for the electrolytical decomposition of salts the metallic
constituents of which form amalgams with mercury, a diaphragm having a thin
layer of mercury therein, and made by silvering one side of or precipitating a
metal, the amalgam of which is neutral with regard to the electrolyte to be treated,
upon one side of acid-proof and alkali-proof porous plates or sheets of woven
fabric, amalgamating the surfaces thus coated with metal, placing the plates or
sheets with their amalgamated surfaces in contact, subjecting them to pressure to
squeeze out excess of mercury and uniting them substantially as herein described.
13. In apparatus for the electrolytical decomposition of salts the metallic
constituents of which form amalgams with mercury, a diaphragm having
a thin
layer of mercury and made by providing plates or sheets of woven fabric with a
coating of mirror-amalgam substantially as herein described.
14. Apparatus for the electrolytical decomposition of metallic salts, constructed
arranged and operating substantially as herein before described with reference to
and shown in Figs. 2, 3 and 4 of the drawings for the purpose specified.
15. Apparatus for the electrolytical decomposition of metallic salts, constructed
arranged and operating substantially as hereinbefore described with reference
respectively to and shown in Fig. 7; in Fig. 8; in Fig. 9 and in Fig. 10 of the
drawings annexed for the purpose specified.
Dated thin 11th day of October 1892.
W. LLOYD WISE,
Per F. J. Brougham,
46, Lincoln's Inn Fields, London, W.C., Agent for the Applicant.