Improvements in the Electrolytic Production of Caustic Soda, Caustic Potash, and other Products from their Salts.
Year: 1890

page_text: "The decision of the Comptroller-General, of the 22nd day of December 1893, allowed,
under Section 18 of the Patents
fia
sot 1882
Amendment of this
The decision of the Comptroller-General, of the 22nd day of December 1893, allowed,
under Section 18 of the Patents, &c., Act, 1888, on Amendment of this
Specification.
Date of Application, 12th Feb., 1890
Complete Specification Left, 12th Nov., 1890-Accepted, 7th Feb, 1891
PROVISIONAL SPECIFICATION.
Improvements in the Electrolytic Production of Caustic Soda, Caustic
Potash, and other Products from their Salts.
We JAMES CHARLES RICHARDSON of 23 Claremont Square, Clerkenwell in the
County of Middlesex, Electrical Engineer, and TREVENEN JAMES HOLLAND of
lvymeath, Snodland, in the County of Kent, J.P., C.B., Colonel in Her Majesty's
Army, do hereby declare the nature of this invention to be as follows:-
Hitherto, although it is well known that common salt in solution can be split up
by electrolysis into chlorine and caustic soda, there have been draw-backs which
have prevented its extensive application on a coinmercial scale, foremost among which
is the use of porous partitions to separate the products, the resistance they cause to
the passage of an electric current, and their general inapplicability on a practical
scale; and secondly, the polarisation or counter electromotive force which is set up
at the cathode by the hydrogen set free from the decomposition of the water, and
which again, as a gas, introduces additional resistance by covering the surface of
the cathode, and is otherwise objectionable.
According to this invention, these draw-backs in the objects to be attained,
namely, the production of caustic soda or caustic potash, and chlorine, as a gas or
in solution, and hypochlorite of soda or hypochlorite of potash,, or hypochlorite of
the alkali earths (as bleaching powder), are overcome by absorbing the hydrogen
by means of oxide of copper (Cu O) placed next the cathode or electrode at or
near which the caustic soda is formed, the anode being the chlorine electrode.
The effect this simple compound has in the electrolysis of an alkali chloride
(such, for instance, as common salt and chloride of potassium, and the other alkali
chlorides, calcium, barium, magnesium) is remarkable and important economically,
and novel in its peculiar applicability to this subject, from the fact that neither the
oxide of copper nor metallic copper is soluble to any appreciable extent in caustic
soda or caustic potash, nor in their respective chlorides, or any of the other alkali
chlorides; hence it can be employed without loss in this respect.
Other, if not all, commercial metallic oxides, have been tried, including the lead
oxides which nearest approach the oxide of copper for general use, but for con-
tinuous work the oxide of copper excels them all.
The mode of employing the oxide of copper is like the following:-
Having, for example, a shallow tank containing a solution of common salt, the
electrodes are arranged therein. The cathode, which is placed in the lower or
bottom position beneath the anode, is made of copper gauze or iron gauze or carton
or electro-negative metal or element having a large surface (the ganze being
mentioned as giving a large surface, a grid answering in the same way), and in
contact with this is placed the oxide of copper, which may be merely spread over,
pressed in, or agglomerated in the gauze, forming a solid plate.

page_text: The action which then takes place next this cathode may be described thus:-
The anode (of hard carbon rods or other chlorine resisting electrode) being near
the surface of the liquid, chlorine, on the passage of an electric current, is set free
next it, and escapes out of the liquid, first charging the stratum of liquid above
the lowest portion of the anode, and at the cathode caustic soda is formed, and
concentrates at the bottom of the tank, and no hydrogen is given off, for the simple
reason, that in its nascent condition, it combines with the oxygen contained in the
oxide of copper placed next the cathode, as previously mentioned, and forms water,
and the copper is left in the metallic condition, and maintains its good electrical
conductivity throughout, and can be continuously employed by re-oxidation by
heating in air.
In addition to this important chemical part played by the oxide of copper, it
admits of a porous partition being entirely dispensed with in the electrolysis of the
alkali salts for the objects mentioned, and the liquid agitating element in the
gaseous hydrogen is quite prevented, the liquid otherwise next the cathode being
quite quiescent.
If instead of producing a caustic liquid and chlorine, a hypochlorite be desired,
as hypochlorite of soda, it is simply obtained by reversing the position of the
electrodes, placing the anode below the cathode; the chlorine then ascends towards
the cathode, and meets with the caustic soda and hypochlorite of soda is formed,
and may be run off from the top of the solution, and fresh quantities of salt solution
introduced from below, or the electrodes may be arranged vertically.
For experimental demonstration, or where a small quantity of concentrated
solution of caustic soda is required, it is convenient to construct the cathode with
the oxide of copper in contact for vertical use, and to place the anode in an
ordinary porous pot, or between other porous pártitions, the same plan being
applicable on a practical scale, when the porous pot or diaphragm does not offer
much resistance and can afford to be ignored.
A convenient way of producing small quantities of caustic soda or caustic potash
and chlorine solution from their chlorides, is to agglomerate oxide of copper in iron
or copper gauze bent to just fit, say, an ordinary circular battery jar, and pressing
against the inner surface of the jar, and to place the anode of carbon rods, say, in
a porous pot in the centre, both vessels containing a salt solution of equal strength,
but as the solution in the porous pot becomes saturated with chlorine, it is run off,
and fresh quantities of salt liquid and water. are run in. This plan for running off
the solution may be also applied with a horizontal arrangement of electrodes, by
passing a constant stream of water above the anodes slightly charged with salt,
which dissolves the chlorine as fast as liberated. The stream inust be introduced
gently so that the caustic liquid at the bottom not agitated.
If only caustic soda be required, then a soluble anode of iron, zinc or other metal
may be employed, which will reduce the counter electromotive force offered by the
copper, and if positive to copper, it will decompose the salt itself by being joined
up with the cathode, or short circuited, at the same time producing an electric
current in the external wire or conductor, a chloride of the metal then being formed
in the porous pot, and caustic liquid next the cathode, both of which can be run off
automatically.
•
"
'Oxide of copper next the cathode may also be advantageously used in the
electrolysis of other alkali salts, sulphate of soda, for example..
The electric current which is produced when a positive element, is used, instead
of an insoluble anode, and, an external current, may be employed for doing useful
work to which it is applicable, as depositing copper, electric lighting, and the like.
Dated this 12th day of February 1890.

page_text: Improvements in the Electrolytic Production of Caustic Soda, Caustic
Potash, and other Products from their Salts.
We, JAMES CHARLES RICHARDSON of 23 Claremont Square, Clerkenwell, in
the County of Middlesex, Electrical Engineer, and TREVENEN JAMES HOLLAND
of Ivymeath, Snodland in the County of Kent J.P., C.B., Colonel in her Majesty's
Army, 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 :-
.
Hitherto, in the production of caustic soda, caustic potash, and other products
from solutions of their salts, by electrical decomposition, difficulties have been
found to arise on account of the generation of hydrogen at the negative element, or.
cathode.
Free hydrogen not only has necessitated the employment of partitions for
preventing the recombination of the products of decomposition, which, owing to
the disturbance of the solution by the hydrogen gas given off, are caused to come
together again. but the hydrogen has a tendency to create polarisation and additional
resistance, at-the-negative element, to-the-passage of the electric current, by-covering
the surface-thereof.
This resistance, together with; or-even-apart from The resistance enused by the
partitions, has often the effect of precluding the possibility of effecting economically
the electrical decomposition of solutions of alkali salts, for obtaining the products
thereof on a commercial scale.
"
According to this invention, this drawback in the object to be attained, namely,
the production of caustic soda or caustic potash and chlorine, as a gas, or in solution,
and hypochlorite of soda, or hypochlorite-of-potash, or-hypochlorite-of-the-alkali
earths (as bleaching powder), are is overcome by absorbing the hydrogen by means
of oxide of copper (Cu. O) placed next the cathode, or electrode, at or near which
the caustic soda is formed, and hydrogen gas usually generated, the anode being the
chlorine electrode.
The effect this simple compound has in the electrolysis of an alkali chloride
(such, for instance, as common salt, and chloride of potassium,) and the-other-alkali
ehlorides, ealeium, barium, magnesium) is remarkable, and important economically,
and-novel-in-its peculiar applicability to this subject, from the fact that neither the
oxide of copper nor metallic copper is soluble to any appreciable extent in caustic
soda or caustic potash, nor in their respective chlorides, or any of the other alkali
ehlorides; hence it can be employed without loss in this respect.
Other, if not all, commercial metallic oxides have been tried-by us, including-the
lead oxides, which nearest approach the oxide of copper-for-general-use, but for
continuous work the oxide of copper-exeels them all.
The mode of employing the oxide of copper is as follows:-
Having, for example, a shallow tank containing a solution of common salt, the
electrodes are arranged therein. The cathode, which is placed in the lower or bottom
position beneath the anode, is made of copper gauze, or iron gauze or carbon, or
electro negative metal or element, having a large surface (the gauze being
mentioned as giving a large surface, a grid answering the same way), and in contact
with this is placed the oxide of copper, which may be merely spread over, pressed
in, or agglomerated in the gauze, forming a solid plate.

page_text: The action which then takes place may be described thus ;-The anode (of hard
carbon rods or other chlorine-resisting electrode) being near the surface of the liquid,
chlorine, on the passage of an electric current is set free next it, and escapes out of
the liquid, first charging the stratum of liquid above the lowest portion of the anode,
and at the cathode caustic soda is formed, and concentrates at the bottom of the tank,
but no hydrogen is given off, for the simple reason, that, in its nascent condition, it
combines with the oxygen contained in the oxide of copper placed next the cathode,
as previously mentioned, and forms water. The copper is thus gradually converted
into the metallic condition, and maintains its good electrical conductivity throughout,
and can be continuously employed by reoxidising it, occasionally, by heating it
in air.
In addition-to-this important chemical part played by The employment of the
oxide of copper, it thus admits of a porous partition being entirely dispensed with
in the electrolysis of the alkali salts for the objects mentioned, and. the liquid
agitating element in the gaseous hydrogen is quite prevented, the liquid otherwise
next the cathode being quite quiescent.
If, instead of producing a caustic-liquid, and chlorine, a hypochlorite be desired,
as hypochlorite of soda, it is simply obtained by reversing the position of the
electrodes, placing the anode below the cathode; the chlorine then ascends towards
the-eathode, and-meets-with-the-caustic-soda, and hypochlorite of soda is formed,
and may be run off from the-top of the solution, and fresh quantities of salt solution
introduced from-below; or-the-electrodes may be arranged-vertically.
For experimental demonstration, or where a small quantity of concentrated
solution-of caustic-soda-is-required, it is convenient-to-construct the cathode with
the oxide of copper-in-contact for vertical-use, and to place the anode in an ordinary
porous-pot, or between-other-porous partitions;-the-same-plan-being-applicable-on-a
practical seule,-when-the-porous-pot or diaphragm does not offer much resistance,
and can afford to be-ignored.
• A convenient way of producing small quantities of caustic soda or caustic-potash
and-chlorine solution from their chlorides, is to agglomerate oxide of copper in iron
or copper-gauze bent to just fit, say; an ordinary circular battery jar, and-pressing
against-the-inner surface of the jar, and to place the anode of-carbon-rods, say, -in
a-porous-pot-in the-centre, both vessels containing a salt solution of equal strength,
but-as-the-solution in the porous pot becomes saturated with chlorine, it is run-off,
and fresh quantities-of-salt liquid and water are run-in.-This-plan-for-running off
the solution may be-also-applied with a horizontal arrangement-of-electrodes, by
passing a constant stream-of water above the anodes slightly charged-with-salt,
which-dissolves the chlorine as fast as liberated. The stream-must-be-introduced
gently, so-that-the-caustic liquid at the bottom is not agitated.
If only-caustic soda be required, then a soluble anode-of-iron, zine, or-other-metal
may be employed, which will reduce the counter electromotive force offered by the
eopper,-and-if positive to copper, it will decompose the salt itself by being joined-up
with the cathode, or short-circuited,-at-the-same-time-producing an electrio-current
in the external wire or conductor, a chloride of the metal then being formed-in-the
porous-pot, and caustic liquid next the cathode, both-of-which-can-be-run-off
automatically--Oxide of copper-next the cathode may also be advantageously-used
in the electrolysis of other alkali-salts,-sulphate of soda, for example.
The-electric-current which is produced when a positive element is used; instead
of an insoluble-anode-and-an-external-eurrent, may be employed for doing-useful
work to which it is applicable, as depositing copper, electric lighting, and
the like.
In the accompanying drawing we have illustrated, diagrammatically, what may
be used in connection with the herein described process.
a is the
Fig. 1 is a horizontal arrangement, in which t is the containing tank, of slate, for
instance, the level of the salt solution being indicated by the dotted line w.
anode, from which the chlorine is set free, and escapes from the tank by the outlet c
which is connected with a lime chamber for the production of chloride of lime,

page_text: or applied to any other useful purpose. B is the cathode, with the oxide of copper
in contact, where the caustic soda is formed, and collects, and which is drawn off by
the outlet G. Fresh salt solution is supplied by the inlet D. E is the cathode
terminal, and F the anode terminal connected to the dynamo or other source of
electricity. The arrow head → indicates the direction of the electric current through
the solution.
After the oxide of copper next the cathode is exhausted, which is most easily
detected by its metallic condition, it is renewel by removing it from the tank,
washing it to free it from the caustic soda, and then heating in air to its oxidising
temperature, when it will again become ready for further use, and SO
indefinitely.
.
on-
The cathode can be made of iron, but copper or copper plated iron is preferable,
as the iron becomes energetically attacked in a salt solution in the presence of
oxide of copper. an action which is turned to-account-as-will-be-explained further-on.
Of course, any other element as negative as copper can be equally well-used-as-a
enthode, providing its cost is favorable for practical work.
Fig. 2-is-a-horizontal arrangement, in which the position of the electrodes-is
reversed, and indicates the method of forming the hypochlorite of soda--G is the
outlet for the hypochlorite solution: D-is the inlet for the salt (or-other-alkali
ehloride)-solution. c is the outlet for gas, if produced.
Fig. 3 is a vertical arrangement of electrodes, which are -separated from each
other by suitable porous diaphragms or partitions, indicated-by-p-p'- Chlorine-is
set free next the anode (if insoluble) in the chamber H, from which it can be
allowed to escape by the outlet c, or run off as solution, from-the-bottom-outlet-f,
when-it-is-necessary to maintain the salt-solution-supply by the inlet tube D
connected to a suitable source. The chlorine-run-off-in-this-manner-has-some
applications, as for-bleaching, treating metalliferous ores and the like. The soda
colleets-in-the-chamber JJ', or chambers, if the apparatus be multiplied,-from
which it is drawn off by the pipes G-G'.
If, instead of employing an insoluble anode in this form of apparatus with an
outside generated current, it be desired to make the apparatus independent of such
a supply of electricity in the production of the caustic code, it is done by introducing
an element in the place of the insoluble anode, an element-which-will-net-electro-
positively to the copper enthode, such an element being-represented-by zine or iron;
and instead of chlorine being liberated, it will combine with such an element, forming
a chloride, which can be drawn off-and used for any purpose-to-which-it-may-be
applicable. This positive action-only proceeds when the zine, or iron, is joined-up
by an external conductor, as represented by the spiral wire at the top, the arrows
indienting the direction of the electric current, and assumed to be on-short eirenit,
that is to cay, the zine (not to repeat other metals) being allowed thereby-to-do-its
own-decomposing work as rapidly as possible. Its rate-of-decomposition, however,
ean be easily regulated by introducing desired resistances in-the-outside-conductor,
and these may take a useful shape, as in driving a motor, an electric lighting circuit,
copper depositing baths, or anything of the like, to which it can be applied, with or
without alteration of its potential by transformers: The rate of forming the eaustie
soda next the enthode depends upon the rate of action of the zine. If the zine be
employed-together with an externally supplied-current, as from a dynamo, then
its action is thereby increased, but no chlorine is set free, as happens-with-an
insoluble anode, when the electric-power-required is greater.
Fig. 4 represents a vertical-arrangement-with-insoluble-anode-for-the-production
of hypochlorites.
Having now particularly described & ascertained the nature of our said inven-
tion, & in what manner the same is to be performed, we declare that we do not claim-
generally the employment of oxide of copper as a depolarising agent in electrolysis of
alkali salts, but what we claim is :-
In the electrical decomposition of salts of alkali or alkali earths in solution, the

page_text: employment of oxide of copper (Cu 0) substantially as described for the purpose set
forth, without and in lieu of a partition or diaphragm between the electrodes.
Dated this 12th day of November 1890...
NEWTON & SON,
Agents for the Applicants.