Improvements in Apparatus for use in the Electrolytic Decomposition of Metallic Salts.
Year: 1890

page_text: Date of Application, 9th Dec., 1890-Accepted, 31st Jan.,
1891
[Communicated from abroad by ISAIAH LEWIS ROBERTS, of Brooklyn, New
York, Electrician, and THOMAS HENRY MCGRAW, of Poughkeepsie, New
York, Gentleman, both in the United States of America.]
Improvements in Apparatus for use in the Electrolytic
Decomposition of Metallic Salts.
I, HENRY HARRIS LAKE, of the firm of Haseltine, Lake & Co., Patent
Agents, 45 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:-
Prior to this invention it had been proposed to decompose or purify by electro-
lytic action solutions of the metallic salts." In some of the processes proposed, the
anode and cathode were both placed in a single chamber or compartment of a vat
or cell containing the solution to be decomposed, while in others a porous jar or
diaphragm such as those commonly used in galvanic batteries was to be interposed
between the two electrodes. No such apparatus, however, which has been used for
this purpose has been capable, so far as I know, of dissociating and recovering in a
pure state or to any practical extent the elements of the solutions under treatment,
as for example, in obtaining alkaline hydrates from saline solutions. This is due
mainly to the tendency of the elements after their dissociation by electrolytic action
to intermingle and produce chemical recombinations.
To avoid this obstacle to the production of substances of high chemical purity
by the electrolytic decomposition of solutions of metallic salts I use a diaphragm or
partition interposed between the two electrodes, which is impervious or practically
so, to the solutions used and permits their diffusion and intermingling but does not
prevent or materially impede electrolytic action. Such a diaphragm I define as a
ໄ non-porous or impervious, electrolytic diaphragm."
These diaphragms may be made in many different ways and of various substances,
the following examples serving as illustrations of the nature of the same.
The electrolytic tank may be divided into two compartments by a partition
formed of a paste, made by boiling starch with a solution of chloride of sodium or
common salt, and held in place by pieces of felt, cloth, porous earthenware plates or
other means.
Another way to make the partition or diaphragm is to soak, for several hours, a
plate or jar of baked earthenware or a sheet of felt in an aqueous solution of alum,
and then immerse it in a solution of alkali, such as caustic soda, until, by the
action of the same upon the alum, the pores of the porous plate are filled with a
gelatinous mass.
Another way to make the partition is to use two supporting walls of earthenware,
canvas or other porous material and to fill in the space between them with a paste
made of slaked lime, care being taken not to leave any air spaces or holes in the
mass.
These diaphragms or partitions may also be made in the following manner :-
Cut out two pieces of asbestos board of the desired dimensions and lay them on
opposite sides of a piece of woven asbestos cloth of about the same shape; then
sew or fasten them up in a covering or bag of cotton cloth or the like; then expose
the whole for about twenty four hours to the action of a solution of an acid, such
as muriatic acid of about twelve degrees Baumè; then squeeze or roll them and
gain treat them with the acid; then roll and knead the bag in fresh water until
he salts or soluble portions resulting from the action of the acid are thoroughly
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page_text: washed out; then subject the bag to pressure to free it of surplus moisture and gas,
to reduce its bulk and to flatten it out. It this then ready for use.
Still another way of making these partitions or diaphragms, and for the com-
mercial use of the invention probably the best, is to use anthracite coal reduced to
an impalpable powder and packed in between porous plates or held in any other
proper way in a receptacle and interposed between the electrodes.
Many other materials may be used, such as wheat flour, amorphous silica, or
pulverized set plaster, but from the above it will be seen that all of the different
diaphragms or partitions described have certain characteristics in common. They
are either gelatinous or composed of substances in such a finely divided condition as
to be practically amorphous. To these qualities they owe their impermeability to
fluids, while the moisture which they contain or which they are capable of taking
up and retaining renders them conducting or electrolytic. By the use of such
partitions or diaphragms transfusion or intermingling of the fluids is prevented but
electrolytic action is not appreciably interrupted.
While under normal conditions, diaphragms of this kind prevent the passage
through them of fluids, the mere fact of their impermeability does not appear to
be the only reason for the results obtained by their use. If the attempt be made,
for example, to decompose an electrolyte by using an ordinary porous diaphragm
and an anode that is not attacked by the solutions or the products of decomposition,
the tendency of the liberated acid radical and bases to recombine, will not be
materially impeded, and the process will consequently be of little value. On the
other hand, while an impervious diaphragm, such as above described, may prevent
the actual transfusion of fluids, yet, if it be very thin, a recombination of the
elements appears to take place through the diaphragms, and in some instances, as
where a metallic and decomposable anode is used in the body of the diaphragm itself
destroying after a time its conductivity and rendering it useless.
This led to the discovery of what appears to be a property of these partitions or
diaphragms, and in fact, of all others, which has never before been taken advantage
of in processes in which it is desirable to obtain products by electrolysis of approxi-
mate chemical purity. This discovery is that these diaphragms offer a resistance
to electrolytic action as well as to the passage of the electric current, which
electrolytic resistance increases with the thickness or mass of any given partition or
diaphragm.
As an example, if a cell containing electrodes of hard carbon or platinum be
divided by an ordinary thin porous partition and filled with a solution of common
salt, a current passed through it operates to transfer the chlorine radical to the
anode chamber and to liberate hydrogen at the cathode, but in practice, it will be
found, under such conditions, that but little gas actually escapes at the cathode and
that the chlorine radical merely recombines with its base, for which it has apparently
a stronger affinity than for the hydrogen.
But by increasing the electrolytic resistance of the diaphragm, which as before
stated, may be done by increasing its thickness independently of or without regard
to its true electrical resistance, this tendency to recombination is proportionately
overcome and practicable and useful results obtained. For instance, commercial
caustic soda may be obtained in this manner by the use of a diaphragm of about
five centimetres in thickness, which it is desirable to construct in such manner as to
secure as low an electrical resistance as practicable.
To define in general terms, therefore, this feature of the invention, and assuming
that heretofore these partitions or diaphragms when used have had a relatively low
or practically no electrolytic resistance, it may be stated as consisting broadly, in
the employment with the electrodes of an electrolytic cell of a partition or diaphragm
of a relatively high electrolytic resistance.
In the case of an electrolytic tank or cell containing two chambers or compart-
ments filled with solutions, the thickness of the diaphragm, as above stated should
be about five centimetres or more but the actual thickness in all cases that is
necessary to the attainment of the best results will obviously vary.

page_text: It is obvious that in increasing the electrolytic resistance of the partition it is
undesirable to increase the electrical resistance, but with the ordinary forms of
diaphragm or partition this would be scarcely possible.
The partitions above described, however, which are composite in their character,
that is to say, which consist of a support or frame containing or sustaining a suit-
able substance that will permit the proper electrolytic action to take place through
it without adding injuriously to the electrical resistance of the cell, obviate this
objection.
The tendency of the dissociated elements to recombine in the body of a com-
paratively thin impervious partition or one of low electrolytic resistance may be
counteracted to some extent by the use of two or more of such partitions with a
proper electrolyte between them. This is particularly the case where an anode
that combines chemically with the transferred acid radical is used. In such cases
any recombination or chemical action that may take place by the passage of the
elements through the diaphragms will occur mainly in the body of the electrolyte
between the two partitions.
The principle of the construction of the apparatus and the particular form of the
same which is best adapted for practical use are illustrated in the drawings in which
Figure 1 is a sectional view of a simple form of tank showing an impervious
diaphragm.
Figure 2 is a sectional view of a modification.
Figure 3 is a vertical section of an asbestos diaphragm.
Figure 4 is a vertical section of a tank in which such diaphragm is adapted
for use.
Figure 5 is a vertical sectional view of the preferred form of apparatus for com-
mercial use.
Figure illustrates an ordinary tank or receptacle A, containing two elec-
trodes B, C, of platinum or other suitable material separated by an impervious
electrolytic partition or diaphragm.
The diaphragm in this case consists of two sheets of asbestos or cotton cloth D, D,
supported by a frame E. These form supporting or containing walls for a mass of
boiled starch paste, gelatinous slices or similar compound F, which forms the
diaphragm proper.
If a solution of a metallic salt, such for example, as chloride of
sodium, be placed in the two compartments, and the electrodes connected to a
source of current, chlorine gas will be given off at the anode while the sodium base
in the cathode chamber in presence of the water becomes sodium hydroxide or what
is commercially known as caustic soda. If a decomposable anode be used, such as
an anode of iron, the chlorine radical will combine with it forming chloride of
iron. In this way other alkalis and metallic salts may be produced.
In Figure 2 the tank A contains an anode B, and a cathode C, each surrounded
by a diaphragm or partition F. The diaphragms in this case are composed of jars
of porous earthenware filled with a gelatinous substance, as above described, and
between them is an electrolytic fluid, such as brine.
Figure 3 represents a diaphragm made of asbestos, treated as above described,
H is the outside bag or covering of cotton cloth, I, I are the two asbestos boards
and J is the intermediate sheet of asbestos cloth.
When such a diaphragm is used it is advisable to employ a form of tank sub-
stantially like that shown in Figure 4.
KK, are two pieces of insulating material upon which, as bottoms, two boxes
are built, L L represent the sides of one, and these are composed of slate or other
insulating material not sensibly attacked by the products of decomposition. The
other sides M M may be of wood. The two boxes are laid together with the
diaphragm between them and secured by rods. A compartment will thus be
formed on each side of the diaphragm in one of which there is a copper plate con-
nected with a suitable terminal and in the other are anodes O, of carbon or other
material of proper character.
To facilitate the evolution of gas the anode compartment is filled with a finely

page_text: a saline
divided coke or similar material that will not be affected to any material extent by
the products of decomposition. This coke is moistened with acid or
solution to make it a better conductor. The mass of coke serves also to sustain the
diaphragm against the pressure of the solution in the cathode chamber. Being
packed closely into the anode compartment, the coke makes a good conductor from
the diaphragm to the anode conductors O, and electrolysis, with the evolution of
takes place through it.
gas
The coke compartment is provided with an outlet K' for the gas, and the other
compartment has an inlet L' and outlet M¹ for the solution. The inlet L' serves
also to permit the escape of gas. This tank is placed in another slightly larger,
and the intervening space is filled in with tar or similar material.
By this apparatus, if a solution of chloride of sodium or common salt be
introduced into the cathode compartment and a current passed through the vat,
hydrogen will pass off through the opening L', chlorine gas through the outlet K',
and caustic soda will be formed in the cathode chamber. The diaphragm prevents
the escape of the solution into the anode chamber and the recombination of the
products of the electrolytic action.
This plan of construction of the electrolytic apparatus has many advantages.
Heretofore in apparatus of this kind, both electrodes have been immersed in an
electrolytic solution, but much better results are obtained by filling the anode
chamber with moist powdered carbon or by packing the anode in a suitable
receptacle with a finely divided substance carrying sufficient acid or saline
solution to render it electrolytic, and which will permit the gas to pass off
freely from the surface of the anode. This plan of construction is that which
I prefer to use in practice for the manufacture of caustic soda from brine, and
it is shown in Figure 5.
A is a cast iron vessel of the desired capacity which serves as the cathode
as well as the tank or vat in which the solution to be decomposed is contained.
A¹ is a cover fitting air-tight on the vessel.
In said cover is a neck or contracted opening surrounded by a rim or flange A".
There may be more than one of these openings provided the tank be of sufficient
dimensions to render it necessary.
To introduce the solution into the receiver A, there is an inlet P, provided
with a valve or cock and an outlet P1 is used to draw off the caustic alkali
after the process of decomposition has been carried on for a proper length of
time.
The anode proper is a pressed or moulded cylinder B, of carbon.
To the upper rim or edge of the neck A is secured in any proper manner,
as by means of a ring or hoop Q, a bag Q, which, when the cover A' is in
place, reaches nearly to the bottom of the tank A. This bag may be made of
some textile material, preferably of cotton strengthened by asbestos cloth, wire
gauze or any such material that will not be attacked by the solution or the
electrolytic products.
The anode B is passed down into this bag, and the space around it, up to
a point slightly above the normal level of the solution in the tank A, is filled
in with anthracite coal reduced to as finely a powdered condition as possible
and packed in around the anode.
The anthracite coal is to be ground in such manner as to reduce it to the
condition of a practically amorphous or impalpable powder. In this condition,
when packed in around the anode, it forms a practically perfect barrier to the
mechanical transfusion of fluid. In other words, no solution or liquid of any kind
under normal conditions will strain or ooze through it, even by the action of
osmose, and in this sense it may be called non-porous as distinguished from those
substances heretofore employed as diaphragms, which are, in whole or in part,
distinctly porous and permit the passage or transfusion of fluids through them.
The mass of coal dust or powder, however, while it is itself, practically, a non-
conductor of electricity interferes to no perceptible extent with electrolytic action

page_text: and the transference of the acid radica to the anode, since 16 15 moistened
throughout with the solution in the vat.
It will be found, however, that under the action of the current a certain quantity
of water and acid is carried through the mass of coal dust and accumulates in the
anode compartment around the carbon cylinder and rises above the level of the
solution in the outer or cathode compartment.
To avoid the very objectionable consequence of this peculiar action or property of
the current of forcing or carrying along with it the water through the otherwise
normally impermeable barrier of coal dust, there is packed into the bag Q', for a
short space above the coal dust S, and within the neck A", a quantity of grains of
plumbago, pebbles, broken glass, retort carbon or the like.
From this mass runs a pipe S', which serves the two-fold purpose of a passage
for the escape of the gas generated by the electrolytic action and also as an
overflow to carry off the water which might appear in the anode compartment
from the cause above explained.
Around the carbon cylinder B, within the neck A" and extending down into
the mass of powdered coal S, or whatever material may be used in its stead, for a
short distance below the level of the solution in the outer or cathode chamber is a
cylinder R, of glass or other material not attacked by the products of decomposi-
tion. Within this cylinder is the granulated coke, pebbles, or plumbago, T, and
the end of the gas and overflow pipe S' is carried through the side of the cylinder R,
and into the mass of coke T.
The remaining space above the coal dust S, in the bag Q¹, both inside and
outside of the cylinder R, is then sealed with a filling or luting of asphaltum
or other suitable material.
By this means any return of water through the bag Q, or other injurious
consequences of the carrying up of water around the cylinder B is entirely avoided.
The glass cylinder extends down below the level of the solution in the outer
compartment and as the water cannot return against the electrolytic action which
produces it at or on the surface of the cylinder B, it can only pass up into the
cylinder R to the layer of coke T, from whence it runs off through the pipe S¹
With regard to the operation and manner of using this apparatus, it may be
stated that successive charges of brine are run into the outer or cathode chamber,
and when the current is applied, the action, as I have observed it, is to transfer the
acid radical through the packing of coal dust to the anode B, where it is given off
as chlorine gas. This gas rising or accumulating in the stratum of granulated
carbon T, is conveyed off by the pipe S. The solution of caustic alkali left in the
tank A is drawn off when of sufficient strength and replaced by a fresh charge.
In some of the forms of the apparatus, such as those shown in Figures 1 and 2,
a decomposable anode is used to take up and combine with the acid radical, but it
is preferable to make provision, as by means of the apparatus shown in Figures 4
and 5, for the giving off of the radical as gas. A difficulty is met with in such
apparatus, however, in obtaining a substance that will not be attacked and
materially affected by the gas or by the electrolytic action.
The best and most practicable anode of which I am aware is made in the
following manner.
A quantity of carbon, preferably plumbago and retort carbon, is comminuted or
reduced to a fine powder and to it is added a quantity of paraffin or ozokerite in
proportions which may greatly vary as will be hereinafter seen. The mass is then
heated until the paraffin is melted into a thin fluid and then thoroughly mixed
together.
While it is still hot, the mixture is moulded into the desired shapes of plates or
bars, under a pressure sufficiently high to force the particles of carbon into intimate
contact, and to express all excess of the paraffin. The forms are then allowed to
cool, preferably under pressure, and when the paraffin becomes hard they are ready
for immediate use.
A number of substances other than those named, may be employed as the

page_text: binding material, such as sulphur, chloride of lead, and others which are reduced
to a liquid condition by heat, and which on cooling return to a solid condition.
The term "liquid " is used in this connection, as distinguished from the broader
term "fluid" and in its proper significance as implying a perfectly mobile state,
and from the more restricted term "viscous" and as expressing a condition which
permits the surplus or excess of the binding material to be expressed by pressure.
An ordinary viscous fluid could not be used in making these carbons, even though
it solidified on cooling, for it would not permit the carbon particles to be forced
into actual contact, since practically the whole amount incorporated with the
carbon would remain in the mass, and could not be squeezed out.
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 correspondents I declare that what I claim is :-
First. In an apparatns for the decomposition of metallic salts, the combination
with the electrodes of an electrolytic diaphragm or partition, substantially non-
porous or impervious to the solutions, as set forth.
Second. In an apparatus for the decomposition of metallic salts, the combina-
tion with the electrodes of an electrolytic diaphragm or partition amorphous in
structure, as set forth.
Third. In an electrolytic cell or apparatus the combination with the electrodes
of two or more electrolytic partitions of non-porous substances, forming compart-
ments for the electrodes, and one or more electrolytic bodies interposed between
the partitions, as set forth.
Fourth. In an electrolytic cell, the combination with the electrodes of an
intermediate partition or diaphragm having a relatively high electrolytic resistance,
as set forth.
Fifth. In an electrolytic cell, the combination with a cathode and an anode not
decomposable by electrolytic action of a non-porous partition of high electrolytic
resistance interposed between the electrodes, as set forth.
Sixth. A composite diaphragm or partition for electrolytic cells composed of
supporting or containing walls with an intermediate filling, as set forth.
Seventh. An electrolytic apparatus, consisting of a tank or vat divided by an
electrolytic diaphragm or partition into two compartments containing conductors or
electrodes, one of said compartments being adapted to contain the solution to be
decomposed, and the other compartment filled with a finely divided substance not
decomposable by the electrolytic action, as set forth.
Eighth. In an electrolytic apparatus, the combination with a cathode of an
anode packed or embedded in a material such as powdered anthracite coal, or its
equivalent.
Ninth. In an electrolytic apparatus, the combination with a cathode of an
anode packed or embedded in powdered anthracite coal contained in a receptacle in
the tank or vat, as set forth.
Tenth. A seal tank or vat for electrolytic deposition provided with an outlet and
with an over-flow for fluids, both leading from the anode compartment, as set
forth.
Eleventh. The combination, with a closed cathode compartment, of a closed
anode space or compartment, a gas discharge and an overflow pipe for water
leading from the anode compartment and above the level of the solution in the
cathode chamber as set forth.
Twelfth. The combination, with a closed iron vessel or receiver constituting the
cathode, of the bag or receptacle extending into the same, the carbon anode contained
in said bag and the filling of coal dust surrounding the anode, as described.
Thirteenth. The combination, with the iron tank or receiver and the cover
having a flanged opening or neck, of the bag or receptacle secured in the neck, the
carbon anode and the filling of coal dust surrounding the same and contained in
the bag.

page_text: Fourteenth. The combination, in a closed tank or vat with an anode surrounded
by a substance such as coal dust, a gas chamber or space above the same filled
with granulated carbon or other non-decomposable granular substance, and a pipe
leading therefrom for conveying off the gas, as set forth.
Fifteenth. In a sealed tank or vat for electrolytic decomposition, the combination
with the anode embedded in or surrounded by a substantially non-porous
electrolytic body of an impervious cylinder around the anode extending below the
level of the solution, a layer of granulated carbon or its equivalent between the
anode and the impervious cylinder above the level of the solution, and an outlet
pipe extending from the same.
Sixteenth. In a sealed tank or vat for electrolytic decomposition, the combination
with an anode and a cathode and a substantially non-porous electrolytic diaphragm
separating the same, of an impervious cylinder around the anode extending down
below the level of the solution, and an outlet pipe for gas and water extending
therefrom above the level of the solution in the tank or vat, as set forth.
Dated this 9th day of December 1890
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C., Agents for the Applicant.