Improved Apparatus and Process for Electro-chemical Decompositions.
Year: 1894

page_text: Date of Application, 24th Apr., 1894-Accepted, 14th July, 1894
COMPLETE SPECIFICATION.
Improved Apparatus and Process for Electro-chemical
Decompositions.
I, HENRY CARMICHAEL, of Malden, Middlesex County, Massachusetts,
United States of America, Analytical Chemist, do hereby declare the nature of
my invention for IMPROVED APPARATUS AND PROCESS FOR ELECTRO-
CHEMICAL DECOMPOSITIONS, and in what manner the same are to be practised,
to be particularly described and ascertained in and by the following statement :-
The object of my invention is to render electro-chemical processes in general
more productive and commercially more valuable than they have been heretofore.
The more particular aim of my invention is the provision of economical means
for electrolysing aqueous solutions of various chlorides notably the solution of
common salt.
Hitherto, methods of and apparatus for electrolyses of chlorides have been of
little more than scientific interest, and of scarcely any commercial value, so far as
known to me.
The contrivers of methods and apparatus for this purpose have been to a great
extent baffled by the obstacles opposed by the chemical peculiarities of the
substances resulting from the electrolyses; to separate the elements of a solution by
electro-chemical means is not difficult, but to manage the elements separated has
been and is a matter of so great difficulty that none of the methods used heretofore
can be called commercially successful.
A typical illustration of the behaviour of the ions or products of electrolyses of
chlorides is afforded by the process of separation of the clements in a solution of
common salt by means of an electric current. Represented by chemical symbols the
well known electro-chemical separation is this.
NaCl + H2O = Na + H2O + Cl.
The sodium liberated at one electrode immediately decomposes the water of
solution, forming the hydrate, or caustic soda;
Na + H2O = NaHO + H.
The available products of the electrolyses are, then, sodium hydrate (NaHO),
chlorine (Cl), and hydrogen (H).
So, although properly speaking metallic sodium is the cation resulting from the
process, the hydrate may be considered as the cation, since usually it is the only
substance apparent at the cathode, if we disregard hydrogen.
I am aware that in many electrolyses the true ion, or liberated element, does not
preserve its chemical integrity, but re-combines with substances in solution. For
convenience, however, I desire to use the word "ion" to mean whatever substance
is sensibly present at either electrode, whether it be the elementary ion as usually
understood, or a secondary combination of the elementary iou.
The ions are liberated apart upon the electrode surfaces but being soluble and
diffusive they are soon brought together in the aqueous electrolyte between the
poles where they enter into chemical combination. The fluid currents engendered
by the escaping gases actively assist the mingling and combination of the
electrolytic products.
Sodium hydrate and chlorine form either sodium hypo chlorite, chlorite or
chlorate according to temperature or other conditions. These uniting with
hydrogen at the cathodes are resolved into chloride of sodium and water, which is
the very solution originally decomposed.

page_text: At the outset then, necessity arises to keep the ions separate and to overcome or
check diffusion and circulation, whereby they are intermingled and recombined to
form the original electrolyte.
To accomplish this object has been the aim of various methods of electrolyses.
These may be divided conveniently into two classes :-One wherein the means
for separating the ions is mechanical; the other wherein chemical means are
employed.
In most of the mechanical methods a diaphragm has been interposed between
the electrodes to prevent the passage and intermingling of the ions. Such a
diaphragm should be porous so that an unbroken column of electrolyte stands
between the electrodes, and further should be of such dimensions and substance as
to offer the least possible resistance to the passage of an electric current.
Chemical methods of separation have employed some substance for which one
of the ions has strong chemical affinity. This substance placed at the electrode
where the ion to be secured is delivered arrests the ion by forming a new
compound with it as fast as it appears at the electrode. In addition to the expense
and complication of such a process if the ion itself is the product desired, such a
chemical method while removing one difficulty creates another, for the combination
of the ion with the chemical arrester must be redecomposed by a subsequent
auxiliary process.
The object of this invention is to render the mechanical separation of ions.
feasible and consistent with economical production.
Mechanical operators have been unsuccessful commercially for this reason among
others; because the ions in solution have not been obtained in a concentrated state
without great waste of electric current. If the electrolyte is common salt and the
desired ion caustic soda, as soon as the caustic soda becomes concentrated at the
cathode its diffusive tendency increasing proportionately causes it to pass through
the electrolyte in spite of the interposition of a porous diaphragm, until it reunites
with the chlorine set free at the anode.
Moreover all the porous diaphragms hitherto employed have proved short-lived,
because unable to resist the continued action of caustic soda; an apparatus
employing such a destructible diaphragm is expensive to maintain and unreliable
in use. Again, the anodes proposed for the purposes have not been such as answer
the requirements of practical manufacture.
By the process and apparatus of my invention herewith described the obstacles
above mentioned are overcome so far as to enable the manufacturing chemist to
obtain the products of electrolyses in the state in which they are liberated at the
electrode so that no further chemical process is necessary, and so that the ions are
delivered continuously from the electrolytic cell in concentration sufficient for
industrial purposes and with an efficiency of electric current very near the
theoretical.
By decomposing a strong solution of common salt by this method there can be
obtained caustic soda in solutions containing from 250 to 350 grammes or more of
caustic soda to the litre, chlorine in equivalent quantities, and hydrogen as a
by-product, with an efficiency of electric current of 90 % and upwards.
Following is a description of the method and apparatus which are my invention,
as applied, first to the electrolyses of solution of sodium chloride; second to the
electrolyses of sodium sulphate; but I wish it to be understood that my method
and apparatus are adapted to the electrolysis of any available solution.
In the accompanying drawings which form part of this Specification
Fig. 1, is a vertical longitudinal section of an electrolytic cell suitable for
commercial production of caustic soda, chlorine and hydrogen.
Fig. 2 is an end sectional and perspective view of the apparatus shown in Fig. 1.
Fig. 2 is an end sectional view of the apparatus of Figs. 1 and 2, showing on a
larger scale the structure and arrangement of the containing-cell and diaphragm.
Fig. 3, shows in section and perspective an insulated leading wire which is a
detail of the apparatus.

page_text: PP
Fig. 4 shows on a larger scale a section of part of the apparatus of Fig. 4.
Fig. 5, is a horizontal section of the apparatus shown in Fig. 4 on the line 3, 4.
Fig. 6, shows the cellular base of the apparatus of Figs. 4 and 5, in perspective.
Figs. 7, 8, and 9, show details of the apparatus of Figs. 4 and 5. Fig. 8 is a
section of part of the apparatus of Fig. 5 at the line y'.
Fig. 10, represents a battery of electrolytic cells, arranged in electric series,
together with auxiliary apparatus.
Fig. 11, shows in vertical section a small apparatus for the electrolyses of sodium
sulphate.
Figs. 1 and 2 show a recatngular form of my electrolytic cell, consisting of a box
of glass, slate or other suitable non-corrodible material. The box is double and is
composed of an upper and a lower portion designated respectively U and L in
Figs. 1 and 2. In the compartments U and L of the apparatus is placed the liquid
to be electrolysed.
The compartments U and L are separated by a diaphragm D, which is inclined
to the horizontal. In Fig. 2 the diaphragm D is shown inclined in two directions
like an inverted house roof.
دو
This diaphragm, and its counterpart in all apparatus used in connection with my
process, is, generally speaking, concavo-convex. "Concavo-convex as understood
by me and applied to this description of my invention, does not involve a spherical
surface merely, but defines broadly the construction of a diaphragm which may be
pyramidal, or prismatic, as in Fig. 2, or conical, as in Figs. 4 and 11, or which
might be arranged in a very large apparatus as a series of prismatic folds, forming
a number of corrugations.
This diaphragm should be of a porous inert material and should be made as thin
as is consistent with necessary strength.
In each of the compartments U and L is situated one of the electrodes of the
cell, the anode in the compartment U, the cathode in the compartment L.
Platinum is the best material for the anode, but if the high cost of platinum is an
obstacle to its use, gas carbon or some mineral conductor may be employed with a
few leading wires of platinum. The anode of Figs. 1, 4, 5 and 11, is shown
composed of lumps of gas-carbon G, which rest on platinum wires W, which
connect with the leading wires.
The cathode is of iron, made preferably in such form as to serve for the base of
the compartment L. The cathode base is shown at B in the figures; its electric
connection is at K. The inner surface of the cathode base B is preferably inclined
to the horizontal and corrugated so that the gases of decomposition may escape
readily and not polarize the cathode.
The walls of the compartment U (which in Figs. 1 and 2, is smaller in
horizontal area than compartment L) extend down into the compartment Las
shown in Figs. 1 and 2.
The surrounding walls of the compartment L are surmounted by a cover c,
which closes the compartment L by forming tight connections on all sides with the
walls and u. The walls and u and the cover c enclose a space or chamber H
whose function will be described presently.
The outer edges of the diaphragm D are secured on all sides to the lower edges
of the walls u in such manner as to form a tight joint.
The electrolytic cell is restricted in but one dimension, that is, its height. To
remove the electrodes too far from one another would result in decrease of efficiency
in the apparatus by reason of the consequent increase in the internal resistance of
the cell. In operating with an apparatus similar in construction with that shown
in Figs. 1 and 2 it has been found desirable to support the anode about 24 inches
above the diaphragm and to bring the cathode as near the lower surface of the
diaphragm as possible. This space of 24 or 3 inches appears to be ample for the
isolation of the ions under the conditions of use and arrangement of cell as here set
forth.

page_text: 11, however, it is desired to obtain ions in an extraordinarily high state of con-
centration at the expense of electrical energy, this distance between electrodes may
be increased to suit the operator.
The electrolytic cell is filled with a strong solution of common salt to a level
about an inch above the anode. The electric current is turned on and the familiar
decomposition begins.
At the anode G, chlorine is disengaged from the solution and rises to the top
of the compartment U. Some of the chlorine is retained in solution in the
electrolyte.
At the cathode in the compartment L under the diaphragm D, sodium hydrate
is formed and hydrogen is liberated. The diaphragm D prevents the hydrogen
from rising through the electrolyte to the chlorine region. By its inclination the
diaphragm D guides the liberated hydrogen into the chamber II, whence it escapes
through a tube h to a suitable receiver.
The hydrogen is delivered at h under such pressure as is necessary to keep the
Ievel of the liquid in the chamber H from rising to the tube h. The interposition
of the diaphragm D between the compartments U and L serves two purposes;
First. The hydrogen is not allowed to mingle with chlorine at the top of the cell
and thus form an explosive mixture; and, second, the ebullition of hydrogen is
prevented from carrying the sodium hydrate into the presence of chlorine.
As described so far the electrolyses in this apparatus has not differed in method
from that of known apparatus. It is not in the formation of the ions that this
process differs from others, but in the subsequent mode of disposing of the ions so
as to obtain them in the condition in which they have been developed at the
electrodes, without interrupting the process of electrolysis. Nor is this the first
electrolytic apparatus wherein a diaphragm has been employed. But the
electrolytic cells known heretofore have employed diaphragms only to interrupt
the flow of gases of electrolyses and by that means to prevent stirring by ebullition.
The diaphragm used in the apparatus described differs radically in structure
from those used heretofore and combines the requisites of porosity, conductivity
and strength.
A diaphragm which shall combine the above three requisites and also possess the
ability to resist the action of caustic soda is constructed as follows:
A cement-like silicate, as for instance hydraulic cement, is moulded to the form
desired for a diaphragm. To give the silicious sheet sufficient flexibility and
strength, it may be enforced with fibres or a textile fabric of suitable form and
strength. Asbestos fibre or asbestos cloth is preferred for the purpose, as being
unaffected by the action of caustic soda. It is not absolutely necessary to use a
resistant fibre, as the surrounding silicate protects the fibre from chemical actions
until the silicate itself which forms an insoluble double silicate becomes so hard as
to require no support.
An easy method of constructing a diaphragm is to fill the meshes of a sheet of
asbestos cloth with the silicate, and mould this cloth to the form desired.
Continued use has proved that a diaphragm of this construction is perfectly
porous, interposes no appreciable resistance, and under ordinary working circum-
stances is indestructible.
As the solution of caustic soda in the compartment L increases in strength with
each increment from the cathode it slowly diffuses up through the diaphragm D,
and if allowed to accumulate indefinitely would ultimately join the chlorine at the
anode.
Thus, after the apparatus has been in operation a short time there are formed
several horizontal zones of various compositions and density. At the top of the
compartment U free chlorine collects in the space CL, whence it may be drawn
through the pipe cl. The electrolyte in the compartment U divides itself into
three horizontal zones. The uppermost zone Z' lies just above the anode and is
charged with chlorine in solution. This zone Z'may be known as the chlorine
.zone.

page_text: Chlorine gas does not readily enter into solution in salt water especially if the
solution is warm. Observation of the apparatus described has shown that the
chlorine in the zone Z¹ has no sensible tendency to diffuse downward through
the electrolyte even though the process be continued uninterruptedly for many
days. No precaution, therefore, need be taken against the downward travel of
chlorine. If the upward diffusive movement of caustic soda is prevented or
counteracted the object of keeping the ions asunder will be accomplished.
Below the anode is the zone Z, filled with a solution of common salt untinged
by chlorine and free from diffusing caustic soda. This zone may be referred to as.
the chloride or electrolyte zone.
Below the zone Z is the zone Z occupied by diffused caustic soda and electrolyte
which as the concentration below the diaphragm D increases spreads upward
toward the zone Z. In an apparatus operating under ordinarily good conditions.
these zones are clearly defined to the eye.
The chlorine zone at and above the anode is colored greenish yellow; the
chlorine zone is clear, and the diffused soda zone is clouded, on account of the
presence of lime and magnesia as slight impurities in the electrolyte which are
precipitated by the alkali.
Below the diaphragm D is the region within the compartment L, marked NA,.
filled with concentrated caustic soda which slowly but constantly diffuses through
the diaphragm to the diffused soda zone Z³.
It has been intimated already that chlorine has but little tendency to diffuse
downward through a common salt solution even when assisted by the portative
effect of an electric current. As the resistance of the electrolyte to the passage.
of the electric current warms the electrolyte the chlorine still less readily diffuses.
through the liquid. Therefore the task of keeping the ions separate is reduced
to keeping the hydrate at the cathode from diffusing upward.
The experience of chemists and the experiment and observation of the inventor
show that neither the diaphragm nor the great specific gravity of caustic soda,.
nor the two in combination, can prevent the diffusion of caustic soda through the
electrolyte.
To the influences already at work to keep the caustic soda in the lower zones
of an electrolytic cell the process invented and herein described adds a third which
effectually keeps the caustic soda within limits consistent with the continuous.
efficiency of the process. Though the superiority in weight of the caustic soda.
solution over the common salt solution is not a bar to upward diffusion of caustic
soda, yet this difference in weight may be utilized to cause a constant downward
displacement of the caustic soda; and this downward movement of the mass is.
adjustable to the rate of upward diffusion of the caustic soda. The relative width
of the zones Z³ and Z³ is preserved constant by means of continuous downward
movement of the individual particles in solution. Following is a description of
the method and means by which this adjustment is effected.
At some point in the chloride zone Z' a solution of common salt, of the same.
strength as the original electrolyte is introduced. This has no tendency to flow
upward and displace the liquid in the chlorine zone, which is of the same specific
gravity as the fresh electrolyte, nor to flow down through the soda which is.
heavier than the incoming salt solution.
The downflow of the liquid in the zones and Z' as a mass is caused by
allowing caustic soda to flow out from the zone NA as the common salt solution is.
introduced into the zone Z. The apparatus by which this adjustment of flow in
mass to molecular diffusion is effected is shown in Figs. 1 and 2.
A pipe P is introduced into the cell and extends horizontally across the
compartment U immediately below the anode.
In the upper side of the pipe P are a number of apertures p. It is preferable to
have the pipe P extended and doubled or forked within the compartment U so that
the apertures p may be distributed over a large area. P is the feed pipe which
supplies the zone Z with fresh electrolyte in the manner indicated. The

page_text: apertures direct the incoming stream of electrolyte upon the lower limit of
the chlorine zone. This stream, though so gentle in its flow as to leave the
chlorine zone undisturbed, serves to keep the surface of the anode itself in
contact with enough fresh electrolyte to maintain the process uninterrupted. The
supply of electrolyte is introduced to the pipe P by the funnel at its outer end.
The pipe P, with its upward directing apertures, is adapted to the performance
of two functions. The anode is constantly washed by fresh electrolyte from the
apertures p, and the electrolyte zone is kept supplied. The arrangement shown
enables those two offices to be filled by one pipe P. Obviously, the apparatus
may be divided according to functions and two supply pipes used, one to keep
the anode in good contact with electrolyte, another to introduce the displacing
liquid.
The location and character of this supply pipe may vary with the solutions
treated by my process. The principal feature of this process is the adjustment
of flow in mass to progressive diffusion in an electrolytic column. The supply
pipe P is the source of the flow of mass, and is to be located and constructed
with a view to the peculiarities of the diffusion or diffusions to be offset, and also
with reference to the relative densities of successive strata of liquid in the
column.
For instance, if only one of the ions is soluble and diffusive, the location of the
supply pipe may be chosen with reference only to diffusion from one electrode
toward the other. If both ions are soluble and diffusive the supply of electrolyte
should be introduced to a middle ground between the electrodes, so that a flow in
both directions offsets the two diffusions.
In the electrolyses of common salt solution, if the electrolyte be warm, so
little chlorine is retained in solution that the supply of electrolyte may be
introduced anywhere in the cell, so long as the displacement flow be adjusted to
oppose the diffusion of caustic soda from the cathode, and the anode be kept in
contact with fresh electrolyte. The above described location of the feed pipe P;
with its apertures directed toward the anode has proved a good arrangement for
purposes of the process, although under proper conditions of temperature the
outlet of pipe P may be placed even above the anode, for the reasons just
expressed.
Another mode of supplying the upper zone with sodium chloride is to suspend a
basket of porous material in the electrolyte, filled with crystals of common salt.
By percolation through the basket salt is supplied to the solution near the anode.
This of course has no effect on the downward displacement of the lower zones,
and merely serves as an auxiliary precaution for keeping the anode in good contact
with fresh electrolyte.
A tube T connects the lower portion of the zone Z³ with the caustic soda zone NA
under the diaphragm. The tube T lies in the lowest portion of the compartment U
and extends throughout nearly the entire length of that compartment.
From the concentrated soda zone NA at the end of the compartment L most
remote from the lower end of the tube T (Fig. 1) passes the tube na. This tube
rises to a height corresponding to the desired level of the electrolyte in the
compartment Ŭ, when it turns in a siphon shaped delivery pipe.
It is now obvious from the intercommunication of the liquid above and below the
diaphragm, that as fast as a solution of common salt flows into the cell through the
apertures p, so fast will a concentrated solution of caustic soda flow from the delivery
end of the tube na in order to preserve the static balance of the liquids standing in
the electrolytic cell and in the tube na.
Observation of the behaviour of an electrolytic cell like the one described will
enable an operator so to adjust the quantity of inflow of electrolyte at P that the
rate of diffusion of caustic soda will be exactly balanced by the rate of supply of
electrolyte.
Observation of an apparatus in continuous operation has determined the rate of
flow necessary to balance exactly the upward diffusion of caustic soda. This is a

page_text: general downward movement of from ten to twelve inches in twenty-four hours.
The liquid between the electrodes is changed by this movement about once in six
hours.
The rate of flow depends on the circumstances under which the manufacturer
abors. If a plentiful supply of sodium chloride solution is at hand, and chlorine is the
product desired, the flow through the cell may be rapid. The efficiency of the
electric current under these conditions is nearly perfect. If on the other hand
power is plentiful and the double product is desired, the flow in the cell may be
reduced below the rate indicated above, and the distance between the electrodes
increased, and highly concentrated caustic soda obtained with a loss of electrical
energy.
The above described process of downward displacement includes within it a
sub-process by which a progressive concentration of the ion in solution below the
diaphragm is effected. That portion of the electrolytic apparatus having for its
function the progressive concentration of caustic soda consists of the tube T and the
cathode B, (Figs. 1 and 2) constructed and arranged as follows:
The tube T through which caustic soda is transferred from the diffused zone Z³
to the lower zone N A extends throughout nearly the whole length of the compart-
ment U, (Fig. 1) and lies at its lowermost portion where the inclined sides of the
diaphragm D converge.
The compartment L is divided transversely by a number of vertical partitions F
affixed to or integral with the cathode base B. The partitions F conform to the
desired shape and inclination of the diaphragm D which is supported by the
partitions Fat intervals throughout its length. The cells included between
the partitions F communicate with one another through apertures which collectively
form a central alley a.
The partitions F are at intervals extended up into the chamber H. These
extensions are at x¹¹ (Figs. 1, 2 and 2^).
The transfer tube T enters the end cell marked 1; the soda delivery pipe na
emerges from the end cell marked 2.
In the process of displacement already described diffuse caustic soda enters the
alley near the cell 1 and passes in slow current through the cells to the cell 2.
Meanwhile fresh caustic soda is being developed on the surface of the cathode B,
so that in its flow from cell 1 to cell 2 the caustic soda receives a succession of
increments of concentration and is withdrawn from that portion of the apparatus
where soda is most highly concentrated.
That end of the tube T where diffuse soda enters it should be placed, if possible,
at or near that portion of the diaphragm under which lies the cell containing the
most concentrated soda. At that point the soda coming through the diaphragm
will be densest and the tube T will withdraw from the zone Z³ the most concentrated
caustic soda present in solution above the diaphragm.
The location of the tube T of Fig. 1, causes a flow of diffuse soda from all parts
of the compartment U toward the entrance of the tube T. The flow in U is
parallel to the flow in L, so that as these parallel currents progress the liquid
above and below the diaphragm increases in concentration. Thus the diffusive
tendency is maintained nearly uniform along the entire length of the diaphragm.
To carry on a process of progressive concentration like that described above, it
has been found advisable always to employ a succession of cells similar to those
which divide the compartment L of Fig. 1, for otherwise the ebullition of the gases
of electro-chemical decomposition will stir the solution so that it will remain
uniformly concentrated throughout. The employment of cellular construction
confines this stirring to small spaces so that the general progression of concentration
is not interrupted.
.
This sub-process of progressive concentration may well be valuable in itself, and
be employed in electrolytic vessels wherein no diaphragm is used.
To avoid polarization by accumulation of gases at the electrodes of the apparatus
the electrodes themselves are made large and of irregular surface.
The cathode B

page_text: extends over the entire base of the apparatus, and inclines upwards from its middle
to two sides, (Fig. 2) or toward its centre (Fig. 4) according to the location and
shape of the chamber H. The desired irregularity in surface is secured by making
the partitions F, of the same material as the base B. The partitions F thus form
a series of deep corrugations upon the base B.
Hydrogen liberated at such an electrode easily disengages itself from the surface
and offers no impediment to the progress of the process.
The anode of this apparatus should be constructed, not only with a view to avoiding
polarization, but also to meet other requirements peculiar especially to processes of
electrolyses of chlorides. Like the cathode, the anode should have a large surface
to avoid polarization, and further, it should be of such material as to resist the
action of chlorine which, especially in its nascent state, attacks many substances
with avidity.
Of all known substances platinum fulfils the second requirement most completely;
but if the electrolytic cell is large, a platinum anode extensive enough to escape
polarization will be very costly. Gas carbon is cheap, resists the action of chlorine
and may be used successfully as material for an anode if kept in good electric
connection with the leading wires.
Under the influence of an electric current gas carbon slowly wastes away; unless
provision is made for this the contact with the leading wires is liable to be broken
and the current impeded or stopped. Gas carbon slabs cast in a lead plate have
been used heretofore for electrodes; but in an apparatus where chlorine is present
the contact between carbon and lead is soon broken by the formation of lead
chloride in the joints between lead and carbon. Contact between gas carbon and
almost any available metal, except platinum, will be interfered with by the action
of chlorine in the same way.
Gas carbon is hard and difficult to cut into any regular form, so that where it
may be used in rough lumps much expense is saved.
The electrode invented for use in connection with this process and apparatus
.overcomes the difficulties enumerated.
At the level in the electrolytic cell where the anode is to be secured a few
platinum wires W are stretched across the cell. These wires are connected with
the leading wires of the apparatus which lead to the contact. Upon these wires
lumps of gas carbon G are laid.
The weight of these carbon lumps keeps them in good electrical contact with
each other and with the supporting wires W. The surface of the electrode thus
constructed is, even in a small apparatus, whose cell is only four or five inches in
diameter, many square inches in extent, so that the resistance due to polarization
is reduced to a minimum. As the electric current wastes away the carbon lumps,
they settle on the wires and on each other. The contact cannot be broken, and the
distance between anode and cathode is preserved constant.
leading
The leading wires of such an anode must be large to be of low resistance.
A platinum leading wire of suitable size would be extremely costly;
wire used as a substitute for a platinum connection is constructed as follows:
A large copper wire C (Fig. 3) is encased in a close fitting lead tube J, which in
turn is enveloped in a hard rubber jacket, R.
At intervals along this insulated cable platinum pegs or screws S are driven
through rubber and lead to the copper. The platinum supporting wires W, may
be fastened to these pegs. Hard rubber is practically unaffected by chlorine; and
lead only slightly. The chance of any chlorine-laden solution penetrating to the
copper wire is therefore very small.
The only objection to the use of gas carbon is the discoloration of the liquids in
the cell consequent upon the presence of small organic particles which drop from the
carbon and come in contact with caustic soda. This circumstance is trivial in
snost cases, and does not affect many commercial uses of caustic soda. If a clear
liquid is desired, platinum anodes may be used.

page_text: In place of carbon lumps, magnetite serves well, as will any mineral conductor
not susceptible to the attacks of chlorine.
A form of electrolytic apparatus designed especially with a view to mechanical
convenience is shown in assemblage and detail in Figs. 4, 5, 6, 7, 8, and 9. In this
apparatus the various parts are grouped and attached so that all connections are
made through and to the cathode-base.
Fig. 4 shows a cylindrical electrolytic apparatus, in vertical section. In it the
relative location of the anode composed of carbons G, and platinum wires W, of the
feed pipe P with its apertures p, the diaphragm D inclined toward a gas-chamber H,
the cathode B, and the horizontal zones Z', Z, Z³ and N A, is the same as in the
apparatus of Figs. 1 and 2.
In the apparatus of Figs. 4 and 5, the hydrogen chamber H is internal instead
of external, the leading wire C, with its insulating jacket, and the pipe P, are
curved to conform to the cylindrical shape of the apparatus. The diaphragm D,
in conformity to the shape of the apparatus, is conical, and rises to the middle of
the apparatus, where it delivers gases to the chamber H.
Into the chamber H rises a continuation of the cathode-base, which may be
integral therewith, or another piece of the same material as the cathode. This
extension is shown in Figs. 4, 4, 5 and 9 as ³, containing radial cell walls ¹,
which correspond in function with the partitions a¹ of Figs. 1, 2, and 2ª. So also
the cathode B is composed of radial cells, intercommunicating through apertures in
the partitions. These apertures collectively form a winding alley corresponding in
function with the straight alley a of Fig. 2.
The bell H and its enclosed partitions are of any suitable non-corrodible
material. The enclosed cylindrical cell a is preferably of the same material as
the electrode on which it rests and of which it forms a continuation.
The transfer tube T of this cylindrical apparatus is a short internal trap-tube T,
shown in detail in Fig. 7, or a direct passage (as in Fig. 8) where there is provided
a substitute for the trap-bend of the tube in the shape of a plate or cup of inert
material such as porcelain or glass, situated immediately below the tube T. This
is shown at 5, in Fig. 8. In the tube T of Figs. 1 and 7, and on the cup 5 of Fig. 8,
no gases are developed, and none pass through the passage T into the upper chamber
of the apparatus.
The cell-wall nearest the passage T and its gas-trap 5, contains no aperture.
On the other side of this blank wall is the outlet pipe na. For the diffuse soda to
pass from T to na, it is necessary for it to traverse the entire surface of the cathode
by going around the circumference through the radial partitions. Thus the
progressive concentration of soda is effected.
The chief difference in construction (apart from general form) in this apparatus
as distinguished from the rectangular one, is that all the connections, for admission
of electricity or electrolyte and for withdrawal of products, are through the cathode
base B. The bell b which forms the walls of the compartment U can be removed
from the apparatus whose condition may be examined with a view to repairs or
cleaning without necessitating the uncoupling of complicated connecting pipes and
wires.
Furthermore, the bell b, may be of glass, and in one piece, so that leakage is
impossible, and observation of the process possible at all times.
Fig. 5 shows the radial cells in place, the concentric arrangement of the
leading wire and supply pipe, and the manner of stringing the supporting wires W.
Fig. 6 is a perspective view of the cellular cathode, without the central group of
cells which extends up into the chamber H. This central group is preferably made
in a separate piece, and is shown in Fig. 9.
Experience with various forms of apparatus involving the principles herein
described has shown that for usual purposes the electrolysis in a single cell occasions
a fall in electric pressure of about five volts.
Ordinarily, electric current is furnished at pressures much greater than five volts,
so that to employ electro-chemical cells in parallel electric connection would result
B

page_text: in enormous waste in the generation of electricity, and would involve great expense.
in providing conductors of sufficient size and suitable construction. It will be
found necessary in most instances, to multiply the number of electro-chemical
cells in proportion to the electric pressure supplied, and to connect them in series.
Fig. 10 shows a battery of electrolytic cells connected in electric series, with
accessory apparatus.
The nature of the electro-chemical process to be carried on renders necessary a
substantially continuous supply of sodium chloride. This supply should be of
uniform concentration in all the cells of a battery and should for convenience be
drawn from one common source. But, were unbroken streams of electrolyte to flow
from this common source to all the cells, short-circuiting of the electric current
through the liquid would result, involving an appreciable loss of electric energy.
To avoid this, and at the same time to secure the regular supply of electrolyte
necessary to smooth continuity of the process, provision is made for a regularly
intermittent supply of electrolyte, in uniformly measured portions furnished in
broken streams from the common source of supply.
In Fig. 1 there is shown in detail a contrivance for effecting this purpose.
On a shaft M, is secured a tubular arm N open at both ends, bent so that part
of its length lies along the shaft M, then bent so as to extend out at right angles
to the shaft, gradually bending from a radial to a circumferential direction so as to
form a sickle-shaped scoop.
As the shaft M revolves this radial scoop N turns in the direction indicated by
the arrow.
The sector-part of the scoop N dips beneath the surface of the electrolyte supply
in the tank Y, situated under the shaft M. This supply is kept at constant level
by a float valve Q (Fig. 10). The funnel E, leading to the supply pipe P, is placed
under the shaft-outlet of the scoop tube N; as the shaft M revolves, the open
scoop-tube spills the solution dipped up by its sector-part into the funnel E leading
to the pipe P. This contrivance is multiplied to correspond with the number of
cells in the battery, as illustrated in Fig. 10. By this means short circuiting
through the supply tank is prevented, and an invariable supply of electrolyte
secured.
The level of supply in the tank Y is regulated by the ball valve Q, in Fig. 10.
Similar precautions should be taken with the delivery tubes na; were a number
of them to dip into a common trough or tank, short-circuiting would result.
The product of electrolysis should be made to drip intermittently from the
tubes na.
Should the flow be so copious as to deliver unbroken streams instead of
successive drops, the ends of the tubes na may be dipped in petroleum oil V floating
on the surface of the main discharge pipe X, Fig. 1. Drops of caustic soda
emerging from the tubes na into petroleum oil will be much larger than drops
formed in air. Petroleum oil does not offer sufficient conductivity to permit short
circuiting of the battery of cells, and serves the further purpose of keeping the
outcoming caustic soda from contact with the air and the carbonic dioxide present
in the air.
In Fig. 10, the chlorine pipes cl are shown as led to a main pipe which conducts
the chlorine to a chamber filled with unslaked lime, where bleaching powder may
be produced. The bydrogen is collected in a gas-holder to be used as fuel or as an
illuminating agent.
Caustic soda is withdrawn to an evaporator, where the small amount of sodium
chloride still in solution is crystallized out. The sodium chloride remaining after
a slight evaporation of the solution will amount to no more than five per cent. of
the aggregate weight of sodium chloride and sodium hydrate in solution.
The above described displacement process of electrolysis when supplied to the
decomposition of a solution of common salt results only in a downward displacement
of gravitating products. The displacement method is applicable to the treatment
of substances of various specific gravity in such a way as to cause upward flow, as
well as downward flow, or both simultaneously. To illustrate the adaptability of

page_text: rises to the top of the electrolytic cell, and conects above the anode. symbolically
represented these attendant reactions are as follows:
Na2+ water = 2 (NAOH) + 2 H.
SO + water = H2SO4.
So that here, as in the electrolysis of common salt, the elementary ions immediately
form new combinations which are the ions practically available.
Fig. 11 represents an apparatus for electrolysis of sodium sulphate.
This apparatus does not differ in principle of construction from the one shown in
Figs. 1 and 2, except for the internal arrangement of the chamber H, and the
absence of the cells in the cathode.
the
The diaphragm D separates the cell into an upper compartment U and a lower
compartment L. The inclined surface of the diaphragm D guides hydrogen
liberated at the cathode into a chamber H whence it is conducted through a tube h.
The iron cathode B and the platinum anode W with its gas-carbons, occupy
same relative situation in the apparatus of Fig. 11, as do the electrodes of Figs. 1
and 2.. A tube T communicates between the chambers U and L, a pipe na forms
an outlet from the compartment L. A feed pipe P enters the cell between the
electrodes and is similar in construction to the pipe P of Figs. 1 and 2.
Upon the application of the electric current and the consequent formation of
ions, the various substances in solution arrange themselves in the order of their
specific gravity. Under the diaphragm in the zone N A collects concentrated caustic
soda. Immediately above the diaphragm there-forms a zone Z of diffuse caustic
soda. Between the zone Z' and the anode W lies the zone Z³ of undecomposed
electrolyte sodium sulphate. Uppermost in the liquids is the zone Z¹ containing
dilute sulphuric acid. Above the liquid in the cell oxygen collects in the space O,
to be drawn off through the tube o.
The reuniting of the ions in solution by diffusion is prevented in this apparatus
by the inflow of fresh electrolyte through the pipe P. This pipe delivers the
solution of sodium sulphate to the zone Z; the incoming sodium sulphate displaces
the sulphuric acid above it. The acid is drawn off through the tube I. The rise
of the level of the liquids in the upper portion of the cell overbalances the sodium
hydrate in the pipe na so that the sodium hydrate is displaced downward and the
sulphuric acid displaced upward by the entrance of sodium sulphate to the
electrolytic cell at the zone Z'.
The operation of the apparatus hereinbefore described involves another invention
which as an auxiliary method assists the apparatus in performing the main process
of electrolysis in which the substances in solution in the electrolytic cell are
maintained in the superimposed zones.
The iron cathode-base of the apparatus described is of relatively high heat-
conductivity when compared with the glass or slate sides of the enclosing vessel.
The passage of the electric current, by reason of the internal resistance of the
liquid, warms the apparatus. The heat of the apparatus is conveyed away by
conduction and radiation much more rapidly at the iron cathode-base than at the
sides of the apparatus. Consequently the lower strata or zones of liquid will be
kept cooler than the upper zones, and thus the diversity of their respective specific
gravities will be exaggerated. By this means the tendency of the extreme zones

page_text: to remain widely separated from each other is materially assisted, and an additional
safeguard to the proper performance of the main process afforded.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, I declare that what
I claim is:
1. An electro-chemical process which consists of displacing an ion in solution in
an electrolyte by supplying the electrolyte to the electrolytic cell, and withdrawing
the displaced ion from the electrolytic cell; such supply of the electrolyte and
withdrawal of the ion being at a rate corresponding substantially to the rate of
diffusion of the ion from its electrode through the electrolyte toward the opposite
electrode.
2. An electro-chemical process which consists of displacing an ion in solution in
an electrolyte by supplying the electrolyte to the electrolytic cell and withdrawing
from the electrolytic cell the ion thus displaced; such supply of the electrolyte
and withdrawal of the ion being at a rate equal to or greater than the rate of
diffusion of the ion from its electrode through the electrolyte toward the opposite
electrode said displacement being in a direction substantially opposite to the
direction of said diffusion.
3. An electro-chemical process which consists of displacing an ion of superior
specific gravity by supplying the electrolyte to the electrolytic cell, and withdrawing
the displaced ion from the electrolytic cell; such supply of the electrolyte and
withdrawal of the ion being at a rate corresponding substantially to the rate of
diffusion of the ion through the electrolyte toward the opposite electrode.
4. An electro-chemical process which consists in maintaining within the
electrolytic cell a zone of undecomposed electrolyte interposed between the ions at
the electrodes by supplying to such zone fresh quantities of the electrolyte, thereby
displacing the ions toward appropriate electrodes, and by withdrawing from the
electrolytic cell the ions thus displaced; the supply of the electrolyte and the
withdrawal of the ion being made to proceed at such a rate as to maintain the zone
of undecomposed electrolyte between the ions substantially constant in volume.
5. An electro-chemical process of producing sodium hydrate and chlorine from a
solution of sodium chloride which consists of maintaining within the electrolytic
cell a zone of undecomposed solution of sodium chloride interposed between the
sodium hydrate and chlorine at their respective electrodes by supplying to such
zone fresh quantities of sodium chloride solution so as to displace the sodium
hydrate toward its appropriate electrode and by withdrawing from the cell the
sodium hydrate thus displaced; the supply of sodium chloride solution and the
withdrawal of sodium hydrate being made to proceed at such a rate as to
maintain the zone of undecomposed sodium chloride between the ions substantially
constant in volume.
6. A process of progressive concentration of an ion in solution in an electrolytic
cell, which consists of conducting the ion from that region in the electrolytic
cell where it is diffuse; and passing it across the surface of the electrode where
the ion is being liberated, thus giving the diffuse ion, in its passage, successive
increments of concentration from the electrode, and withdrawing from the electro-
lytic cell the ion thus laden with increments of concentration after its passage
across the electrode.
7. A process of progressive concentration of an ion, which consists of displacing
the diffused ion by introducing fresh electrolyte to that region into which the iou
tends to diffuse, conducting the diffused ion thus displaced from that point in the
said region where it is most concentrated to the electrode at which the ion
originates, and there passing the ion across the surface of the said electrode where
constant increments of concentration are being supplied, and finally discharging
the ion laden with increments of concentration after its passage across the
electrode.
8. A process of progressive concentration of the solution of sodium hydrate

page_text: 5
obtained from electrolysis of a solution of sodium chloride which consists in
displacing the diffused sodium hydrate by introducing a supply of sodium chloride.
into that region in the electrolytic cell into which sodium hydrate tends to diffuse
from the cathode, conducting the diffused sodium hydrate thus displaced by the
fresh supply of sodium chloride from the point in the said region where the sodium
hydrate is most concentrated to the cathode where sodium hydrate originates, and
there passing the diffused sodium hydrate across the surface of the cathode, where
constant increments of sodium hydrate are added to the solution, and discharging
the sodium hydrate solution after it has received increments of concentration in its
passage across the cathode.
9. An electrolytic apparatus containing in combination with horizontal elec-
trodes, a diaphragm located between the electrodes and separating the electrolytic
cell into compartiments, a supply inlet to one compartment, a passage between the
compartments, and a discharge outlet from the other compartment, substantially as
and for the purpose described.
10. In an electrolytic apparatus the combination of electrodes situated in
diaphragm-separated compartments, a supply inlet to one compartment, a discharge
outlet from the other compartment, and a passage between the compartments,
substantially as and for the purpose set forth.
11. In an electrolytic apparatus the combination of electrodes situated in
diaphragm-separated compartments, a supply inlet to one compartment, a discharge
outlet from the other compartment, a passage between the compartments and a gas-
chamber, so situated as to receive the gases arising in the lower compartment,.
substantially as and for the purpose set forth.
12. In an electrolytic apparatus, the combination of compartments separated by
a porous diaphragm, a gravity contact electrode situated in one compartment, a
supply pipe for electrolyte, entering the apparatus on one side of the diaphragm, a
discharge pipe from the apparatus on the other side of the diaphragm, a passage
between the compartments, and a gas chamber, so situated as to receive the gases
arising in the lower compartment, substantially as and for the purposes set forth.
13. In an electrolytic apparatus, the combination of compartments separated by
a porous silicious diaphragm, an electrode of carbon in gravity contact with
platinum wires situated in one compartiment, a supply pipe for electrolyte on one
side of the diaphragm, a discharge pipe on the other side of the diaphragm, a
passage between the compartments and a gas chamber, so situated as to receive
the gases arising in the lower compartment, substantially as and for the purpose
set forth.
14. In an electrolytic apparatus, the combination of an inclined diaphragm
supported by a corrugated electrode, and a gas chamber at the uppermost part of
the inclined diaphragm, substantially as and for the purpose set forth.
15. In an electrolytic apparatus, the combination of a concavo-convex porous
diaphragm supported by a corrugated electrode, and a gas-chamber, situated at the
highest point in the diaphragm, substantially as and for the purposes set forth.
16. In an electrolytic apparatus, an electrode containing a series of connecting
chambers, a supply inlet to one end of the series, and a discharge outlet from the
other end thereof, substantially as described.
17. The combination in a containing vessel composed of separable parts, of
electrodes, leading wires, a supply pipe for electrolyte, and outlets for electrolytic
products all of whose connections are made through one of the separable parts of
the containing vessel, substantially as and for the purpose set forth.
18. The combination, in a containing vessel having a separable base, of
electrodes, leading wires, a supply pipe for electrolyte, and outlets for products of
electrolysis, all of whose connections pass through the separable base, substantially
as and for the purpose set forth.
19. An electrolytic apparatus whose cathode is the base of the apparatus, and in
which the leading wire. of the anode, the supply pipe for electrolyte and the

page_text: .
discharge pipes for the products of the electrolysis pass through the cathode-base,
substantially as described.
20. In an electrolytic apparatus the combination of electrodes, diaphragm
separated compartments and a conduit from one compartment to the other
provided with a gas-trap, substantially as and for the purpose set forth.
21. In an electrolytic apparatus, a containing case, electrodes situated in
diaphragm separated compartments, the diaphragm, a
passage between the
compartments, a supply inlet to one compartment, a series of connecting chambers
in the other compartment, a supply inlet for said series arranged at one end thereof,
and a discharge outlet for said compartment and series located at the other end of
the series, substantially as described.
22. An electrode which consists of two systems: first, an internal system of
corrodible conductors surrounded and insulated by non-corrodible material; second,
an external system of uninsulated non-corrodible conductors, the internal and
external systems being connected electrically by non-corrodible metallic pins which
pass through the insulation of the internal system in such a manner as to exclude
all corrosive agents from the internal system while maintaining and preserving
good electrical contact with the external system.
23. A leading-in wire composed of a copper conductor enveloped in a hard
rubber jacket, and platinum pins which pass through the rubber jacket to the
copper, establishing electrical contact with the latter, the ends of the platinum pins
which project out of the rubber being adapted to the attachment of electrical
connections with an electrode.
24. The combination, with an insulating leading-in wire, of metallic conductors
which pierce the insulation and make contact with the leading-in wire, and an
electrode consisting of non-metallic conducting pieces in gravity-contact with
metallic conductors, the latter attached to the metallic conducting points which
pierce the insulation of the leading-in wire.
25. The method of constructing a porous diaphragm, which consists in filling a
re-enforcing frame work with Portland cement or its equivalent, and moulding the
framework thus filled, while plastic, into the shape desired.
26. A diaphragm of porous Portland cement, or its equivalent, re-enforced by
fibrous or textile material, the fibrous or textile material being filled and protected
by the cement.
27. A diaphragm of porous Portland cement or its equivalent, re-enforced by
asbestos fibres, substantially as herein described.
28. The method of creating and maintaining a diversity in specific gravity
between the strata of an electrolyte, which consists in keeping the lower portion of
the electrolyte at a temperature lower than that of the upper portion.
29. The method of creating and maintaining a diversity in specific gravity
between the upper and lower strata of an electrolyte, which consists in permitting
the heat of internal resistance of the electrolyte to radiate from the electrolyte
more freely at the lower strata than at the upper strata.
30. In an electrolytic apparatus, a base of high heat-conductivity and an upper
portion of relatively low heat-conductivity, substantially as set forth.
Dated this Twenty-second day of March 1894.
HENRY CARMICHAEL,
Glenwood Street, Malden, Massachusetts.
Alfred G. Brookes,
55 & 56, Chancery Lane, London, W.C., Agent for the Applicant.