Improvements relating to the Production of Soda and Chlorine, and to Apparatus therefor.
Year: 1892

page_text: Date of Application, 2nd Jan., 1892-Accepted, 2nd July, 1892
COMPLETE SPECIFICATION.
[Communicated from abroad by ELISHA BARTON CUTTEN, 29, Broadway, of the
City, County, and State of New York, United States of America, Chemist.]
Improvements relating to the Production of Soda and Chlorine, and
to Apparatus therefor.
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 :-
The invention is a new method of and apparatus for electrolytically producing
soda and chlorine.
It is well known that common salt, sodium chloride, (NaCl) can be electrolytically
decomposed in its aqueous solution; chlorine, (Cl) being liberated at the anode,
and sodium, (Na) at the cathode; and that thereupon, by reason of the decom-
position of the water, caustic soda, sodium hydrate, (NaHO) is produced.
The principal obstacles to the successful separation of chlorine and soda by this
means, are, first, the production of chlorinated soda (CINAHO) by the combination
of the chlorine and caustic soda in the cell, which, being a less stable compound
than the sodium chloride, uselessly absorbs the electrical energy for its decom-
position; and second, the weakening of the electrolyte due to the liberation of the
solvent (water) at the surface of the anode, which in turn becomes decomposed at
the expense of the current.
I have discovered that these, as well as other difficulties well known in the
operation, can be obviated by the new method hereinafter described, the principle
of which is two-fold and is as follows;―
To cause that part of the solution which, as the electrolytic process proceeds,
becomes most heavily charged with soda, to become separated from the remainder
of the solution.
To reduce or prevent the possibilities of any combination of the chlorine and
soda by mechanically removing the chlorine from the solution.
The consequence is, first, the production of a very dense salt soda solution, from
which the soda can be obtained by simple evaporation, and second, the separation
of the chlorine in gaseous form. This chlorine I subsequently utilize.
In the accompanying drawings,
Fig. 1 illustrates an electrolytic cell of well-known construction, but which is
open to all the objections which my invention obviates; and said cell is here
introduced for purposes of comparison only.
3
Fig. 2 is a vertical transverse section of a simple form of my improved cell.
Fig. 3 is a similar section of the same cell containing salt or other comminuted
material.
Fig. 4 shows in vertical section an improved form of my said cell.
Fig. 5 shows the said cell with its appurtenances as arranged for practical use, and
Figs. 6 to 9 illustrate my invention arranged commercially and on a large scale;
Fig. 6 being a vertical transverse section, Fig. 7 an end elevation, Fig. 8
longitudinal vertical mid-section, and Fig. a plan partly in horizontal section.
Similar letters of reference indicate like parts.
Referring first to Fig. 1, A is an iron vessel. B is a porous cup of unglazed
earthenware therein. Cis an anode of carbon which is supported in the cover D.
G is a battery, one terminal of which is connected to the anode C, and the other
o the vessel A, which forms a cathode. E is a pipe leading from the cover D to
he porous cell. The vessels A and B are filled with a solution of sodium chloride.
When electrolysis ensues, sodium is produced at the cathode, and chlorine at the

page_text: anode. The sodium combines with hydrogen from the water to make caustic soda;
and the strongest part of the solution sinks to the bottom of the cell, as indicated
by the more closely shaded lines in the drawing. The chlorine produced at the
anode C escapes at the pipe E.
It will be observed that the porous cup B is relied upon to separate the soda
and the chlorine; otherwise, there will be a combination of these two substances to
make chlorinated soda. The inefficiency of the device will be quite apparent from
the drawing, as there is direct communication shown between the contents of the
porous cup and the strong soda solution at the bottom. There is also nothing to
prevent the porous cup from being attacked and disintegrated, which very speedily
occurs. The only mode of obtaining the chlorine is by allowing it to bubble to
the top of the solution in the vessel B, and so to escape through the pipe E.
Practical experience with cells of this kind has shown to me that although the
operation of electrolysis begins fairly well, and while the soda solution is very
weak may appear to continue satisfactorily, yet, as soon as the soda of the solution
becomes strong enough to render its concentration commercially profitable,
electrolytic decomposition becomes gradually less perfect, until finally the
generation of chlorine and caustic soda ceases altogether despite that the energy of
the current supply does not apparently become any less. The consequence is a
total waste, and the cell is, of course, inefficient and useless.
I will now describe my new form of apparatus in which all the difficulties of the
cell shown in Fig. 1 are fully overcome. In Figs. 2 and 3, A is an iron containing
vessel to which one terminal of the battery G is attached, so that said vessel forms
the cathode. B is a porous cup of earthenware or like material. C is the anode,
connected to the other terminal of battery G and preferably made of gas carbon.
The anode C is received in a block F also of gas carbon, which is surrounded with
insulating material 6 and placed in the bottom of the porous cup B, so that it
projects upward in said cup, as shown.
is
The cup B is porous only over its middle portion d; above and below this part,
as at c and e, it is glazed and non-porous. The glazed portion at the lower part of
the cup resists the disintegrating effect of the soda solution. Considerable space
left between the cup B and the bottom of the vessel A. for the accumulation of the
soda solution, which will thus be out of contact with the cup B. The upper part of
the inner side of the vessel A is covered with varnish or other insulating material f.
The production of soda is thus limited to the cathode surface below this coating,
the object being to render the upper portion of the salt solution in the vessel A as
free as possible from soda.
The bottom of the vessel A is funnel-shaped, and is provided with a faucet a for
convenience in drawing off the solution.
The top of the cup B is completely closed by a cover D, into which opens a
tube which communicates with any suitable form of pump, exhauster or suction
apparatus. The faucet g controls the inflow to vessel A of the salt solution to be
electrolyzed, which may be led from any suitable reservoir.
I will first describe the operation of the process as carried out in the cell
illustrated in Fig. 2. The entire cell is filled with the salt solution. The pump
in communication with pipe E is operated until the level of the liquid in cup B is
from one-half an inch to an inch above that of the liquid in vessel A. The
current is then established. The chlorine formed at the anode C, (or a very large
percentage of it), is mechanically drawn out of the liquid by the action of the
pump and through the tube E to any suitable reservoir. Whatever chlorine may
remain in the solution appears in the form of ascending bubbles close to the anode,
while practically none is found at the wall of the porous cup. The change of
color of the solution is, as the chlorine is drawn out of it, quite manifest.
Meanwhile, in the vessel A, soda is formed and bydrogen is liberated, the latter,
if unobstructed, rising along the wall of the vessel and escaping at the top. The
soda descends along the wall, as shown by the arrows, most of it going to the
bottom of the cell to form a strong soda solution, (indicated by the more heavily

page_text: shaded part in the drawing), and, of course, some mixing with the salt solution.
It will be observed, however, that the dense soda solution is below the bottom of
the porous cup, and that it goes to the bottom of the cell by its own gravity. The
curved dotted line in Fig. 2 indicates somewhat approximately the proportion of
soda becoming diffused in the solution in proportion to the vertical height of the
latter above the bottom of the cell.
It will be apparent from the preceding that toward the bottom of the cup B
where the chlorine solution on the interior is weakest, the soda solution on the
exterior is strongest; while toward the top of the vessel A where the soda solution
on the exterior of the cup B is weakest, the chlorine solution within said cup is the
strongest. It will be apparent also that wherever either solution comes in contact
with the porous part of cup B, it is very weak. It will thus be seen that even
without the use of the suction apparatus for removing the chlorine, the arrangement
of the cell is such that the soda solution tends to separate itself from the chlorine
solution by the action of gravity; and when it is so separated, it is not in a position
to be strongly acted upon by the chlorine solution, but, as has been described, in
addition to the self-separation by gravity of the soda, I provide for the mechanical
abstraction of the chlorine from the solution; so that the soda is prevented from
attack by the chlorine in two ways; first, as a consequence of its own gravitation
to a place where the chlorine cannot easily get to it, and second, by removing the
chlorine mechanically as fast as it is generated.
I find that these results are abundantly shown to be true by practical trials of
the cell.
I have stated that in Fig. 2 the electrolyte is renewed from the faucet g leading
to a suitable reservoir. I find it better in practice to use the arrangement shown
in Fig. 3, in which salt is directly packed in both the outer vessel and in the porous
cup, as shown at H and I. In this case, the soda solution, drawn off at the bottom
through the faucet a, is much stronger than before; while that in the upper part
of the vessel, especially such as is in contact with the porous wall d, is much
weaker. At the same time, waste of power, due to the generation of oxygen in the
cup B and the disadvantages incident to the drawing off of oxygen mixed with the
chlorine from said vessel, are avoided. Almost all the caustic soda, as it is
generated, percolates down against the outer wall of the outer vessel, while the
chlorine following the anode C goes directly upward.
While the form of cell illustrated in Figs. 2 and 3 is perfectly operative and
useful, it is none the less true that its porous partition interposes resistance in the
circuit, and is subject in time to disintegration.
In Fig. 4 I illustrate a form of electrolytic cell in which these difficulties are
obviated. Here, the porous cup B is wholly removed and in place thereof there is
substituted a vessel J, open at the bottom and preferably made of glass. It is
supported in any suitable manner; as, for example, by arms or brackets h
projecting inwardly from the top of the outer vessel A, upon which brackets a
flange on the inner cylinder J rests, as shown. The anode C is supported in any
suitable sleeve of insulating material which extends through the cover D' of the
vessel J; and said anode extends, as shown in the drawing, downward, somewhat
below the bottom of the cylinder J. The body of the vessel A is filled with salt,
as shown at H.
I have found, however, that even when salt is not used, no perceptible quantity
of hydrogen is drawn into the cylinder J even under a suction much more powerful
than that which meets all the requirements of the process; hence there is no waste
of power due to the generation of the hydro-chloric acid due to the union of
hydrogen with the chlorine. When the body of salt H is not employed, the
anode C may be made shorter; not extending below the lower edge of the
cylinder J. I find that it is advantageous tc introduce a current of saturated salt
solution upwardly along the surface of the anode. To this end. I cause a delivery
of salt solution from any suitable reservoir through the faucet gl to a tank K³.
From the tank K' extends a pipe which opens into the vessel A at K. The salt

page_text: solution then rises up from the pipe K, as indicated by the arrows in Fig. 4. Near
the bottom of the vessel A is a plate or partition L preferably of glass, which
causes the descending soda solution to pass outwardly away from the anode, and
also serves to intercept any bubbles of hydrogen which may be liberated from the
bottom of the tank and prevent their ascent into the cylinder J. The insulating
coating may be omitted in this form of cell, if desired, but it is best to provide
it in order to prevent the generation of soda in the upper part of the outer vessel.
It will be observed that in this form of cell, the separation of the soda solution is
effected by gravity alone; and that the difficulties incident to the use of a porous
cup are avoided.
Referring now to Fig. 5, it will be observed that the outer vessel A, the inner
cylinder J and the cover D' are substantially the same in construction as has
already been described in connection with Fig. 4. The anode C of carbon, how-
ever, instead of extending downward into the cylinder J, extends upward. It is
inserted in a block of carbon F, which is surrounded by insulating material b, and
this rests upon the glass partition L, which is supported in any suitable way within
the vessel A.
It will be noticed that a flat plate L is here substituted for the conical plate L
of Fig. 4. One terminal of the battery is connected, in any suitable way, to the
block F, and the other, as before to the vessel A. I have, in this figure, shown a
mass of solid salt I, surrounding the anode within the cylinder J, in addition to the
mass of salt H in the vessel; the two masses becoming practically one in the
lower portion of the vessel A below the cylinder J. In order to conveniently
introduce the salt into the cylinder J from time to time in order to strengthen the
solution as it becomes weakened at the anode, I arrange above the cover D¹a
hopper M having a removable cover which is to be kept filled with salt. In the
bottom of the hopper I provide a movable slide. By withdrawing this slide, the
salt may be caused to descend through the cover D' and into the cylinder J, so
that it is not necessary to open the top of said cylinder; and in this way, any
loss of chlorine gas and also the introduction of atmospheric air into the cylinder J,
is prevented. The slide is to be ground to a close fit or to be packed in any
suitable way.
I will now describe the various accessories which it is desirable to employ with
the electrolytic tank. To supply strong salt solution in place of that which is
weakened at the anode, a pipe opening into the cell at K leads from the supply
vessel K¹. The result is an upward circulation through the cylinder J. The
weakened liquid adjacent to the anode, being of reduced specific gravity, also rises,
and this weak liquor is drawn off by a pipe N which opens into the cylinder J and
communicates with a vessel N', in which the level is maintained nearly the same
as that in the outer vessel J. The overflow from this cup discharges into a tank O
from which it is lifted by a pump P through a pipe i, and is finally discharged into
a tank Qin which a mass of salt is placed. This body of salt rests upon a per-
forated false bottom in the tank Q. The weakened liquor, in percolating down
through the mass of salt in vessel Q, is re-fortified, and it finally passes through
an outflow pipe communicating with the bottom of vessel Q, as shown in the
drawing, below the perforated false bottom, whence it is discharged into a second
fortifying vessel Q', similarly constructed to vessel Q, through the body of salt
in which it percolates, and finally is discharged through a pipe leading to the
faucet g. The valve of faucet g' is controlled by levers operated by a float n¹ in
accordance with a well-known construction for controllable valves of this kind,
which float rests upon the solution in the vessel K'.
It will be seen from the foregoing that I have provided means for continuous
circulation. The strong salt solution entering the vessel A at the point K, rises
through the mass of salt I and through the liquor in the cylinder J, and becoming
weakened through the process of electrolysis, passes from the vessel J by the pipe N
to the receptacle N', then flowing over into the receptacle O, it is pumped through
the pipe to the vessel and so to the vessel Q', in passing through which vessels

page_text: t becomes re-charged with salt, and finally from the vessel Q¹ back through the
ipe and faucet g' to the receptacle K. The float n¹ of course regulates the
low as may be desired, the valve opening in the usual way, when the liquid in
eceptacle K becomes sufficiently lowered to allow the float to descend and so
open the valve. By this means the electric decomposition of water freed from the
solution by the decomposition of its dissolved salt is practically prevented.
In connection with the receptacle Q', I arrange a short stand-pipe O', in which
the strengthened liquor may accumulate when the valve g¹ is closed. Instead of
discharging the strong salt soda solution which, as already described, descends by
its own gravity to the bottom of the vessel A and beneath the partition L through.
a cock or valve a, as shown in Fig. 2, it may be discharged through a stand pipej
into a cup j', and thence be allowed to drip or trickle from a faucet (the stream
being thus sub-divided into drops for the purpose of electrical insulation) into a
receiving funnel k which communicates with a pipe 1, which leads into the receiving
tank R for the dense solution. The chlorine which is removed through the pipe E
by the action of the pump S may be conducted to any suitable receptacle or utilized
as may be desired.
In order to start the apparatus, I provide above the vessel Q a cock p' for the
delivery therein of brine. The masses of salt H and I placed in the cell, serve
both to keep up the strength of the solution and also to prevent diffusion of the
generated soda toward the anode, and to facilitate its gravitation to the bottom
of the cell. In place of such salt I may substitute any comminuted substance
which will not be attacked by the solution; this comminuted substance acting
simply mechanically in the manner and for the purpose already stated.
Referring now to Figs. 6 to 9 inclusive, the outer vessel A is of iron, stiffened
at the top by an angle iron frame 1, and by the bottom bars n and having trans-
verse struts pp". On these struts the glazed plate L is supported, being kept in
place at its sides by washers ¹. On this plate is placed a glass or earthenware
trough T, within which extends the carbon bar F, with an intervening coating of
The bar F is of moulded carbon and extends
insulation surrounding the bar.
nearly the entire length of the tank, its insulation being protected from the action
of the soda solution by the trough T. The anode consists of carbon rods C C
screwed or driven into holes in the bar F and projecting upwardly to a suitable
height. Near the rear end of the tank the bar is kept in position laterally by
guiding rods 99, while at the front end of the tank it passes through the wall
thereof, a stuffing box » being provided to prevent leakage around it. The carbon
bar F projects beyond its insulating trough T, and electrical connection is made
with it through a metal clamp 8, to which is attached a copper or other metal bar t
leading from the cathode connection of the next tank in the series. Such cathode
connection is shown at n² consisting of a metal bracket rivetted to the end of the
tank A and having fastened to it the copper conducting bar t¹ which leads to
the anode connection of the next tank beyond. Thus the electrical connections
are conveniently made at the front ends of the tanks, which are arranged side
by side in a row or gang. In case any tank requires repairing or cleaning, it
may be easily cut out of circuit by bridging over and breaking the connections.
The inner vessel or bell J is made in one piece, preferably of moulded glass
formed with an external rib ² resting on supporting brackets h, h, applied within
the tank at intervals. To enable salt to be readily introduced into the inner
vessel to supply the place of that consumed by the electrolysis, I provide the top
0 of the bell with one or more covered openings J¹.
The chlorine outlet-opening u is preferably at the rear end of the bell, and is
joined by an elbow u' of glass, porcelain or lead, to a branch-pipe u³ containing a
stop-cock or chlorine outlet valve u³. The branch-pipes from the several tanks
lead into the main suction-pipe E³, which communicates with the suction pump.
5 In case it is necessary to introduce salt to any tank, its valve u³ is first closed, or
in case its bell J is to be removed this valve is first closed, and then the elbow u¹
disconnected, whereupon the bell may be lifted out.

page_text: In this tank provision is made for collecting and removing the hydrogen which
bubbles up in the outer vessel. To this end, a hood U, which may be made of
sheet metal, is provided to fit into the space between the outer and inner
vessels, its flanges dipping beneath the liquid level to seal it. The hydrogen is
caught in this hood and is drawn off therefrom through a pipe and valve vl
into a main hydrogen pipe V leading to the exhaust blower or other suction
pump or pumping device by which the hydrogen gas is either fed to the
furnaces or is utilized in any suitable manner. This arrangement not only
saves and utilizes the hydrogen which is of some value, but also avoids risk of
explosion by the formation of an explosive mixture of hydrogen and air in the
tank house. In case it is necessary to disconnect or remove any tank, or to
take off its hood U, the hydrogen valve should be first closed and the com-
municating pipe v disconnected.
Beneath the glass plate L the tank slopes to a gutter w for leading off the
strongest soda solution; the latter being drawn equally from all parts of the
length of the tank by having to pass first through a plate w', which is perforated
at intervals with fine holes. From the gutter w at the front end of the tank,
the pipe leads to the discharge faucet, which drips or trickles the resulting
stream of soda solution into the tank pipe k, from which it runs off through the
soda main k¹.
The supply of strong salt solution to the tank, is admitted from a main g¹ by
a cock g and perforated nozzle, from which it drips into the tank or hopper K
and runs through a pipe K which communicates with the end of the carbon
bar F, which is bored or moulded with a duct y extending through it longitudinally
and having branch ducts y' formed in it vertically between the successive carbon
rods CC, as clearly shown in dotted lines in Fig. 8. The liquid passes up in
This con-
jets from these branches and flows upward between the anode rods.
struction is advantageous because it ensures a thorough distribution of the liquid,
introducing it at the points where is most effective.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, as communicated to me
by my foreign correspondent I declare that what I claim is :-
1. The process of obtaining caustic soda by electrolyzing a solution of sodium
chloride and causing that part of the solution containing the greatest proportion
of soda to become segregated or separated by the action of gravity upon it, or
by mechanical means, from the remainder of the electrolyte, and simultaneously
extracting mechanically from said electrolyte the produced chlorine.
2. An electrolytic apparatus operating and arranged substantially as herein set
forth, wherein a solution of sodium chloride may be electrolyzed to produce
caustic soda and chlorine in accordance with the process described.
3. An electrolytic apparatus operating and arranged substantially as herein set
forth, wherein a regulated continuous supply of sodium chloride may be electro-
lyzed to produce caustic soda and chlorine, and wherein the solution weakened
by electrolytic decomposition may be re-fortified with salt and returned to the
electrolytic cell for renewed decomposition in accordance with the process described.
4. An electrolytic cell having an outer vessel forming a cathode, a non-porous
inner cylinder open at the bottom and closed above, and containing an anode
and suction or pumping apparatus connected with the inner cylinder cover above
the liquid level and operating to exhaust gas from said inner cylinder; the whole
being adapted to the electrolysis of sodium chloride to produce caustic soda and
chlorine in accordance with the process described.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, Agents for the Applicant.