Process of and Apparatus for Dissociating Soluble Salts by Electrolysis.
Year: 1894

page_text: Date of Application, 18th Dec., 1894-Accepted, 19th Jan., 1895
Process of and Apparatus for Dissociating Soluble Salts by
Electrolysis.
I, HENRY SPENCER BLACKMORE, of Mount Vernon, in the County of West-
chester, State of New York, United States of America, Chemist and Metallurgist,
do hereby declare the nature of this invention and in what manner the same
is to be performed to be particularly described and ascertained in and by the
following statement :-
This invention relates to a process of and apparatus for dissociating liquid salts
or compounds into their acid and basic constituents or elements by electrolysis
and has for its object to provide improved means and methods for effecting this
result in such a manner that the said elements will not be contaminated by the salts
being dissociated, and so that the ions or their products may be withdrawn from
time to time without stopping the operation; to provide means whereby the liquid
salts may be supplied or submitted to the electrolytic action as desired, and, where
solutions of salts in some menstruum are employed, the depleted or weak solution be
withdrawn and re-saturated; and further to decrease resistance, thus economizing
the electrical energy exerted to dissociate the salts and convey the ions to their
respective electrodes.
My invention consists in employing a body or bodies of liquid electrolyte or
solution of salt to be dissociated, and independent bodies of other liquid; in
separating the bodies of electrolyte from the independent bodies of liquid through
the agency of a liquid conductive medium of greater density than either of said
bodies and by means of walls or partitions between the electrolyte and the
independent bodies which extend below the surface of. said heavy liquid or con-
veyer of ions; in exposing the liquid electrolyte and the independent bodies of
liquid to the action of an electric current through suspended electrodes; and
supplying and withdrawing the liquid electrolyte and independent liquid bodies
with the absorbed or combined ions, without stopping the operation.
The apparatus which I have employed to carry out this process is illustrated in
the accompanying drawings, in which like letters of reference designate corre-
sponding parts throughout, and in which :
Figure 1 is a plan view of a device embodying my invention.
Figure 2 is a longitudinal central section of the same taken upon the line x-x,
Figure 1.
Figure 3 is a transverse section upon the line y-y, Figure 2.
Figure 4 is a similar section upon the line z-z, Figure 2.
Figure 5 is a longitudinal vertical section of a modified form of apparatus, taken
upon the line y' y' Figure 6.
Figure 6 is a horizontal section upon the line ¹¹ Figure 5.
Figure 7 is a longitudinal vertical section taken through the exact centre of a
further modification.
Figure 8 is a plan view of an apparatus for conducting the process in connection
with molten salts.
Figure 9 is a section of the same upon the line 2-2, Figure 8.
The apparatus for dissociation of haloid salts in aqueous solution as shown in
Figures 1, 2, 3 and 4 consists of a main or common tank A, divided by partitions
or porous diaphragms B into compartments A', A³, for the anodes and cathodes
respectively of which I have shown two anode and three cathode compartments;
said partitions B extending wholly across the tank from the top thereof nearly to

page_text: the bottom, sufficient space being left beneath the same for the communicating
liquid which separates the electrolyte from the independent bodies of liquid.
Over the anode compartments A', I secure transverse domes C, resting upon
oblong and sectionally angular frames or peripheral shoulders a secured to the
partitions and to the sides of the tank near the top, and provided with a continuous
upwardly projecting flange a¹ thereon, said domes having an opening b¹ in the top
thereof from which branches off a pipe b, to carry off gaseous products eliminated
during the dissociation of haloid salt, the said pipes & leading to a common pipe b²,
and the bottom of the domes are sealed by the liquid electrolyte above the
shoulders a.
Suspended in said compartments A¹ upon conducting wires D' inserted through
the domes, are the anodes D, preferably three in number, of a length to extend
appreciably above the partitions B, in order not to contact with the separating
and ion-conveying liquid, the level of which is indicated by dotted line 1-1,
Figure 2.
In the compartments Are supported the cathodes E, of which I have shown
three, and which depend-fromaas many plates. secured to transverse beams c¹ up.n
the top of the tanks, and having conductors E¹ secured to said plates.
Immediately above the level of the separating liquid are inserted in the sides of
the tank, inlet pipes d, leading into the anode compartments A', and outlet pipes e'
leading to the cathode compartments A². And near the top of the tank, upon
a substantial level with the surface of the liquid electrolyte, as indicated
by dotted line 2-2, Figure 2, are inserted inlet pipes d', leading from
the cathode compartments A³, and outlet pipes e, leading from the anode
compartments.
The anode inlet pipes d, and the cathode inlet pipes are each connected
together by main pipes ƒ, f¹, and the anode outlet pipes e, and cathode outlet
pipes by main pipes g, g'; and all of said main pipes are provided with stop-
cocks or valves, by means of which the contents of the tank may be added
to or withdrawn,
In the practice of my invention for the dissociation of common salt (sodium
chloride) in aqueous solution, into sodium hydroxide (hydrate) and chlorine gas,
I proceed as follows:
The dense body of separating liquid or conveyer of ions having first been
introduced into the tank to the level indicated, strong brine is produced and slowly
passed by way of the inlets d into the anode compartments A', chlorine gas
being eliminated during electrolysis and collected in the domes C, whence it
is conducted therefrom through the anode outlets e and pipe g to a proper
reservoir.
.
At the same time water containing a small percentage of caustic soda in order to
make it conductive is passed by way of the cathode inlets d' into the cathode
compartments A², care being taken to constantly maintain the electrolyte, or brine,
and the water at a uniform level in their respective compartments, in order not
to disturb the equilibrium of the denser body of conductive liquid employed to
separate the electrolyte from the independent bodies of liquid in the cathode
compartments and serve as a medium for transfer of ions from one compartment to
the other; otherwise the said separating and conveying liquid would become
diffused through the liquids of the several compartments, thereby weakening the
same and reducing its specific gravity to a degree when it would cease to separate
the said liquids.
The body of liquid which I prefer to employ to separate the liquid electrolyte
from the independent bodies of liquid, for the electrolysis of common salt, is caustic
soda in saturated solution, the salt solution supplied to the anode compartment
being more or less dilute in order that its specific gravity may always be less than
that of the separating solution of caustic soda. Care must also be taken to ensure
that the anode extends no further than the lowest level of the salt solution as were
it to project into the caustic soda solution, the soda would be dissociated into

page_text: This is
oxygen or hydrogen as final products, thus evaporating the water solution without
dissociating sodium chloride, which would amount to loss of power.
prevented by drawing off the solution from the cathode compartment before it
becomes dense enough to raise said communicating liquid in the anode
compartment to the height of said anode; and suitable mechanical means, as
valves and hydrometers, may be employed for the automatic regulation of such
withdrawal.
During the process of electrolysis of aqueous solution of sodium chloride, chlorine
gas is eliminated at the anode as before described and the electro positive element
or cation (sodium) passes through the dense separating liquid to the cathode, where
it is liberated and being in the presence of water immediately decomposes the same,
producing sodium hydroxide (hydrate) liberating hydrogen gas as a secondary
product; from which compartment it is withdrawn from time to time as required,
through the outlet pipes e and e¹.
In dissociating common salt in aqueous solution by ectrolysis, I have discovered
that the operation is facilitated by the addition to the brine of a small quantity of
sulphuric acid or solution of some sulphate which will generate acid under electro-
lysis, the free acid assisting in the dissociation of chloride. Phosphoric acid or
phosphates or other oxy-acid or salt of oxy-acid, which is not volatile under the
conditions existent during electrolysis, may be employed. Where molten salts are
used, oxy-acid or the salt of the same, is dissolved in the molten bath. The
presence of the oxy-acid at the anode also tends largely to prevent the oxidation
and disintegration of said anode, the affinity of the oxy-acid anhydride for water
being greater than chlorine for the hydrogen of the water, thus preventing the
formation of hydrochloric acid and free oxygen.
It is obvious that in passing a solution of electrolyte and other body of liquid
through their several compartments to absorb or combine with ions liberated
during the electrolytic action, the current or flow of the liquids must be
regulated at such height above the saturated communicating liquid (in this
case caustic soda solution) that it will not be disturbed but permitted to remain
in a state of tranquillity, and thereby not become diffused through the
liquids.
It will be observed that I introduce the electrolyte into the anode compartments
at the bottom and draw the same off at the top, and exactly the converse with the
liquid in the cathode compartments, the specific gravity of the first being compara-
tively great and that of the latter but slight. I may, however, as shown in
Figures 5 and 6, carry off or if desired introduce, the liquids from or into their
compartments by means of vertical pipes i, projecting through the bottom of the
tank to immediately above the level of the communicating liquid, to one side of the
electrodes, said pipes being in number preferably three for each compartment, and
secured to main pipes i'.
In Figure 7, I have illustrated a further modification of apparatus, in which but
two electrodes are shown, and one of the partitions B is secured to the bottom of
the tank to form an intermediate chamber A³ between the anode and cathode
compartments A' and A³, which chamber communicates with the cathode compart-
ment A3 by means of the dense separating liquid, which rests at the height of the
dotted line 1-1, above which is the outlet pipe i, and in this chamber A is intro-
duced a liquid solution of sulphate of soda up the line 3-3, beneath which are
the inlet pipes; and in the anode compartment A¹ is the electrolyte, with the
addition of a percentage of sulphuric acid, overflowing the bottom partition B, and
resting at the usual height, as indicated by dotted line 2-2. In this form, among
other advantages, I absolutely prevent contact of the anode with the dense separating
liquid, by reason of their mutual remoteness.
I do not confine myself to any one separating body, as any other dense
liquids which are conductors of electricity may be employed, without departing
from the spirit of my invention or process, with the restriction, however, that
such liquids must be maintained in quiescence to prevent diffusion; nor is the

page_text: invention limited to the dissociation of solutions of salts, as it is equally applicable
to salts or compounds in a molten condition, the principle of operation remaining
the same.
In Figures 8 and 9, I have illustrated a modified apparatus especially adapted
for the dissociation of molten salts or compounds, which comprises an iron or other
metallic cauldron or melting pot G, suitably supported in the top of a furnace H,
divided similarly to the tank A by means of an iron or other partition B' into the
two compartments, the anode compartment being preferably lined with carbon or
other carbonaceous material to prevent deteriorating action of the liberated gases
upon the cauldron; and the electrodes being provided with insulating coatings or
casings of asbestos and suitably suspended in the compartments. The commu-
nicating liquid in this device is molten lead, maintained in such condition through
the heat of the furnace; common salt being melted in the anode compartment and
caustic soda in the cathode compartment.
In practice, I support at each side of the cauldron two supplemental cauldrons I, I³,
connecting to the anode compartment A' by means of pipes k, and similar caul-
drous J, J¹ connecting to the cathode compartment A by pipes 1, each of said
supplemental cauldrons being closed by a cover K, and the cathode compartment
of the main cauldron by a cover K¹.
The molten caustic soda is conducted into the cathode compartment A² from the
cauldron J, in which it is melted, and from said compartment to the cauldron J',
where it is treated with live steam, in order to change any sodium oxide (produced
by decomposition of caustic soda in the presence of nascent sodium at the cathode)
into sodium hydroxide; otherwise the caustic soda would eventually become so
saturated with the sodium oxide that a much higher tension of current would
be needed to continue the operation, by reason of the increased resistance
from the presence of such sodium oxide and thus increase the cost of
operation.
To effect this treatment of the caustic soda and regulate the same, I connect to
the cauldrons J and J a forked pipe L, having a three-way stop-cock m at the
commencement of its fork L', and pipes M leading into the respective arms of said
fork L and provided with stop-cocks m'; the three-way cock m serving to connect
the main pipe 1. to either arm of the fork L' exclusively.
A similar series of pipes is arranged in connection with the anode cauldrons I, 1',
to the end that the molten sodium chloride may be thereby caused to circulate
about the anode from the cauldron I to the cauldron 1'.
By dissolving sodium sulphate or other salt of an oxy-acid in the molten
electrolyte the operation is facilitated, inasmuch as such acid salt assists in the
dissociation of the electrolyte and the liberation of gaseous or volatile electro-
negative constituents.
By heating the aqueous solution in the anode compartment especially, the
liberation and elimination of chlorine is considerably facilitated, such heating
preventing to a large degree the diffusion of the chlorine, and thereby enabling its
readier withdrawal. I may also, in the other forms of apparatus, introduce the
electrolyte into the anode compartments in a heated condition, thus effecting a like
result; and I claim this heating to be both novel and highly advantageous, and
therefore a direct improvement in this class of devices and processes.
The use of the various modifications herein set forth and illustrated is optional
or dependent upon the class of work and the invention is in no manner restricted
to either of the same.
I am aware that there are processes which consist in separating electrolyte and
bodies of liquid by means of a moving body of liquid metal, such as mercury.
The communicating body of mercury, however, is not employed for transfer of
ions, but a mere mechanical transfer of products of dissociation; namely, of
amalgam of sodium, produced by electrolysis in one compartment and mechanically
transferred to another compartment where it is subjected to separate electrical
action, the electrolytic process being complete and independent in each cell or

page_text: compartment, the ions not being conveyed by electrical means from one compart-
ment to another. The separating medium (mercury) is also connected in each
compartment with the electrical conductor, so that it becomes anode in one, and
cathode in the other. Were quicksilver employed in my process, the body of
mercury would act merely as a conductor of ions, would not be electrically con-
nected with the electric circuit to form either anode or cathode in the different
compartiments, nor would it be moved to any appreciable degree, but would remain
in a comparatively tranquil state; hence the difference between the two processes
may be easily seen.
In using the word "tranquil" throughout this Specification, I have reference
to a substantially quiescent state of the liquid with respect to other liquids or
bodies, as distinguished from a body of liquid flowing or caused to continually
move by mechanical means.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what 1
claim is:
1. The process for electrolysis of liquid salts or compounds, which consists in
employing a bath of electrolyte and an independent body of liquid, separating said
liquids from each other by means of a body of liquid having greater specific
gravity, said body being in a state of tranquillity and acting as a.conveyer of ions,
in suspending, supporting, or immersing, electrodes in the electrolyte and indepen-
dent body of liquid, and passing a current of electricity through the electrolyte
and bodies of liquid, substantially as described.
2. The process for electrolysis of liquid salts or compounds, which consists in
employing a plurality of baths of electrolyte and independent bodies of liquid,
separating said liquids from each other by means of a body of liquid having
greater specific gravity than either said body being in a state of tranquillity, and
acting as a conveyer of ions, in suspending, supporting, or immersing, electrodes in
bodies of electrolyte and independent bodies of liquid and passing a current of
electricity through the electrolyte and bodies of liquid, substantially as described.
3. The process for electrolysis of liquid salts or compounds, which consists in
employing a bath of electrolyte and an independent body of liquid, separating said
liquids from each other by means of a body of liquid having greater specific
gravity, said body being in a state of tranquillity, and acting as a conveyer of ions,
in suspending, supporting, or immersing electrodes in the electrolyte and indepen-
dent body of liquid, supplying fresh electrolyte from time to time, maintaining the
electrolyte in a state of circulation during action, and passing a current of
electricity through the electrolyte and bodies of liquid, substantially as described.
4. The process for electrolysis of liquid salts or compounds, which consists in
employing a bath of electrolyte and an independent body of liquid, separating
said liquids from each other by means of a body of liquid having greater specific
gravity, said body being in a state of tranquillity, and acting as a conveyer of
ions, in suspending, supporting, or immersing, electrodes in the electrolyte and an
independent body of liquid, supplying fresh liquid to the independent bodies of
liquid and withdrawing said liquid with absorbed or combined ions from time to
time as required, maintaining said body of liquid in a state of circulation, and
passing a current of electricity through the electrolyte and bodies of liquid,
substantially as described.
5. The process for electrolysis of liquid salts or compounds, which consists in
employing a bath of electrolyte and independent bodies of liquid, separating said
liquids from each other by means of a body of liquid having greater specific
gravity, said body being in a state of tranquillity, and acting as a conveyer of ions
from anode to cathode compartments, in suspending, supporting, or immersing,
electrodes in the electrolyte and independent bodies of liquid, supplying fresh
electrolyte, and fresh liquid to the independent bodies of liquid in their respective
receptacles from time to time as required, maintaining the same in a state of

page_text: circulation about the electrodes during action and withdrawing the depleted liquid
electrolyte and the independent bodies of liquid with dissolved or combined ions
as required, and passing a current of electricity through said electrolyte and bodies
of liquid, substantially as described.
6. In a process of electrolytic dissociation, the performing or effecting of
electrolysis of liquid salts or compounds by means of electrodes suspended,
supported or immersed, in a body of electrolyte and independent body of liquid, by
maintaining the electrolyte and bodies of liquid in a state of circulation in and
through their respective compartments about electrodes and separating said
circulating electrolyte and bodies of liquid from each other by means of a more
dense liquid in a tranquil state, said tranquil liquid acting as a conveyer of ions
from and to the several anode and cathode compartments, and by passing a current
of electricity through the bath of electrolyte and bodies of liquid, substantially as
and for the purpose set forth.
7. In a process of electrolytic dissociation, the performing of electrolysis of
liquid salts or compounds, by means of electrodes, suspended, supported, or
immersed, in moving or circulating bodies of liquid consisting of the salt or
compound to be dissociated, and bodies of liquid to absorb or combine with ions
liberated during electrolysis, these moving free circulating bodies of liquid being
separated by a liquid medium of greater density, acting as a conveyer of ions from
and to the anode and cathode compartments and being in a tranquil or quiet state,
and by passing a current of electricity through the moving of circulating liquids and
tranquil separating liquid to the several compartments and electrodes, substantially
as and for the purpose set forth.
8. In a process for the dissociation of liquid binary salts by electrolysis which
embodies the use of a liquid electrolyte, the addition to or introduction into said
electrolyte of an oxy-acid or salt of an oxy-acid before or during the operation,
substantially as described.
9. In a process for the dissociation of binary salt solution, of the general class
or species described, the employment of a heated circulating electrolyte, for the
purposes specified.
10. The process of dissociating binary salt solutions into their acid or basic
constituents which consists in employing a heated electrolyte, and one or more
independent bodies of liquid, to absorb or combine with the ions liberated, in
separating the same from each other by means of a liquid or liquefied conductive
medium of greater density, in bringing electrodes into contact with the heated
electrolyte, and independent body or bodies, and passing an electric current through
said electrodes, substantially as described.
11. The process of dissociating liquid salts or compounds, or the like, which
comprises in its operation the introduction of a liquid electrolyte and an
independent liquid body into a suitable apparatus, and the separation and commu-
nication of said liquids by a liquid conductive medium of such form, condition,
density, or gravity as to remain in a tranquil state, distinct from either of said
liquids, and connect the same together, to act as a conveyer of ions, substantially
.as described.
12. An apparatus for conducting the dissociation of liquid salts or compounds,
or the like, which comprises a receptacle divided by partitions into compartments
having communication beneath said partitions, said receptacle being adapted to
receive therein a liquid conductive medium, inlet and outlet pipes leading to and
from the compartments above the operative level of said conductive medium for
the continuous introduction and withdrawal of the liquids to and from said com-
partments, and electrodes supported in said compartments, substantially as shown
and described.
13. An apparatus for conducting the dissociation of liquid salts or compounds,
or the like, which comprises a receptacle divided by partitions into compartments
having communication beneath said partitions, said receptacle being adapted to
receive therein a liquid conductive medium, anodes and cathodes supported in said

page_text: compartments, domes over the said anode compartments, inlets to the anode com-
partments near the bottom and outlets near the top, and inlets to the cathode
compartments near the top and outlets at the bottom, all of said inlets being above
the practical level of the conductive medium, substantially as shown and described.
14. An apparatus for conducting the dissociation of liquid salts or compounds,
or the like, which comprises a receptacle suitably divided into compartments and
adapted to receive a liquid conductive medium therein, inlets and outlets to said
compartments, one or more of which are downwardly projecting pipes open above
the practical level of the conductive liquid, and electrodes in said compartments,
substantially as shown and described.
15. An apparatus for conducting the dissociation of liquid or liquefied salts or
compounds, or the like, which comprises a receptacle divided into compartments in
which are supported electrodes, and means for heating said receptacle and the salts
or compounds therein, substantially as shown and described.
16. An apparatus for conducting the dissociation of liquid or liquefied salts or
compounds, or the like, which comprises a cauldron supported in a suitable furnace,
and divided by a partition into two communicating compartments, in which are
supported electrodes, and supplemental cauldrons in communication with each of
said compartments, and having inlet and outlet pipes therein, substantially as
shown and described.
Dated this 18th day of December 1894.
WHEATLEY & MACKENZIE,
40, Chancery Lane, London, W.C., Agents.