Improvements in the Method of and Apparatus for the Electrolytical Separation of the Bases of Salts and of Compounds of the same from Saline Solutions.
Year: 1893

page_text: Date of Application, 1st Feb., 1893
Complete Specification Left, 1st Dec., 1893-Accepted, 27th Jan., 1894
PROVISIONAL, SPECIFICATION.
Improvements in the Method of and Apparatus for the Electrolytical
Separation of the Bases of Salts and of Compounds of the same
from Saline Solutions.
I, CLAUDE THEODORE JAMES VAUTIN of 42 Old Broad Street, in the City
of London, Metallurgical Chemist do hereby declare the nature of my invention
to be as follows :-
My invention relates to the separation by electrolysis of the bases of salts and
of compounds of the same from saline solutions and has for its object.the carrying
out of such a process in a more perfect manner than heretofore, whereby any
secondary action is prevented such as takes place in the reaction between the
liberated base and the solution of the electrolyte (for example the decomposition
of H,O by Na when aqueous salts of Na aro electrolysed); further it permits the
base of the salts to be obtained in a metallic state or as an amalgam, or in the form
of a solution of any desired salt; also the necessity of using a diaphragm of the
usual form is obviated and thus the electrical resistance of such a diaphragm is
eliminated from the bath.
I carry out my invention by taking advantage of the property known as the
surface tension of liquids and I apply that principle in the following manner
taking for example in order to facilitate description, the decomposition of a soluble
salt of sodium.
I have found that the surface tension of metallic mercury is of such a naturo
that under certain conditions it will not run or pass through a sieve so long as the
mesh of the sievo is not too large, for example, a 60 hole to the inch sieve will
support a considerable head of mercury without the mercury falling through.
In applying this fact to electrolysis, I employ a sieve of such construction of
suitable material such as horse hair silk wire etc. or any material not acted on by
either the electrolyte or mercury upon which is supported a layer of mercury
which forms the cathode and undor which is preferably immediately arranged a
suitable anode.
For example the electrolysis of sodium conducted in such an apparatus would be
as follows:-The sodium would be deposited upon the under side of the mercury
and would form an amalgam with it, and in consequence of the less specific gravity
of the amalgam compared with mercury, it would rise up through the mercury to
the surface thereof, and should caustic soda be the combination wished, water
would be placed in the sieve on the surface of the mercury, which would be
decomposed by the sodium of the amalgam forming caustic soda. If however
metallic sodium is desired oil or other inert material would be placed on the surface
of the mercury.
It will be clearly seen that it is impossible for the solution of the caustic soda
produced to be in any way contaminated by being mixed with any still
undecomposed electrolyte as is the case in the majority of electrolytical
arrangements in use.
By the above described arrangement of the mercury, a large percentage of the
surface of the cathode is in actual contact, with the electrolyte, for the clear area
of the meshes of the sieve are filled with mercury, hence all the disadvantages of
diaphragms as at present used viz.: electrical resistance, the diaphragm becoming
destroyed, or choked are obviated.
The production of several metals and many of their salts can be obtained by the
application of the above arrangement of mercury cathode, and when a metal is to

page_text: be obtained that decomposes water; oil or other inert substance can be placed on
mercury and the amalgam produced removed from time to time and the metal
separated from the mercury of the amalgam by any suitable method. It is obvious
that I may arrange the siove as a partition in the tank in a position other than
horizontal in order to separate the mercury from the electrolyte.
Dated this 1st day of February 1893.
J
FELL & WILDING,
1, Queen Victoria Street, London, E.C., Agents for the Applicant.
Improvements in the Method of and, Apparatus for the Electrolytical
Separation of the Bases of Salts and of Compounds of the same
from Saline Solutions.
1, CLAUDE THEODORE JAMES VAUTIN, of 42 Old Broad Street in the City
of London, Metallurgical Chemist, do hereby declare the nature of my invention,
and in what manner the same is to be performed to be particularly described and
ascertained in and by the following statement:-
My invention relates to apparatus for use in cells for tho separation of bases from
their salts, or of constituents from chemically combined compounds, by electrolysis,
and consists in the arrangement and construction of a mercury electrode, whoreby
actual metallic contact between such an electrode and the electrolyte is secured,
with minimam internal resistance to the passage of the current, and with valuable
commercial results in the treatment of certain electrolytes.
Whereas it is known that the employment of a mercury cathode in the electro-
lysis of certain solutions, in which the base will form an amalgam with mercury, or
will pass through the mercury, offers great advantages for the separation of the
base from the electrolyto, preventing it from re-combining therowith, or
decomposing water that may be present, but no means for supporting a fixed
mercury electrode las hitherto been known, except porous pots, or diaphragms of
earthenware, parchment, gelatinous material, or materials impregnated with starch;
all of which offer great resistance and waste energy to the passing of the electrical
current, and in no way afford a true metallic contact between the electrolyte and
the mercury cathode.
My invention therefore consists in means for so supporting the mercury cathodo,
that it is retained in stable position, and yot affords a considerable percentage of
area for actual metallic contact with the electrolyte; and further, affords a distinct
barrier against the passage of the electrolyte through it, whilst auy base which is
capable of amalgamation with the morcury or capable of passing through the
mercury, either in a free state or as an amalgam, will pass through the mercury
cathode without ro-contact with the electrolyte.
And in order that my invention may be the better understood, I now proceed to
describe the same in reference to the drawings hereto annexed, and to the letters
and figures marked thereon.
Figure 1 is a sectional view of an electrolytical cell, with specially supported
horizontal mercury cathode.
Figure 2 is an enlarged detail of the sieve supporting the mercury cathode.
Figure 3 is a further enlarged corner of said sieve, showing amalgam looking
joint.
Figure 4 is a sectional view of an electrolytical cell, with specially supported
vertical mercury cathode.
Figure 5 is a side elevation of the vertical mercury cathode.
Figure 6 is a modification of same.
Figure 7 is an enlarged detail section of one mercury chamber in vertical
electrode, showing internal amalgam locking joint.

page_text: Figure 8 is a sectional view of an electrolytic cell, with specially supported
diagonal mercury cathode.
find, that mercury, by reason of what is termed "its surface tension" will not
pass through the apertures of a reticulatod mesh or siovo or a finoly perforated shoot,
up to a coarseness of about 60 meshes to the inch, or equivalent fineness of
perforations, without considerable shock or pressure; and that the surface tension
of the moronry, or its resistance to such passage, will support a small layer or head
of mercury from falling through the sieve, in obedience to the ordinary law of
gravity.
I find that such a mosh or sieve, which may be constructed of metallic wire,
silk, or any other convenient fibre, will whilst supporting a certain layer or head of
mercury, expose a surface of metallic mercury through the apertures of the siove,
of about 60 per cent. of the whole area of the sieve or mercury layer.
I therefore employ anch a mesh, or sieve, or perforated plate, as an external
support of a mercury cathode, for employment in an electrolytical cell, and 1 find
that such mesh must be made of a material non-conducting to electricity; or if, of
metal, must be protected by a non-conducting coating, so as not to interfere with,
or substitute itself for, the desired action of the mercury electrode in the
electrolyte.
In Figure 1 I show an electrolytic cell, provided with an anodo A, and a mercury
cathode B, in an electrolyte C, the cathode being supported by a mesh or perforated
plate b, (ns herein above described) in a chamber D, from which the electrolyte C
is entirely excluded by the cathode, and the side walls of the chamber D.
Any other suitable liquid, such as water G, may be introduced into the chamber D,
above the cathodo B, to produce any secondary chemical action with tho "cation,"
which if of lighter density than, or forming an amalgam with, the mercury, will
pass through it, and rise into the chamber D.
As the said "surface tension" of the mercury, causes it to assume a spheroidal
shape at its side periphery touching the walls of the chamber D, the actual surface
contact of the mercury, under these circumstances, with the walls of the chamber D,
would be of small area, compared with the depth of morcury resting upon the
supporting sieve, and might allow the electrolyte to leak through. therefore
apply a strip of metal a (Figures 2 and 3) about the edge of the chamber con-
taining the mercury; such strip to be of a metal, which will form with the mercury
an amalgam, so as to scize and attract the mercury to such locking joints, making a
secure liquid-tight joint, and enabling me to use a very shallow layer of mercury
over the body of the mesh or sieve b.
I prefer to use a strip of iron, coated with sodium amalgam, because the iron
metal strip does not become deteriorated by the action of the sodium amalgam upon
it, and the sodium amalgam has a great affinity for the mercury. Or, the vessel
may be made of metal, iron preferred, and insulated except at the lower inner
bottom edge, in line with the sieve surface.
The bottom or surface of the mercury supporting vessel must be made flush,
without engagement pockets, to admit of the free escape of the hydrogen or other
gas that may be freed upon the under face of the mercury electrode.
Where I desire to use a mercury cathode in a vertical_position to divide the
cell absolutely into two liquid-tight compartments (as in Figure 4), one of which
compartments E may be filled with the electrolyte C, on one side of the mercury
cathode F, and the other compartment D may be filled with water G or other
liquid, I construct the mercury electrode in the following manner.
I take a plate of metal, which is a conductor of electricity, preferably iron, and
protect the faces and edges by non-conducting material, such as vulcanized indin-
rubber &o.
I form transverse slots H, Figure 5, or orifices K, Figure 6, of any desired
shape in the said plato to contain mercury, each portion of mercury being thus
distinct from the other, and only subject to a small head of liquid mercury prossure
when placed vertically, I cover the faces of the electrode by the before describel

page_text: non-conducting mesh, articulated tissue, or perforated plate b, making secure
joints between the mesh and the metal faces of the plate around the slots or
orifices.
I find this mesh or tissue sufficient by the "surface tension" of the mercury to
retain the liquid mercury in its individual recesses or compartments; and, to
further assist the retention of the mercury, and to make a close liquid-tight joint
around the walls of the mercury compartments, I apply around the interior of the
compartment (Figure 7) sodium amalgam; or amalgamate the inner surface of the
compartments, so that they attract the mercury and form a secure locking joint,
also helping to retain the mercury in the compartinent.
Where an oblique electrode is desired, I arrange it in the form shown in
Figure 8, where the mercury is supported on the said mesh, sieve, or perforated
plate b, and I divide the mercury into n series of steps or terraces by intermediate
divisions L (each side of the partition to be amalgamated) so that the actual
liquid head of mercury, on the sieve or mesh is reduced to any desired minimum,
by the closeness of the terrace divisions; and this arrangement allows an easy
escape for the gases formed on the under-face of the electrode. A solution of
water or other liquid may be placed over the said mercury electrode.
In the above arrangements of cells any suitable anode A may be used, and any
convenient arrangement for the removal of gaseous anions or cations by pipes M,
and hoods and pipes M', from a closed chamber in the upper part of the cell, or
constant supply of the electrolyte E by pipes N, or removal by pipes P of the
water or other liquid G separated from the electrolyte by the mercury cathodo F,
may be used.
It is obvious that this improved mercury electrode will be of extreme utility in
the electrolysis of saline solutions, such as NaCl, whereby tho sodium is deposited
upon the mercury cathode, and passes through it as a sodium amalgam, which may
be collected as it issues from the mercury; or if water is present at the back of
the cathoile, the sodium of the amalgam is at once converted into caustic soda,
which is entirely separated from the original electrolyte.
I therefore find I can obtain a solution of caustic soda, entirely free from the
electrolyte, and of any strength; thus. avoiding any intermediate process that
might otherwise be required for the separation of the caustic soda from the
electrolyte; and I find that I can effect this separation by my improved apparatus
at a low cost, owing to the low internal resistance of the cell, and the exceptionally
small E. M. F. of current required.
I may however employ my improved mercury enthode, as hereinabove described
in any form of electrolytical cell, for which it is adaptable, without departing
from the essence of my invention.
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 :-
1st. A mercury electrode, for use in electrolytical cells, consisting of liquid
mercury, supported by a reticulated mesh or sieve or perforated plate of non-
electrical-conducting material, or externally insulated, substantially as described.
2nd. In a mercury electrode, a joint, composed of metal, capable of amalga-
mation with mercury, and internally surrounding the chamber, containing the
mercury, tho orifice of said chamber being covered by a supporting electrically-
non-conducting or insulated reticulated mesh, sieve, or perforated plate, substan-
tially as described.
3rd. In a mercury electrode, a metallic conducting plate, insulated as to its
outor surface, and containing mercury, in slots or apertures of any shape, the
external faces of said apertures being closed by a non-conducting or insulated
reticulated mesh, sieve, or perforated plate, supporting the mercury therein,
substantially as described.
4th. In a mercury electrodo, an electrically non-conducting or insulated

page_text: reticulated mesh, sieve, or perforated plate, provided with parallel upright
divisions, to support. mercury thereon, in a series of steps or terraces, when the
support is placed obliquely in the cell, substantially as described.
6th. The general arrangements and construction of parts of an electrolytical
cell provided with a mercury cathode, substantially as described and illustrated
berewith.
FELL & WILDING,
1, Queen Victoria Street, London, E.C., Agents for the Applicant.