Improvements in the Methods of Effecting the Electrolysis of Saline Solutions.
Year: 1894

page_text: Date of Application (in United Kingdom), 22nd Mar., 1894
Complete Specification Left, 22nd Mar., 1894-Accepted, 16th June, 1894
COMPLETE SPECIFICATION.
Improvements in the Methods of Effecting the Electrolysis of Saline
Solutions.
We LOUIS ALPHONSE PAUL LIÉNARD and HENRI EUGÈNE ALBERT
LIENARD, both of 15 Rue des Halles, Paris, in the Republic of France, 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 has for its object methods and processes for use in the electrolysis
of saline solutions, and particularly of the soluble chlorides of sodium, potassium,
calcium, and magnesium, and the soluble carbonates of soda and potash.
In order to explain clearly in what our methods and processes consist, we
describe them below with respect to Figs. 1, 2, 3 and 4 of the annexed drawings
which we will suppose applied for example to the production of chlorine gas and
caustic soda by the electrolysis of chloride of sodium dissolved in water.
Fig. 1 is a vertical section through the anode, which may be rectangular or
circular.
Fig. 2 shows the manner in which is formed the bottom of the partition in metal
woven cloth gauze.
Fig. 3 shows the inclination given to the folded bottom of the partition, for the
disengagement of the hydrogen gas, and
Fig. 4 shows a vertical section of the complete apparatus.
REFERENCES.
A positive electrode, or anode, formed of sticks or pencils a a of animal carbon,
inserted at convenient distances in the wood surface band consolidated on each side
of this surface-after having been first electrically connected-by a mass of paraffin
melted and poured thereon, this electrode resting by its outer surface, also of wood,
in an iron case B the bottom of which is formed of bent metal cloth. C, outer
container acting as negative electrode. DD, insulating supports on which the
case Brests. c, collector tubes liberating the hydrogen coming from the lower bath
through the small tubes d d and which can be, by means of another collecting tube,
removed from the solution. ee, inclined surfaces of the metal cloth. ff, inclined
9 tube
plane angles each covered by a small cap of thin sheet iron, pierced at d.
by which escapes the chlorine disengaged from the saline liquid under treatment.
The electrolysis of sea salt in solution with water is a well known fact, but
the high price of electric energy was one of the principal obstacles to the
application of this process for the industrial production of chlorine gas and caustic
soda. The recent introduction of the electric dynamo has enabled this energy to be
obtained at a price allowing the industrial formation of these products by
electrolysis.

page_text: Further obstacles however opposed the practical realisation of the operation
In effect, and for the first thing, it is known that the products of the decomposition
have a tendency to recombine in the bath, as they are formed, and this tendency
is assisted also by the agitation in the bath produced by the abundant disengagement
of hydrogen at the negative electrode.
These products are; on the one hand around the anode, the acid elements, and
on the other, around the cathode, the basic elements which, as may be seen from
their nature, have a great tendency to recombination and salification. By reason
of this difficulty the interposition has been effected, between the two electrodes, of
a partition which allows both of the separation of the products and the passage
of the electric current, conditions which a porous partition would fulfil, which
formed the greatest possible obstacle to salification and the greatest possible electric
conductivity.
These two conditions are antagonistic. In effect the electric conductivity of a
porous partition is in direct ratio to the sum of the sections of the capillary spaces
which exist in a unit of surface whilst the opposition to salification through a porous
partition is in inverse ratio to this same sum of the sections of the capillary spaces.
If therefore a good partition is used from the point of view of opposition to
salification a greater electro motive force will have to be employed resulting in an
increased cost in the production. If a good partition is used from the electrical
point of view, a partial recombination of the decomposed elements will result and
consequently a low output which will also give a high cost of production.
Other conditions have also to be realised. It is necessary that the substance of
this partition be composed of a material easily worked, offering a sufficient resistance
to strain and compression, in order that it may be manufactured with a large surface
of little thickness and with the least mass. Furthermore these partitions must be
staple, that is to say, must resist the corrosive action of the elements in the bath
and preserve their good qualities from the two theoretical points of view indicated
above, that is to say, their capillary ducts must not choke up nor augment in
section.
Experience has shown us that the best porous partitions of earthenware or of
animal or vegetable parchment, and of similar kind were inferior from all the points
of view above indicated, to a partition the molecules of which were not united to
each other in an invariable manner; and that the most suitable substance to realise
the desired industrial object was ground carbon which presents furthermore the
advantage of very good electric conductivity, and of being unaffected by the
elements of the bath. Such a material however being in small fragments
non adhesive between themselves, cannot constitute by itself a vertical partition; it
is necessary therefore to employ an envelope to hold it.
Now all the envelopes tried on the anode side have been attacked by the chlorine;
but on the contrary, a metallic sheet on the cathode side has a good resistance.
We have thus been led to place the electrodes horizontally, the anode being
placed uppermost. This arrangement allows of one metal sheet only being used,
serving to support the material constituting the partition.
This method of procedure however offers two inconveniences :-
1st. Carbon plates cannot be used as anodes or else they must be provided with
holes for the disengagement of the chlorine gas, and this presents certain
inconveniences.
2nd. The disengagement of the hydrogen which forms on the kathode is restricted
by the porous partition placed immediately above.
It was necessary to remedy these difficulties and we have effected this in the
following manner.
This
We have insured the liberation of the hydrogen by giving to the metal cloth,
which supports the ground carbon, the suitable shape as shown by Fig. 2.
metal cloth instead of being arranged horizontally is first folded over on itself in
the shape of an accordeon in such manner as only to present surfaces inclined to

page_text: the horizontal as shown in the figure. The gases when disengaged meet these
inclined surfaces and slide along these inclines resting in the plane angle above
which form a channel. Each of these channels is surmounted by another channel
of thin iron plate attached to the metallic cloth in such manner as to prevent the
gas passing through the cloth through the plane angle. If these channels are
then slightly inclined two by two in the direction of their length, to the horizontal
as shown in Fig. 3, and at the upper part or summit of the angle formed by the
two adjacent channels there is an outlet tube opening into a collector tube c to
which also a certain inclination may be given in both directions or in one only, the
difficulty above pointed out will be removed.
The manufacturing apparatus constructed under the conditions which have just
been indicated would present the arrangements shown by Fig. 4.
The positive electrode is placed above the layer of ground carbon occupying
the lower part of the case B having iron sides and the bottom made of metal cloth
arranged as we have just indicated. This case rests on the insulating supports DD
placed on the bottom of another receptacle C also of iron which serves as negative
electrode.
The space between the vertical sides of the receptacle B and the vertical sides
of the anode A may be filled with refined or ordinary sea salt, or by any other
corresponding salt in solution, or even, as with the bottom by ground carbon in
such manner as to intercept the communication between the interior of the anode
and the liquid in the receptacle C. The operation of the apparatus may thus be
made continuous and it is not necessary to take it apart since in proportion as the
solution became weaker in salt it would dissolve a portion of the salt interposed
between the surfaces, or introduced in any other manner easily devised.
By proceeding in this manner and without the corrosion of any portion of the
apparatus, chlorine gas is obtained, and also caustic soda which remains in solution
in the vessel G. When this solution is sufficiently concentrated it is withdrawn
and replaced by fresh salt water and so on.
We reserve to ourselves the right to construct our apparatus of any shape or
size and of any suitable material, provided that the essential characteristics of our
invention remain it being understood that we may apply the said apparatus to the
electrolysis of all decomposable saline solutions.
Having now particularly described and ascertained the nature of our said inven-
tion and in what manner the same is to be performed, we declare that what we
claim is :-
1. The special combination of the positive electrode or anode A of multiple
pencils a a fixed in a wooden cross piece b and after being electrically connected at
their heads consolidated by two layers of melted paraffin on each side of the
surfaces b, a tube g serving for the escape of the chlorine liberated by the anode.
2. The intermediate metallic case B carried by the insulators D D the bottom of
which made of folded metallic cloth, receives an inert pulverizable material
preferably ground carbon of the required degree of porosity, and on which bottom,
thus prepared, the anode A rests, the space between this anode and the surfaces of
the case B being also filled with ground carbon or with a quantity of fine or
granulated salt corresponding to the solution submitted to electrolysis.
3. In the intermediate case mentioned in the preceding claim, the small inclined
channel made of thin sheet iron arranged along the length of the apex of each of
the plane angles formed by the faces e e of the folded metallic cloth, leading, at
the summit of the angle formed by the apex of the two adjacent plane angles into the
tube d opening into the collector tubes c c of the hydrogen disengaged at the
kathode, which hydrogen may be removed from the saline solution.
4. The receptacle C serving as the horizontal negative electrode, in combination
with the positive electrode A and the special partition interposed between the two
electrodes and insulated by the supports D. D.

page_text: 5. The process and apparatus substantially as described in the foregoing
.Specification and illustrated in the accompanying drawings.
Dated this 22nd day of March 1894.
WHEATLEY & MACKENZIE,
40, Chancery Lane, London, W.C., Agents.