Improvements in Apparatus for Electrolysis.
Year: 1899

page_text: Improvements in Apparatus for Electrolysis.
I, PAUL SCHOOP, Electrochemist, of Wildegg, Canton Argau, Switzerland, do
hereby declare the nature of this invention to be as follows:-
This invention relates to apparatus for electrolysis without a diaphragm in
which the main disadvantage dependent on the absence of a diaphragm, namely
the tendency for the useful product formed at the one electrode to become recon-
verted into the original compound, or changed into another useless compound,
at the second electrode, is much reduced.
For this purpose the effective surface of one of the electrodes (or electrode sides)
is made several times smaller than that of the other its action upon the product
formed at the other electrode being the more gradual the smaller it is, so that a
better yield of useful product is obtained than is the case when the electrodes
are of the same size. In addition, the electrodes are double-poled, that is, they
are anodes on the one side and cathodes on the other.
A convenient ratio between the electrode surfaces is from 15 to 1: 10, and
it depends on the kind of change to be effected by the electrolysis whether the
anode or the cathode is the smaller. For example, when the required chemical
change is a reduction, as, for instance, the preparation of amidophenol from nitro-
phenol, the surface of the cathode or cathode sigle is extended as much as possible
and the anode surface is proportionally reduced.
If, on the other hand, the action is an oxidation as, for instance, in manufactur-
ing bleaching liquor the cathode surface must be reduced and the anode extended.
In both cases the electrode surfaces must be symmetrically placed relatively to
each other to insure uniformity of current density and a maximum of useful
effect, and they must be as close to each other as possible.
.
Furthermore, the electrolyte must come in contact with the electrodes quite
uniformly. Heretofore a stirrer has been used to keep the electrolyte in motion,
a complicated and costly method. The present improved apparatus has the advan
tage that by reason of the small cross-section of its cells, and the arrangement of
the electrodes above each other or side by side, the intermixture of the products
formed at the electrodes is always in progress at every point.
The electrolyte can be supplied to the electrolyser either intermittently or con-
tinuously, the latter method being preferable, as then the electrolysed solution
can be withdrawn continuously. In many apparatus with continuous supply and
discharge the construction and dimensions are such that the liquid does not come
into uniform contact with the electrode surfaces, leading to the formation of
threads of electrolyte which are not properly electrolysed while in other cases an
rregular speed of flow takes place which is always a disadvantage. On the other
hand with my improved construction all these defects are obviated.
It is generally better to place the electrode at which the larger evolution of
gas occurs above the other electrode so that the gas bubbles in escaping upwards

page_text: through the horizontally moving liquid may cause an eddying motion therein.
Moreover, the gas, escaping at the surface of the liquid, passes away at once and
causes little or no foaming.
The accompanying drawings shew as an example of the improvements referred
to above, forms of apparatus suitable for the electrolysis of a solution of common
salt of 5 per cent. strength.
Figs. 1 and 2 are diagrammatic views of an apparatus consisting of metal
troughs of rectangular V-shaped cross section arranged horizontally one above the
other and acting as electrodes Fig. 3 is a section along the line A-B of Fig. 2.
The salt solution flows into the upper most trough and thence through the over-
flow pipe to the next trough, and so on, as indicated by the arrows in Fig. 2.
The overflow pipe of each trough is at such a level that the surface of the liquid
just covers the angle of the trough next above.
The troughs are in electrical communication with each other only through the
salt solution between them, so that when the lowest trough is connected with the
positive pole of a source of electricity, while the highest is connected with the
negative pole, electrolysis begins. In this manner the inner surface of each trough
becomes an anode the external surface being a cathode. The effective surface of
this cathode, however, is only the angle of the trough in contact with the liquid
below it and the rapid evolution of hydrogen thereat serves in a measure to still
further reduce the contact by keeping off the solution to some extent. The inner
sides of the trough on the other hand act as anode over their whole surface, and
the caustic soda sinking from the angle of the trough above mixes so completely
with the chlorine dissolved in the rapidly moving liquid that secondary phenomena
(chiefly the electrolytic decomposition of caustic soda) are suppressed as far as
possible. The product (sodium hypochlorite) which conducts electricity some-
what feebly, is always followed by fresh salt and in this manner a common salt
solution of only 5 per cent. strength can be electrolysed so that the resulting
bleaching liquor contains up to 1 per cent. of active chlorine.
The EMF between two troughs is only 45. volts. The efficiency, calculated on
the current supplied, is from 10 to 90 per cent, according to the content of the
resulting liquid in active chlorium:
Thus a sufficiently strong bleaching solution can be obtained from a dilute salt
solution with a fair efficiency, and from a salt solution containing 10 per cent. of
common salt a bleaching liquor containing from 15 to 2 per cent. of active chlorine
can be prepared such results have not heretofore been realised.
If the electric current is reversed, chlorine is evolved in considerable quantity,.
passing into the air, and the bleaching liquid falls correspondingly in strength.
Fig. 4 represents a more advantageous form of trough. A similar but corres-
pondingly more massive cross section is maintained when the frough is con-
structed of graphite; Fig. 5 shews the construction of such a trough, in which
the small electrical resistance of this arrangement is to be noted, as the cross
section of the conductor is very large but the length unusually small.
Instead of arranging the troughs above one another they may be placed side by
side. Fig. 7 is a plan of such an apparatus, which has a separate feed and outlet
for each trough. Fig. 6 is a section along the line ab of Fig. 7.
In the constructions shewn in Figs. 2 and 3, there is communication between
the salt solution in the separate troughs, so that a loss of electricity is apt to
occur owing to a part of the current passing through the whole length of the
liquid instead of through the electrodes: such portion of the current is mainly
expended in heating the liquid. This loss may be avoided by supplying each
trough with liquid from a separate reservoir and leading the overflow tube of
each trough into a separate vessel. An apparatus of this kind is shown in plan
in Fig. 8 and in cross section in Fig. 9. The columns of liquid are in this case
independent of each other, and the arrangement is such that one flat sheet of
electrode is exposed in unequal surfaces on its two faces to the liquid Long,

page_text: Harrow, strips of electrode are clamped longitudinally between plates of insulat-
ing material, like glass or ebonite.
With poorly conducting electrolytes the loss of current due to short circuiting
by the liquid is not of much importance, in which case the apparatus shown in
cross section in Fig. 10 and in plan in Fig. 11 may be used advantageously. The
electrolyte is introduced into the uppermost trough and passes down the series,
being compelled to take the longest course as shown by the arrows in Fig. 11.
In all the above constructions it may happen that in the course of time the
sheets of electrode become perforated or cracked and the electrolyte passes directly
through them from one trough to the next, whereby the regular circulation is
interfered with and short circuiting by the liquid becomes considerable, and re-
newal of the electrode is necessary. Fig. 12 shows in section and Fig. 13 in plan,
an apparatus in which the last named objection is obviated. The troughs are
arranged on an inclined plane, for example they may be set in a glass plate,
or the troughs may be made in the manner shewn in Figs. 9 and 11. Instead of
having overflow pipes each trough is here prolonged in a curve at the end down-
wards to the next following trough, the whole system thus forming a single trough
winding backwards and forwards across an inclined plane. In each of these glass
troughs is a double electrode having the cross section shewn in Fig 14; when
the troughs are full of liquid the solution effects a connection between the double
electrodes as shewn in Fig. 12. The direction of the current of liquid is indicated
by arrows in Fig. 13 and flows in this case in the direction contrary to that of
the electric current. A further reduction of the cathode surface is here achieved
by notching it on one side whereby at the same time the formation of gas pockets
s avoided. Finally, the glass plate is pierced with horizontal tubular passages
arallel to its faces; these may be connected at their ends in any suitable manner
nd then serve, as a system for cooling the apparatus by passing cooling water
hrough them, which is an advantage in hot weather.
When the apparatus is built up of strips as already described, each strip may
ave a semicircular groove along its faces; so that two grooves fitted together
ake a tube.
Dated this 23rd day of Juna 1900.
ABEL & IMRAY,
Agents for the Applicant.
I, PAUL SCHOOP, Electrochemist, of Wildegg, Canton Aargau, Switzerland, 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 apparatus for electrolysis without a diaphragm in
which the main disadvantage dependent on the absence of a diaphragm, namely
the tendency for the useful product formed at the one electrode to become recon-
verted into the original compound or changed into another useless compound at
the second electrode, is much reduced. Furthermore the efficiency of the electric
current applied to my apparatus is increased, since the resistance of the electrodes
as well as of the solution to be electrolyzed, is reduced to the smallest amount.
This is done by bringing the electrodes together as near as possible, and is made
practically possible by the peculiar arrangement of the electrolytic troughs. As
will be hereinafter described, my electrodes are so-called double-poled electrodes

page_text: and have the form of long, but rather narrow troughs, lying parallel and very near
to each other. The one side or end of each electrode always reaches over into the
trough, formed by the next electrode or in a trough, wherein the next electrode
is placed. The troughs are in electrical communication with each other only
through the salt-solution (or solution to be electrolyzed) between them. By
properly regulating the surface of the electrolytic solution in these troughs, it
may be arranged that just the end of the upper-lying or nearest electrode dips
in the fluid.
In this way the electrodes are not only symmetrically arranged, but the one
side, for instance the cathode, is always placed vertically over the opposite elec-
trode or anode. Whilst the solution to be electrolyzed flows along the trough,
the developement of gases, caused by passing an electric current through the
apparatus, creates an eddying motion of the fluid, thereby mixing automatically
and continuously the fluid, and the products, separated at the two electrodes or
their poles.
As an example, the electrolytic decomposition of a solution of common salt
according to my invention is performed as follows. The effective surfaces of the
two electrodes, or in other words, of the cathode and the anode, are not equal,
but the anode surface is made 5 to 10 times larger than that of the cathode. The
latter just dips into the surface of the fluid, thereby affording a rather small
surface to the solution. The rapid evolution of hydrogen further reduces the
contact with the liquid by keeping off the latter to some extent. The inner side
of the trough, on the other hand, acts as anode over its whole surface and the
caustic soda, working from the cathode above mixes so completely with the
chlorine, liberated at the anode and dissolved in the rapidly moving salt-solution.
that secondary phenomena (chiefly the electrolytic decomposition of caustic soda)
are practically suppressed. The product, sodium-hypochlorite, which conducts
electricity somewhat feebly, is always followed by fresh salt, and in this manner
a common salt-solution of only 5 per cent. strength can be electrolyzed, so that
the resulting bleaching liquor contains up to one per cent. of active chlorine. The
electromotive force between two troughs may vary between 4-5 volts and the
efficiency, calculated on the quantity of current supplied, from 70-90% accord-
ing to the content of the resulting liquid of active chlorine.
Thus a sufficiently strong bleaching fluid can be obtained with a fair efficiency
from a rather diluted salt-solution, whilst from solutions containing 10 per cent.
of salt, bleaching fluids with up to 2 per cent. of active chlorine may be prepared.
Such results have not heretofore been realised.
If the electric current is reversed, chlorine is evolved and passes in consider-
able quantity into the air; the bleaching liquor decreases correspondingly in
strength. On the other hand, there are cases where it is profitable to give the
anode-side a small surface and to let the cathode-surface have an expanded sur-
face. This would be the case whenever it is desired to bring the reducing power
of the cathode into full play. As an example may be mentioned the making of
amidophenol from nitrophenol.
Whether the electrodes he made of graphite or of thin platinum sheets (in
which latter case they are inserted in troughs of insulating material like glass,
ebonite, paraffin and the like), the small electrical resistance of this arrangement
is to be noted, as the cross section of the conductor is very large, but the length
unusually small. The troughs may be arranged above one another, or be placed
side by side. Also groups of troughs can be placed side by side and these groups
arranged above one another, similar to the steps of a stair-case. In the accom-
panying drawings Figs. 1, 2, 3, 4, 5, 6 and 7. shew troughs placed above each
other and in the drawings Figs. 8, 9, 10, 11, 12, 13 and 14 the troughs are placed
side by side.
Figs. 1 and 2 are diagrammatic views of an apparatus consisting of metal
troughs of rectangular V shaped cross section, arranged vertically one above the
other and acting as electrodes. Fig. 3 is a section on line A-B of Fig. 2. The

page_text: salt solution flows into the uppermost trough and thence through the overflow-
pipe to the next trough and so on, as indicated by the arrows in Fig. 2. The
over-flow pipe of each trough is at such a level that the surface of the liquid just
covers the angle of the trough next above. The troughs are in electrical com-
5 munication with each other only through the salt solution between. them, so that
when the lowest trough is connected with the positive pole of a source of electricity
while the highest is connected with the negative pole, electrolysis begins. In
this manner the inner surface of each trough becomes anode, the external surface
being cathode. The effective surface of this cathode, however, is only the angle
of the trough in contact with the liquid below it.
Fig. represents a more advantageous form of trough. A similar but corres-
pondingly more massive cross section is maintained when the trough is constructed
of graphite; Fig. 5 shews such a trough.
In all the above constructions it may happen, that in the course of time the
sheets of electrode become perforated or cracked, allowing the electrolyte to pass
directly through them from one trough to the next, whereby the regular circula-
tion is interfered with and short circuiting by the liquid becomes considerable
so that renewal of the electrode is necessary. Fig. 7 shews in section and Fig. 6
in plan an apparatus, in which the last named objection is obviated. The troughs
are arranged on an inclined plane, for example they may be set in a glass plate
or a block of other insulating and resisting material.
Instead of having over-flow pipes, each trough is here prolonged in a bend at
the end downwards joining on to the next following trough, the whole system thus
forming a single trough winding backwards and forwards across an inclined plane.
In each of these insulating troughs is a double electrode, having the cross section
as shewn in Fig. 7. When the troughs are full of liquid, the solution effects a
connection between the double electrodes as shewn in Fig. 7. The direction of
the current of liquid is indicated by arrows in Fig. 6, and flows in this case in
the direction contrary to that of the electric current. A further reduction of the
cathode surface is here achieved by notching it on one side, whereby at the same
time the formation of gas pockets is avoided. The supporting plate (of glass or
other suitable material) may be pierced with horizontal tubular passages (as shewn
in Fig. 7) parallel to its faces. These may be connected at their ends in any suit-
able manner and may then serve as a system for cooling the apparatus by passing
cooling water through them, which is an advantage in hot weather especially.
In the constructions shewn in the Figs. 1 to 7 there is a communication between
the salt solution in the separate troughs, so that a loss of electricity is apt to
occur owing to a part of the electric current passing through the whole length
of the liquid intead of through the electrodes, such portion of the current being
only expended in heating the liquid. This loss is avoided by the arrangement
according to the Figures 8 to 14.
liquid from a separate reservoir or pipe and the overflow of each trough is led
Each trough is in this case provided with
off separately.
In the arrangement shewn in cross section in Fig. 8 and in plan view in Fig. 9,
the columns of liquid are independent of each other, and each trough has a
separate feed and outlet. The troughs are placed side by side, but the arrange-
ment is such, that also in this case the one end (at the right hand side, Fig. 8)
of each electrode is exposed to the liquid only with a fraction of the surface with
which the opposite side of the next electrode is exposed thereto.
Although with poorly conducting electrolytes, as for instance dilute solutions
of common salt, the loss of current, due to short circuiting by the liquid is not
f much importance, I prefer the arrangement shewn at Figs. 10 to 14, to that
t Figs. 6 and 7: it differs from the latter in that the electrodes are not arranged
n an inclined plane. Groups of six troughs are placed side by side on a hori-
ontal plane, similar to the arrangement shewn by Figs. 8 and 9, and a number
f such groups are combined together stepwise. Fig. 12 shews a plan view.
igs. 10 and 11 shew cross sections of alternative forms, Fig. 13 a longitudinal

page_text: section and Fig. 14 a perspective view of double poled electrode (of the same
kind as applied in Figs. and 7). In a slab A of insulating material such as
glass, ebonite, solid hydrocarbons &c., are formed the channels B running parallel
to each other, which are closed at both ends. These channels are suitably made
of a rectangular cross section as at Fig. 10, or they may be semi-circular as at
Fig. 7and Fig. 11. In the present case they are assumed to be about 1 centi-
metre wide, 1 centimetre deep and 30 centimetres long; the dimensions may,
however, vary, if only the section of the channels be taken small and the distance
of the channels from each other, which in the present case is about ½ centimetre,
be also small.
These long narrow channels lying closely side by side are introduced the double
electrodes of platinum-iridium sheet metal of only 10 millimetre in thickness.
Fig. 14 shews a perspective view of a semi-circular form of electrode. This elec
trode is formed like the letter S and has notches along the one edge. (If the
channels are made rectangular, as shewn in Fig. 10, the corresponding electrode
is formed like the letter %). Each electrode is situated with its unnotched part
in a channel while its other part first rises up out of the channel and then bends
over into the next channel, so that the serrations thereof reach down to the level
of the liquid in such channel. Each channel has a separate supply pipe D for the
solution to be electrolyzed and also a discharge pipe E for the electrolyzed solution.
The direction of the flow of the liquid is indicated by arrows in Figs. 12 and 13.
When all these channels have been provided with double electrodes as described
(there being any desired number of channels, such as six, as shewn in Fig. 12)
and these channels having been filled with the solution to be electrolyzed, the
apparatus is connected to a current generator of sufficient voltage. The electric
current then enters, for example the first electrode C, passes from the notched
parts into the liquid of first channel and through it to the electrode O' from which
the current again issues through the notched part into the solution in the second
channel, and so on, until the current has passed through all the electrodes and
channels, returning from the last of these to the positive pole of the generator.
By a suitable regulation of the supply of liquid and of the quantity of current,
the electrolysis can be carried out within the desired limits.
If several such apparatus are to be employed in combination, they are arranged
in step form, one beneath the other. Fig. 13 shews part of a second apparatus
arranged in this manner, the solution passing from the channels of the first through
pipes E into those of the second. In this way the solution can be enriched to a
certain degree, instead of requiring to pass it repeatedly through one and the
same apparatus for this purpose.
In order to avoid a loss of current at the entrance of the electrolytic solution
in the apparatus, it is necessary to lead the salt solution to each channel by means
of a long and not too thick a pipe or tube, the resistance of the thread of liquid
therein being sufficiently large. In the same manner the exit of each channel of
the lowest apparatus ends in a glass tube of sufficient length, or the threads of
fluids have to drop through air a sufficient distance (say 1 metre) before uniting
in the lower channels.
The electrodes, placed in the channels, are in the present case made of one piece
of sheet metal, but they may also consist of any desired number of pieces, put
together to form a similar electrode. Or, instead of having the double electrodes
pass through the air to reach the fluid-surface of the next trough or channel, they
may penetrate the walls of insulating material and reach into the next channel:
with this more direct arrangement the effective (or active) surfaces of the anode
and cathode part can be regulated at will.
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 apparatus for electrolyzing solutions, especially of alkali chlorides,

page_text: wherein the solution to be electrolyzed is made to flow along long narrow double
poled electrodes, arranged parallel to each other and near together, the effective
surface of the one electrode or side of electrode being made considerably larger
than the effective or active surface of the opposite electrode or side of electrode,
substantially as described.
2. Apparatus for electrolyzing solutions, more particularly of alkali chlorides,
wherein the solution to be electrolyzed is made to flow through long narrow
channels arranged parallel to each other and near together, in which channels are
placed double poled electrodes which dip simultaneously into the liquids of two
contiguous channels, substantially as described.
3. In apparatus for electrolyzing solutions, such as are referred to in Claims 1
and 2, arranging two or more such apparatus stepwise and causing the electro-
lyzed solution to pass from the uppermost apparatus into the corresponding
channels of the next lower one, substantially as described.
4. In combination with apparatus for electrolysis of solutions, double poled
electrodes, in which both sides of the electrode surface take part in the electro-
lyticaction, substantially as described.
5. In apparatus for electrolyzing solutions, wherein the troughs through which
the solution flows, are each provided with a separate supply and discharge for
the solution, which channels are suitably arranged in one and the same plane
and have double poled electrodes that dip simultaneously into the liquid of two
contiguous troughs, substantially as described.
Dated this 22nd day of March 1900.
ABEL & IMRAY,
Agents for the Applicant,