Improvements in Electrolytical Condensers and Electric Current- directing Devices.
Year: 1898

page_text: PROVISIONAL SPECIFICATION.
Improvements in Electrolytical Condensers and Electric Current-
directing Devices.
I, CHARLES POLLAK, of 253, Mainzer Landstrasse, Frankfort-on-the-Main, in
the German Empire, Managing Director of the " Accumulatoren-Werke System
Pollak," do hereby declare the nature of this invention to be as follows;-
These improvements relate to the subject matters of Letters Patent No. 1069
dated Jan. 15th 1896 and the Application for Letters Patent No. 23442
dated Oct. 12th 1897, both of which subject matters are based on observa-
tions of the behaviour of certain metals such as aluminium when subjected
to the action of electrical current in electrolytical cells. When an aluminium
electrode for example contained in an electrolytical cell is connected to the
positive pole of a source of current and when current is sent through such
electrode it will in a short time become enveloped in an insulating polarization
coat, or layer. When however the current passes through in the opposite
direction no such insulating coating forms but the coating previously formed
is reduced in part, so that now the aluminium electrode offers no appreciable
resistance to the current tending to pass through it. As the insulating coat
formed by electrolysis has a very thorough insulating action as is extremely
thin a cell of this description may be utilized as a statical condenser of great
capacity wherein the plates and fluid form the two linings whilst the polariza-
tion coating constitutes the dielectricon of the condenser. This capacity which
as compared to that of the condensers hitherto known is very considerable may
be readily determined by measurement, while such capacity may be further
added to in a simple manner by extending the area of the porous plates or by
arranging them as electrodes.
In order to enable such fluid condensers to be made use of in circuits worked
by alternating currents an electrolytical cell with two aluminium electrodes of
like polarity should be switched into the circuit. When this is done one or
the other of the electrodes will alternately act as a condenser as the current
passes through while at the same time the other plate owing to the reduction
of the insulating layer under the action the correspondingly directed current
will serve as a leading-off or escape electrode. The sudden changes in the
polarization coating of the two plates, which are necessary in this case and which
must follow the alternations of the reversible current, take place in a perfectly
satisfactory manner.
A third form of these cells, wherein one electrode is aluminium while the
other consists of some metal such as lead which offers no material resistance to
the current flowing in either direction, may be employed for an almost infinite
variety of purposes as these cells only allow current impulses to traverse them
in one direction viz.from the lead to the aluminium and never inversely
the consequence being that they may serve as means of protection from back-
currents or as apparatus for making current-impulses pass through in a pre-
CD

page_text: determined direction so that they may be used in imparting a uniform direction
to alternating currents and may consequently be described as determinators
of the direction of currents.
The employment of aluminium or kindred electrodes as condensers or means
for determining the direction of currents has hitherto been attended by the
drawback that the insulating coating of the plates could not without difficulty
be formed in a sufficiently complete manner since the slightest impurity in
the metal would cause disturbances difficult to remove. The arrangement here
described however supplies a means for making use of what is known in the
trade as pure' aluminium for the purpose stated and enables such slight
impurities as that metal contains to be disregarded as it obviates any of those
disturbing effects which they would otherwise produce. The formation of
the insulating layer on the plates is effected in the following manner:
The plates are steeped in an alkaline or neutral solution with an addition
of bichromate of potassium or of another suitable chrome compound and con-
nected to the, positive pole of the source of current. If desired however solutions
of bichromate of potassium or other chrome compounds with but a slight
addition of alkalies may answer the same purpose. When the current begins
to act there forms in a short time on the aluminium plate a perfect insulating
coat or layer capable of withstanding differences of electro motive force amount-
ing to or exceeding 100 volts. This layer develops readily and quickly and is
not to any material extent dependent upon the degree of concentration of the
solutions; and it furthermore possesses this quality so important in a current-
transformer that as the direction of the current is reversed it undergoes an
almost instantaneous change and accordingly offers no material resistance to
the current. In those cases where the object is not to bring about a quick change
of the resistance but only to ensure a very high degree of resisting force to
pressures of 200 volts or upwards soap solutions may with advantage be sub-
stituted for the aforesaid solutions. Under the action of the current they will
then form on the electrode connected to the positive pole of the source of current-
metal soaps insoluble in water which will surround such electrode with a perfectly
insulating layer or coating and even when opposed by high voltages will behave
as almost perfect insulations. The layers obtained by this method however
have the peculiarity of changing but slowly when the direction of the current is
reversed so that they can only in some cases be employed as determinators of the
direction of currents or as current-condensers.
Dated this 12th day of January 1898.
JOHNSONS & WILLCOX,
47, Lincoln's Inn Fields, London, W.C., Agents.
Improvements in Electrolytical Condensers and Electric Current-
directing Devices.
I, CHARLES POLLAK, of 253, Mainzer Landstrasse, Frankfort-on-the-Main, in
the German Empire, Managing Director of the "Accumulatoren Werke System
Pollak," 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:
These improvements relate to the subject matters of Letters Patent No. 1069
dated January 15th 1896 and. the application for Letters Patent No. 23442

page_text: dated October 12th 1897 both of which subject matters are based on observa-
tions of the behaviour of certain metals, such as aluminium, when subjected
to the action of electrical current in electrolytical cells. When an aluminium
electrode, for example, contained in an electrolytical cell, is connected to the
positive pole of a source of electricity, and when current is sent through such
electrode, it will, in a short time, become enveloped in an insulating polarization
coat or layer. When however the current passes through in the opposite
direction no such insulating coating forms but the coating previously formed
is reduced in part, so that now the aluminium electrode offers no appreciable
resistance to the current tending to pass through it. As the coating formed
by electrolysis is a good insulator and is extremely thin, a cell of this descrip-
tion may be utilized as a statical condenser of great capacity wherein the plates
and fluid form the two linings, whilst the polarization coating constitutes the
di-electricon of the condenser. This capacity which, as compared to that of
the condensers hitherto known, is very considerable may be readily determined
by measurement, while such capacity may be further increased in a simple
manner by extending the area of the plates, or by providing them with a porous
surface.
In order to enable such fluid condensers to be made use of in circuits worked
by alternating currents, an electrolytical cell with two aluminium electrodes
should be switched into the circuit. When this is done one, or the other
of the electrodes will, alternately act as a condenser as the current passes
through, while, at the same time, the other plate, owing to the reduction of the
insulating layer under the action of the correspondingly directed current will
serve as a leading-off, or escape electrode. The sudden changes in the polariza-
tion coating of the two plates, which are necessary in this case, and which must
follow the alternations of the reversible current, take place in a perfectly satis-
factory manner.
A third form of these cells, wherein one electrode is aluminium while the
other consists of some metal, such as lead, which offers no material resistance
to the current flowing in either direction, may be employed for an almost infinite
variety of purposes, as these cells only allow current impulses to traverse them
in one direction viz: from the lead to the aluminium, and never inversely, the
consequence being that they may serve as means of protection from back-
currents, or as apparatus for making current-impulses pass through in a pre-
determined direction, so that they may be used in imparting a uniform direction
to alternating currents and may consequently be described as rectifiers of the
direction of currents.
The employment of aluminium or kindred electrodes, as condensers, or means
for rectifying the direction of currents, has hitherto been attended by the draw-
back that the insulating coating of the plates could not, without difficulty, be
formed in a sufficiently complete manner, since the slightest impurity in the
metal would cause disturbances difficult to remove. The arrangement here
described however supplies a means for making use of what is known in the trade
as pure aluminium for the purpose stated and enables such slight impurities,
as that metal contains, to be disregarded as it obviates any of those disturbing
effects which they would otherwise produce. The formation of the insulating
layer on the plates is effected in the following manner.
The plates are placed in an alkaline, or neutral solution, with the addition
of 3 or more per cent. of bi-chromate of potassium, or of other suitable chrome
compound, and connected to the positive pole of the source of electricity. If
desired, however, solutions of bichromate of potassium or other chrome com-
pounds, with but a slight addition of alkalies (for instance about 1 per cent.)
may be used to answer the same purpose. When the current begins to act there
forms in a short time, on the aluminium plate, a perfect insulating coat, or layer,
capable of withstanding differences of electro-motive force amounting to ог
exceeding, 100 volts. This layer developes readily and quickly, and is not, to

page_text: any material extent, dependent upon the degree of concentration of the solu-
tions; and it furthermore possesses this quality, so important in a current-
transformer, that as the direction of the current is reversed it undergoes an
almost instantaneous change, and accordingly offers no material resistance to
the current. In cases where the object is not to bring about a quick change
of the resistance, but only to ensure a very high degree of resisting force to
pressures of 200 volts, or upwards, soap solutions may with advantage be
substituted for the aforesaid solutions. A 5 per cent. soap solution is usually
taken but its strength is in fact immaterial. Under the action of the current
they will then form on the electrode connected to the positive pole of the source
of electricity metal-soaps insoluble in water, which will surround such electrode
with a perfectly insulating layer or coating, and even when opposed to high
voltages will behave as almost perfect insulators. The layers obtained by this
method however have the peculiarity of changing but slowly, when the direction
of the current is reversed so that they can only in some cases be employed as
rectifiers or as condensers.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed, I declare that what I
claim is:-
-
Condensers or current rectifiers consisting of electrolytical cells, with electrodes
either in solutions of alkalis with the addition of chrome compounds or in soap
solutions, the electrode connected to the positive pole of the source of electricity
receiving an insulating coating by electrolytic action.
Dated this 12th day of October 1898.
JOHNSONS & WILLCOX,
47, Lincoln's Inn Fields, London, W.C., Agents.