Improvements in Peroxide of Manganese and Carbon Electrodes, and in the Method of Producing the same.
Year: 1896

page_text: Date of Application, 21st Dec., 1896-Accepted, 6th Feb., 1897
COMPLETE SPECIFICATION.
Improvements in Peroxide of Manganese and Carbon Electrodes, and
in the Method of Producing the same.
I, ALBRECHT HEIL of Fränkisch Crumbach, Grand Duchy of Hesse, German
Empire, Electrician, 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 consists of improvements in peroxide of manganese and carbon
electrodes and in the method of producing the same, and it has for its main object to
enable such electrodes to be employed in the construction and working of secondary
batteries.
It is well known that a utilizable electric current can be produced by the electro-
chemical reaction and decomposition in galvanic battery elements only when one
electrode (the positive electrode) is oxidized or chlorinated, whilst the other electrode
(the negative electrode) is able to oxidize, chlorinate and absorb hydrogen at the
same time.
The negative electrode is therefore of very considerable importance in galvanic
batteries because it has the function of destroying or neutralizing the hydrogen that is
set free by the decomposition.
In batteries of the Leclanché type, peroxide of manganese (MnO,) is employed to
act as the oxidizing agent for the hydrogen. The positive electrode consists of zinc
and the electrolyte consists of a solution of sal-ammoniac.
The electro-chemical action in these batteries is as follows:-
The readily chlorinated zinc combines with the chlorine of the sal-ammoniac
solution to form chloride of zinc, and hydrogen is set free which is oxidized by the
oxygen of the peroxide of manganese to form water at the peroxide of manganese
and carbon electrode. The solution of sal-ammoniac however still contains nitrogen
which combines with a certain amount of hydrogen to form ammonia therewith at
the oxidizing places of the peroxide of manganese. This ammonia escapes, and thus
abstracts nitrogen from the sal-ammoniac, so that the solution becomes gradually
changed, in consequence. As a result of the formation of ammonia there is further
produced hydrated oxide of zinc at the surface of the peroxide of manganese and
carbon electrode.
These drawbacks are particularly felt when it is desired to construct secondary
batteries with the ordinary oxide of manganese and carbon electrodes, because after
the electrolyte has been decomposed by the discharge of current the original substances
cannot be re-formed again. Ammonia has escaped, and hydrated oxide of zinc has
been formed. It is impossible by subsequent charging of these elements to re-form
and regenerate or convert those materials into the original substances.
Now the method which constitutes this present invention has for its object to
produce peroxide of manganese and carbon electrodes which shall not be affected
by the aforesaid drawbacks and which can therefore be employed in secondary
batteries.
The electrodes which are composed of carbon (graphite) and peroxide of manganese
(MnO,) and which are preferably made of zig-zag or corrugated form in cross
section, are placed in a solution which contains chlorine but does not contain nitrogen
(such for example as a solution of chloride of magnesium or a solution of chloride
of sodium) and are reduced by the action of
current from a separate or extrnal

page_text: source to a certain extent, the hydrogen acting to abstract oxygen from, the peroxide
of manganese. The electric current is then passed in the reverse direction through
the solution and the oxide of manganese and carbon electrode. This acts to further
decompose the solution and to form at the reduced peroxide of manganese and carbon
electrode, chlorine which combines with this electrode to a certain extent, and thereby
converts the said electrode into a compound of chlorine.
On removing the electrode thus treated from the solution and on placing the said
electrode together with a zinc electrode again into a solution of sal-ammoniac, then
on current being taken or discharged from the cell no ammonia, and therefore also
no hydrated oxide of zinc will be produced in the cell, because the chlorine that was
abstracted from the sal-ammoniac by the chlorine compound of the zinc is replaced
by the chlorine of the reduced and chlorinated peroxide of manganese and carbon
electrode, as the hydrogen now combines with the chlorine of this electrode.
The solution of sal-ammoniac is thereby maintained in its initial proper condition
or composition, as are also the electrodes, and it is therefore possible to produce
practically useful secondary batteries with these electrodes.
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 I
claim is :-
1. The method of producing peroxide of manganese and carbon electrodes, which
consists in reducing these electrodes before use, in an electrolyte (that contains
chlorine but is free from nitrogen) by the action of an electric current from a separate
or external source, and in then converting the said electrodes into chlorine compounds
by reversing the current, substantially as hereinbefore described.
2. Peroxide of manganese and carbon electrodes produced according to the method
specified in the preceding claim, substantially as herein before described.
Dated this 21st day of December 1896
J. C. MEWBURN & ELLIS,
55 and 56 Chancery Lane, London, Chartered Patent Agents.