By MM. F. DE LALANDE and G. CHAPERON.
We have succeeded in forming a new battery with a single liquid and
with a solid depolarizing element by associating oxide of copper,
caustic potash, and zinc.
This battery possesses remarkable properties. Depolarizing electrodes
are easily formed of oxide of copper. It is enough to keep it in
contact with a plate or a cell of iron or copper constituting the
positive pole of the element.
Fig. 1 represents a very simple arrangement. At the bottom of a glass
jar, V, we place a box of sheet iron, A, containing oxide of copper,
B. To this box is attached a copper wire insulated from the zinc by a
piece of India rubber tube. The zinc is formed of a thick wire of this
metal coiled in the form of a flat spiral, D, and suspended from a
cover, E, which carries a terminal, F, connected with the zinc; an
India-rubber tube, G, covers the zinc at the place where it dips into
the liquid, to prevent its being eaten away at this level.
The jar is filled with a solution containing 30 or 40 per cent. of
potash. This arrangement is similar to that of a Callaud element, with
this difference--that the depolarizing element is solid and insoluble.
[Illustration: FIG. 1.]
To prevent the inconveniences of the manipulation of the potash, we
inclose a quantity of this substance in the solid state necessary for
an element in the box which receives the oxide of copper, and furnish
it with a cover supported by a ring of caoutchouc. It suffices then
for working the battery to open the box of potash, to place it at the
bottom of the jar, and to add water to dissolve the potash; we then
pour in the copper oxide inclosed in a bag.
We also form the oxide of copper very conveniently into blocks. Among
the various means which might be employed, we prefer the following:
We mix with the oxide of copper oxychloride of magnesium in the form
of paste so as to convert the whole into a thick mass, which we
introduce into metal boxes.
The mass sets in a short time, or very rapidly by the action of heat,
and gives porous blocks of a solidity increasing with the quantity of
cement employed (5 to 10 per cent.).
[Illustration: FIG. 2.]
Fig. 2 represents an arrangement with blocks. The jar V, is provided
with a cover of copper, E, screwing into the glass. This cover carries
two vertical plates of sheet-iron, A, A', against which are fixed the
prismatic blocks, B, B, by means of India rubber bands. The terminal,
C, carried by the cover constitutes the positive pole. The zinc is
formed of a single pencil, D, passing into a tube fixed to the center
of the cover. The India rubber, G, is folded back upon this tube so as
to make an air-tight joint.
The cover carries, besides, another tube, H, covered by a split
India-rubber tube, which forms a safety valve.
The closing is made hermetical by means of an India rubber tube, K,
which presses against the glass and the cover. The potash to charge
the element is in pieces, and is contained either in the glass jar
itself or in a separate box of sheet-iron.
Applying the same arrangement, we form hermetically sealed elements
with a single plate of a very small size.
The employment of cells of iron, cast-iron, or copper, which are not
attacked by the exciting liquid, allows us to easily construct
elements exposing a large surface (Fig. 3).
[Illustration: FIG. 3.]
The cell, A, forming the positive pole of the battery is of iron plate
brazed upon vertical supports; it is 40 centimeters long by 20
centimeters wide, and about 10 centimeters high.
We cover the bottom with a layer of oxide of copper, and place in the
four corners porcelain insulators, L, which support a horizontal plate
of zinc, D, D', raised at one end and kept at a distance from the
oxide of copper and from the metal walls of the cell; three-quarters
of this is filled with a solution of potash. The terminals, C and M,
fixed respectively to the iron cell and to the zinc, serve to attach
the leading wires. To avoid the too rapid absorption of the carbonic
acid of the air by the large exposed surface, we cover it with a thin
layer of heavy petroleum (a substance uninflammable and without
smell), or better still, we furnish the battery with a cover. These
elements are easily packed so as to occupy little space.
We shall not discuss further the arrangements which may be varied
infinitely, but point out the principal properties of the oxide of
copper, zinc, and potash battery. As a battery with a solid
depolarizing element, the new battery presents the advantage of only
consuming its element, in proportion to its working; amalgamated zinc
and copper are, in fact, not attacked by the alkaline solution, it is,
therefore, durable.
Its electromotive force is very nearly one volt. Its internal
resistance is very low. We may estimate it at 1/3 or 1/4 of an ohm for
polar surfaces one decimeter square, separated by a distance of five
centimeters.
The rendering of these couples is considerable; the small cells shown
in Figs. 1 and 2 give about two amperes in short circuit; the large
one gives 16 to 20 amperes. Two of these elements can replace a large
Bunsen cell. They are remarkably constant. We may say that with a
depolarizing surface double that of the zinc the battery will work
without notable polarization, and almost until completely exhausted,
even under the most unfavorable conditions. The transformation of the
products, the change of the alkali into an alkaline salt of zinc, does
not perceptibly vary the internal resistance. This great constancy is
chiefly due to the progressive reduction of the depolarizing electrode
to the state of very conductive metal, which augments its conductivity
and its depolarizing power.
The peroxide of manganese, which forms the base of an excellent
battery for giving a small rendering, possesses at first better
conductivity than oxide of copper, but this property is lost by
reduction and transformation into lower oxides. It follows that the
copper battery will give a very large quantity of electricity working
through low resistances, while under these conditions manganese
batteries are rapidly polarized.
The energy contained in an oxide of copper and potash battery is very
great, and far superior to that stored by an accumulator of the same
weight, but the rendering is much less rapid. Potash may be employed
in concentrated solution at 30, 40, 60 per cent.; solid potash can
dissolve the oxide of zinc furnished by a weight of zinc more than
one-third of its own weight. The quantity of oxide of copper to be
employed exceeds by nearly one-quarter the weight of zinc which enters
into action. These data allow of the reduction of the necessary
substances to a very small relative weight.
The oxide of copper batteries have given interesting results in their
application to telephones. For theatrical purposes the same battery
may be employed during the whole performance, instead of four or five
batteries. Their durability is considerable; three elements will work
continuously, night and day, Edison's carbon microphones for more than
four months without sensible loss of power.
Our elements will work for a hundred hours through low resistances,
and can be worked at any moment, after several months, for example. It
is only necessary to protect them by a cover from the action of the
carbonic acid of the atmosphere.
We prefer potash to soda for ordinary batteries, notwithstanding its
price and its higher equivalent, because it does not produce, like
soda, creeping salts. Various modes of regeneration render this
battery very economical. The deposited copper absorbs oxygen pretty
readily by simple exposure to damp air, and can be used again. An
oxidizing flame produces the same result very rapidly.
Lastly, by treating the exhausted battery as an accumulator, that is
to say, by passing a current through it in the opposite direction, we
restore the various products to their original condition; the copper
absorbs oxygen, and the alkali is restored, while the zinc is
deposited; but the spongy state of the deposited zinc necessitates its
being submitted to a process, or to its being received upon a mercury
support. Again, the oxide of copper which we employ, being a waste
product of brazing and plate works, unless it be reduced, loses
nothing of its value by its reduction in the battery; the
depolarization may therefore be considered as costing scarcely
anything. The oxide of copper battery is a durable and valuable
battery, which by its special properties seems likely to replace
advantageously in a great number of applications the batteries at
present in use.
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