IMPROVEMENTS IN GALVANIC BATTERIES
Year: 1883

page_text: PROVISIONAL SPECIFICATION left by Herbert John Allison at the Office
of the Commissioners of Patents on the 13th August 1883. Communicated
to him from abroad by Alfred Haid, of New Jersey, United States of
America.
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•
HERBERT JOHN ALLISON, of the firm of Allison Brothers, Patent Agents, of
Southampton Buildings, London, IMPROVEMENTS IN GALVANIC BATTERIES"
a communication to me from abroad by Alfred Haid, of New Jersey, United
States of America.
This invention relates to galvanic batteries, and its objects are mainly to obtain
a battery which combines with a capacity for producing a high Electro-motive
force, great constancy, and small size, and to make the battery more portable.
These objects aro attained: First, by the use in conjunction with a positive
Electrodo and a proper solution, of a compound negative Electrode of novel
character, the nature and method of preparation of which will be hereinafter
described, and second, a cell and cover of novel construction.
The negative Electrode is contained in a porous cup or jar of any ordinary
character and consists of a carbon conductor, surrounded by and embedded in a
mixture of carbon and a depolarizing substance insoluble in the liquid of the
battery, in a solid and compact mass.
This Electrode is prepared in the following manner.
A depolarizing substance that is not only itself insoluble, or practically so, in
the liquid of the battery, but of which the products of decomposition are also
insoluble is intimately mixed with powdered carbon. This mixture is then
moistened with dilute acid or other solvent, which being absorbed by the depolarizing
substance, causes the particles of the mixture to cohere and form a compact mass.
While moist, the mixture is formed or applied around a carbon conductor,
preferably by being placed in an ordinary porous cup containing the carbon, when
it rapidly dries and hardens, forming a compact and solid mass.
The depolarizing agent which is used by preference, is mercuric oxide or the
ordinary red precipitate of commerce, though other substances of a similar nature,
such as sesquioxide of iron may be used.
The proportions of carbon and oxide may be obviously varied. For example,
seventy-five per cent by weight of carbon, to twenty-five per cent of red oxide may

page_text: be used to advantage, but as the energy and durability of the battery has been
found to increase with a larger proportion of oxide, it will be found advisable to
mix equal parts by weight of the two substances.
The carbon may be powdered or granulated and in any of the forms commonly
used in batteries of this kind.
For solidifying or compacting the depolarizing substance, dilute nitric or chromic
acid is used, preference being given to the former for the reason mainly that
together with the water it does not form an acid salt, but an insoluble basic salt
and free acid, the result of which is that the zinc electrode is not attacked by the
products of decomposition finding their way through the porous cup.
When dilute nitric acid is added to a mixture of mercuric oxide and carbon, the
acid combining with the oxide forms a basic salt of mercury, but by the great
excess of oxide present, the acid is rapidly absorbed leaving the particles of the
mixture firmly cemented together, the whole mass being compact and dense, but at
the same time porous, an extremely desirable condition and one presenting great
advantages over those forms of battery in which the depolarizing substance is in
loose grains, or where it is solidified by pressure, so that the action is mainly
confined to the surface of the mass.
From the effects produced on the oxide of mercury by the nitric acid, it is evident
that other solvents may be used, such for instanco as nitrate of mercury or any
solution of metallic compounds that cause the particles to cohere and form a
compact mass without cavities or breaks.
In lieu of adding the acid to the mixture of oxide and carbon before it is formed
about the carbon conductor, the spaces about the carbon in the porous-cup-may be
filled in with the dry powder and the powder then solidified by immersing the cup
in dilute acid until it is saturated.
Another method of preparing the negative Electrode is by dissolving mercury in
nitric acid, evaporating the solution until it is concentrated, and then adding the
powdered carbon. The mixture. 'is then formed around a carbon conductor, dried
and heated slowly, which causes the formation of the basic salt which cements the
mass together.
The porous cup after being filled with the carbon and the depolarizing mixture
is closed with pitch, wax, or a similar substance, through which projects a post
embedded in the carbon and provided with means for connection with a wire. A
flexible cover is provided with perforations through which extend the post and the
zinc cylinder. A screw ring is applied to the orifice of the jar over the cover, thus
sealing the cell and preventing evaporation or spilling.
For exciting the battery a solution of sal-ammoniac is used, which is poured
into the outer jar. The action of the battery is remarkably steady and uniform,
and as the depolarizing substance used is not only itself insoluble in the solution,
but gives on decomposition products also insoluble; great durability is secured, for
the reason that the zinc is not affected by the permeation of any soluble products
through the porous cup. The full dissolving capacity of the liquid being thus
preserved, the battery may be made quite small as but little liquid is required.
Other advantages secured by the use of the substances named, are, that by the
decomposition of the oxide, when the battery is active, metallic mercury is formed,
which reduces the internal resistance.