IMPROVEMENTS IN VOLTAIC BATTERIES
Year: 1884

page_text: Wo DESMOND GERALD FITZGERALD of 6 Akerman Road, Brixton, in the
County of Surrey, Electrician, and THOMAS JOHN JONES of 12 Princes Street,
Hanover Square in the County of Middlesex, Electrician, do hereby declare the
nature of the said invention for "IMPROVEMENTS IN VOLTAIC BATTERIES," and
in what manner the same is to be performed, to be particularly described and
ascertained in and by the following statement:-
Our Invention consists in improvements in the construction of negative
elements of voltaic batteries, more especially those in which peroxide of lead is
employed as the "depolarising agent." We have found this substance to be most
efficacious for the purpose in view provided means be taken to obviate the pro-
duction of a "local couple" caused by contact between the peroxide, an oxidizable
support, and the electrolyte. When however such triple contact exists, the
peroxide of lead may be almost or quite inefficacious as a depolarising agent.
When for instance a simple plate of lead in contact with peroxide of lead and
dilute sulphuric acid is employed as the negative element of a voltaic couple, the
electro-motive force of the couple rapidly fails whilst its internal resistance
increases so that the couple becomes almost inoperative whatever may be the metal
employed as the positive element of the couple. The cause of this failure is to be
found in the local voltaic action which occurs between the oxidizable lead and the
oxidising peroxide in presence of sulphuric acid, whereby the surface of the lead
becomes coated with a layer of sulphate of lead which effectually prevents contact
between the metal and the oxidant.
This local action may be prevented by the use of gold or platinum, or greatly
reduced by the use of carbon as the support for the active material as is well
understood.
According to our Invention however we employ as the support for the depolar-
ising agent a conductor such as a plate of lead or silver which is itself susceptible
of oxidation but which wo coat with a first or superficial but dense coating of
peroxide of lead which is preferably rendered impervious by means of a suitable non-
conducting substance such as paraffin-wax (which should be free from stearic acid)
while permitting contact of the depolarising agent with such first coating. Such a
conductor becomes equivalent for the purpose in view to a plate of gold or platinum
insomuch as this first impervious or nearly impervious layer of peroxide constitutes

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an inoxidizable conductor which protects the oxidizable conductor from contact
with the electrolyte and thus obviates local action.
In carrying out our Invention we first obtain a superficial layer of peroxide of
lead upon the surface of any suitable rigid conductor of oxidizable metal or of
carbon, preferably by making such conductor the anode within an electrolyte 5
composed for instance of a solution of oxide of lead in caustic alkali, the peroxide
being allowed to deposit very slowly. The first superficial layer thus obtained may
advantageously be burnished or subjected to pressure between smooth plates or
rollers; it may then be supplemented by a second thin coating of peroxide of lead.
Other electrolytes such as a solution of lead nitrate, dilute sulphuric acid, or a
solution of sulphate of magnesia, may be employed. When however the acid or
the sulphate solution (or any electrolyte which does not contain lead) is used, the
conductor must be lead; the plate must in this case be maintained in the electro-
lyte until oxygen is evolved from its surface when it should be removed, washed
with water, dried, and pressed or burnished. It should then be returned to the
electrolyte until oxygen is again evolved from its surface when it is washed and
dried a second time.
The conductor thus coated with inoxidable conducting material may now be
more completely protected from contact with the electrolyte, when in use, by
immersing it in melted paraffin-wax (or similar waterproofing substance) until the
layer of peroxide of lead is saturated with this material. The latter when cold is
carefully removed by means of a scraper or other suitable tool from the surface of
the plate so as to expose the conducting peroxide of lead of which the pores will
remain filled with the paraffin.
The prepared plate when used may be immersed in a pasty mass of peroxide of
lead with water, a solution of sulphate of magnesia or other suitable fluid, such
pasty mass, alone, or in admixture with carbon fragments, being contained within
a porous receptacle; or this receptacle may be dispensed with and the prepared
conductor may be utilized as a support for a comparatively thick and porous layer
of peroxide of lead obtained by any of the known means, alone or in admixture
with carbon fragments. In this case the element may bo wrapped in canvas, felt,
or other suitable porous material.
Instead of surrounding the inoxidizable support with peroxide of lead itself, said
support may be coated with a pasty mass containing lead to be subsequently
converted by electrolysis into peroxide of lead. For instance we may coat the
inoxidizable conductor or support with a pasty mass of oxide of lead in admixture
with finely divided lead (in the proportion of from one part of the latter to three
or four parts of the former) and then convert this mixture into peroxide of lead by
rendering the coated support the anode in a suitable electrolyte, preferably a
solution of sulphate of magnesia.
The negative elements of our Invention may be employed in conjunction with
any suitable positive element and electrolyte, such as a plate of amalgamated zinc
or of porous lead in dilute sulphuric acid. They may also be used as elements in
secondary batteries.
Although we have described the electrolytic method as the one we prefer for
producing on the surface of the conductive support the protective layer of per-
oxide of lead, we do not limit ourselves thereto as the support may be coated
mechanically with any sufficiently pure peroxide of lead, such as that obtained in
bulk by electrolysis, or by treating red lead with nitric acid.
Having now particularly described and ascertained the nature of the said
Invention and in what manner the same is to be performed, we declare that what
we claim is:-
1* In the construction of a negative element for voltaic batteries, the inter-
position between the conductive support and the depolarising agent of a waterproof
layer of peroxide of lead which is in contact on the one hand with the said support,
and on the other with the depolarising agent, substantially as specified.
•

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2nd The construction of a negative element for voltaic batteries of a support of
any suitable conducting material which has been electrolytically coated with a
dense and adherent first layer of peroxide of lead, in combination with a second
layer or a mass of any suitable description of peroxide of lead in contact with such
electrolytically coated support, substantially as specified.
3 The construction of a negative clement for voltaic batteries of a plate or
support of lead upon which a coating or first layer of dense and adherent peroxide
of lead has been electrolytically produced, in combination with a second layer or a
mass of any suitable description of peroxide of lead in contact with such first layer,
substantially as specified.
4th The method of constructing the negative element of a voltaic battery which
consists in electrolytically producing upon the surface of a plate of lead or other
suitable conductor, a first coating or layer of peroxide of lead, then rendering this
coating or layer impervious to the electrolyte by the application of paraffin-wax
(or other equivalent waterproofing material) in such a way as to fill the pores or
interstices of the coating or layer and leave its surface exposed, and finally
applying the depolarising agent in contact with the said conting or layer,
substantially as specified.
Doted this 10th day of December 1991.