Improvements in or connected with Negative Elements (Positive Electrodes in Charging Secondary Cells) of Voltaic Batteries.
Year: 1891

page_text: Date of Application, 6th June, 1891
Complete Specification Left, 7th Mar., 1892-Accepted, 9th Apr., 1892
PROVISIONAL SPECIFICATION.
Improvements in or connected with Negative Elements (Positive
Electrodes in Charging Secondary Cells) of Voltaic Batteries.
I DESMOND GERALD FITZ-GERALD of 46 Loughborough Road, Brixton, in
the County of Surrey, Electrician, do hereby declare the nature of this invention
to be as follows
:-
Hitherto in utilizing the highly conductive slabs mainly composed of peroxide of
lead known under the name of lithanode" it has been necessary to use a strip of.
platinum or gold in order to establish electrical contact with the material. It has
in fact been found (if we exclude the rarer metals belonging to the platinum group)
that platinum only will withstand prolonged use as an anode in the electrolysis of
dilute sulphuric acid. A practical contact with a plate of lithanode can, however,
be effected by means of a strip of gold held (as in the case of the platinum strip)
in close contact with the lithanode by means of a strip of insulating material
attached to the element by means of bolts and nuts. The cost of establishing
contact in the manner described by means of platinum or gold has been found so
great as in many cases to be prohibitive. According to this invention a thin layer
of gold or of platinum or of both is or are applied by electro-deposition or other-
wise upon the whole or a portion of a strip, tang, contact piece, or washer of lead
or lead alloy.
The precious metal so deposited upon the lead or lead alloy allows of the
passage of the electric current from the lead strip or the like to the lithanode
without allowing the lead or lead alloy to he impaired or destroyed by oxidation
during the process of charging, and without the production of a layer of lead-
sulphate between the lead or lead alloy and the lithanode in the operation of
discharging the element.
The weight of precious metal deposited may be very slight and the expense
attending its use in this way is consequently relatively small. Moreover the
precious metal may be deposited only on those portions of the strips or the like of
lead or lead alloy which are in close proximity to the lithanode element; the
remaining portions of the lead or lead alloy being protected by an insulating
cement.
11
In the manufacture of negative voltaic elements (positive electrodes in charging),
according to the method invented by Dr. Frankland F.R.S. and described in the
Specification of Letters Patent No. 10502 of 1886, a mould is employed in which
molten lead, or a molten alloy of lead and antimony, is cast around pellets, or small
pieces, of active material. This active material may be a compound produced by
mixing sulphuric acid with litharge, or red lead, or it may be the "lithanode
material, produced by the admixture of sulphate of lead, or of a solution of sulphate
of ammonia, with litharge, or it may be of partly, or fully, formed lithanode. The
high temperature of the molten metal is detrimental to the pellets, or small pieces,
of active material, and the contact between the solidified metal and the pellets, or
sinall pieces, of active material, is frequently imperfect both before, and sub-
sequently to, the charging of the plates. By this invention the pellets, or small
pieces, of active material are protected from the injurious effects of the high
temperature of the molten metal and a better contact is made between the solidified
metal and the pellets, or small pieces, of active material. In applying this
invention to these elements a thin strip of lead, or lead alloy, is coated with a thin
layer of gold, the coating being preferably effected by electro-deposition, and this
strip of lead, or lead alloy, so treated, is wrapped around the portions of the pellets,
or small pieces, of active material which would, otherwise, be brought into contact

page_text: 1
with the molten metal during the aforesaid casting process, the gilded surface of
the strip being in contact with the active material. The pellets, or small pieces, of
active material with the strips so applied thereto are placed in the mould and the
molten metal is cast around their edges according to Dr. Frankland's process.
Platinum may be used instead of gold, for coating the strip of lead, or lead alloy;
or a layer of platinum may be superposed upon a layer of gold.
Dated this 6th day of June 1891
J. H. JOHNSON & Co.,
47, Lincoln's Inn Fields, Agents.
COMPLETE SPECIFICATION.
Improvements in or connected with Negative Elements (Positive
Electrodes in Charging Secondary Cells) of Voltaic Batteries.
I, DESMOND GERALD FITZ-GERALD of 46 Loughborough Road Brixton in
the County of Surrey, Electrician, do hereby declare the nature of the said invention
and in what manner the same is to be performed to be particularly described and
ascertained in and by the following statement :-
Hitherto in utilizing the highly conductive slabs mainly composed of peroxide of
lead known under the name of "lithanode" it has been necessary to use a strip of
platinum or gold in order to establish electrical contact with the said "lithanode."
It has in fact been found (if we exclude the rarer metals belonging to the platinum
group) that platinum only will withstand prolonged use as an anode in the
electrolysis of dilute sulphuric acid. A practical contact with a plate of
lithanode can however be effected by means of a strip of gold held (as in the
case of the platinum strip) in close contact with the lithanode by means of a
strip of insulating material attached to the element by means of bolts and nuts
preferably of vulcanite. The cost of establishing contact in the manner described
by means of platinum or gold has been found so great as in many cases to be
prohibitive. According to this invention a thin layer of gold or of platinum or
thin layers of both is or are applied by electro-deposition or otherwise (for instance
by mercury gilding) upon the whole or a portion of a strip, tang, contact-piece or
washer of lead or lead alloy. The precious metal so applied to the lead or lead
alloy allows of the passage of the electric current from the lead strip or the like to
the lithanode or vice versa without allowing the lead or lead alloy to be impaired or
destroyed by oxidation during the process of charging and without the production
of a layer of lead-sulphate between the lead or lead alloy and the lithanode in the
operation of discharging the element. The quantity of precious metal deposited
may be very slight and the expense attending its use in this way is consequently
relatively small. Moreover the precious metal may be deposited only on those
portions of the strips or the like of lead or lead alloy which are in contact with the
lithanode element; the remaining portions of the lead or lead alloy being protected
by an insulating material.
The following is the manner in which my invention may be carried out in
practice. I prepare a solution of cyanide of gold in cyanide of potassium preferably
in the following manner. I dissolve 16 parts by weight of cyanide of potassium in
160 parts by weight of water, and, after raising the temperature of the solution to
140° Fahrenheit I electrolyse it by means of an anode of fine gold, of comparatively
large surface, and of a cathode of comparatively small surface, which may be of
gold or of any other metal, such as copper, which is not attacked by the cyanide
solution. The electrolysis is continued until about one part of gold has been
dissolved; the weight of this metal in solution being found by subtracting from
the weight lost by the anode the weight of gold recovered at the cathode. This
solution should be used at a temperature not under 140° Fahrenheit. Other well
known solutions for depositing "fine"gold may be employed; but I prefer to use
moderately dilute solutions at a high temperature. The surface of the strip, tang,

page_text: prepared for ging
by immersing it for a few seconds in dilute nitric acid, such as a mixture of one
part of the acid to ten parts of water and afterwards washing in water. If the
metal be bright it is usually advisable to immerse it in an alkaline solution before
dipping in acid, as in this case any greasy impurity would not be removed by the
latter. The density of current I prefer to use is from 02 to 08 ampère per square
inch of metallic surface to be gilt. The weight of gold deposited per square inch
may vary from one eightieth to one fifth of a grain per square inch. The total
weight in grains of the metal deposited may when the depositing current is known
be calculated from the following formula, in which is the total weight in
grains :
10 = ampère minutes
-
1.59
In lieu of gold, platinum may be deposited direetly upon the whole or a portion
of the strip, tang, contact piece or washer of lead or lead alloy. In this case the
platinating solution I prefer to use is made by dissolving platinic chloride in a
strong solution of potassic cyanide. With this a platinum anode exposing a large
extent of surface should be used. The deposition of platinum directly upon lead
or lead alloy is, however, on a large scale, somewhat difficult and uncertain; and
in practice I have found it preferable to deposit a thin film of gold upon the metal
before immersing it in the platinum bath, which in this case may be the well known
solution of roseleur.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performer, I declare that what I
claim is :-
:-
1. In or for use with negative elements (positive electrodes in charging
secondary cells) for voltaic batteries a conducting strip, tang, contact-piece, or
washer of lead or lead alloy having deposited or applied upon it or upon that
part of it which comes in contact with the lithanode or material of the element
a layer of gold or of platinum or of platinum upon gold substantially as herein-
before explained.
Dated this 7th day of March 1892.
J. H. JOHNSON & Co.,
Agents.