Improved Means for Effecting the Electro-chemical Generation of Chlorine in Metallurgical Operations for the Extraction of Gold from its Ores and for other Purposes.
Year: 1886

page_text: Date of Application, 4th Sept., 1886.
Complete Left, 4th June, 1887.
Complete Accepted, 22nd July, 1887.
Improved Means for Effecting the Electro-chemical Generation of
Chlorine in Metallurgical Operations for the Extraction of Gold
from its Ores and for other Purposes.
I DESMOND GERALD FITZGERALD of 6 Akerman Road Loughborough Road
Brixton in the County of Surrey Electrician do hereby declare the nature of this
invention to be as follows:-
The great difficulty in the electrolytic generation of chlorine, by the decomposition
under the influence of an electric current of hydrochloric acid or of an alkaline or
earthy chloride in solution, has been to find a suitable anode, unacted upon by the gas
in its nascent condition. One material only viz.: carbon, usually in the form known
as gas-carbon, has hitherto been available for use on a large scale in the above operation.
This material, however, is far from fulfilling the condition of being unacted upon,
chemically and mechanically, by the evolved chlorine. The ultimate disintegration
of the carbon anode, together with the difficulty of establishing efficient electrical
contact between fragments or plates of this material, has led to the failure in practice
of electrolytic processes for the extraction of the precious metals from their ores by
means of chlorine, and for the utilization of this element in various other directions.
Now I have found that peroxide of lead, in the form of dense conductive plates,
layers or masses, answers admirably the purpose of an anode for the electrolytic
generation of chlorine. Being already in the highest condition of oxidation, it is not
liable to further action in this direction, nor is it acted upon by the hypochlorites, or
liable to disintegration by the effect of the nascent chlorine evolved from its surface.
The only precaution I have in any case found necessary to ensure the permanency of
such plates, layers or masses when employed as anodes is, when free hydrochloric acid

page_text: is contained in the electrolyte, to avoid the prolonged contact of the peroxide with
this acid when the current is no longer passing.
"
In carrying my invention into effect for the purpose of extracting gold from its
ores and for other metallurgical purposes I usually construct anodes of large surface,
applied to and supported by a portion of the interior surface of an electrolytic tank,
in such manner that the ore to be treated may be in contact with the anode surface
and may thus be permeated by the evolved chlorine, when the anode is used for the
required purpose. In any case I employ in the construction of the anode a plastic
composition of oxide of lead (or of an equivalent insoluble compound of lead susceptible,
like the oxide, of being subsequently converted into peroxide of lead by electrolytic
action) in admixture with a solution, such as that of the sulphate or chloride of
ammonium, which will more or less gradually, and partially, react upon the lead
compound to produce a chemical change causing the composition to set "and to
acquire a high degree of solidity. I thus avoid any admixture with the lead compound
of inert material, such as plaster of Paris, or other cement, which would render
impossible the ultimate production of a highly-conductive mass of peroxide of lead.
I have constructed anodes wholly of this composition, applied by means of a trowel,
whilst yet freshly-mixed, to a portion of the interior surface of an electrolytic tank.
But by reason of the effects sometimes produced by the very considerable expansion
which occurs during its conversion into peroxide, I prefer to employ this composition
merely as a kind of mortar by means of which I build up the anode by uniting
together slabs, plates, fragments or granules of peroxide of lead, or of an insoluble
compound of lead more or less superficially converted into peroxide of lead.
The course I usually adopt, therefore, in the construction of anodes of large surface
is, first, to produce slabs, plates, "tiles" or granules of the compositions herein-
before described, by compressing in suitable moulds the freshly-mixed plastic mass
composed of oxide of lead (litharge) with (for instance) a half saturated solution of
sulphate of ammonia or with a solution of hydropotassic sulphate (sal enixum) or
hydrosodic sulphate, or by passing it through a sieve or granulating machine;
secondly to superficially convert the slabs, plates or granules when "set" or hardened,
into peroxide of lead, by the action of a hot solution of an alkaline or earthy
hypochlorite; thirdly to build up the anode, upon a suitable supporting surface, using
for this purpose, as a mortar or cement, the aforesaid plastic material in a freshly-
mixed condition, and, lastly, to effect a further conversion of the material into peroxide
of lead by the passage of a current through the mass when it has obtained a sufficient
degree of hardness and solidity. In effecting the electrolytic conversion last mentioned,
I prefer to employ as the electrolyte dilute sulphuric acid or a solution of the sulphate
of soda or of magnesia. Contact with the anode material may be obtained by means
of a plate of platinum embedded in the upper portion of the mass, and any suitable
cathode, such as a plate of copper, may be employed to complete the circuit of the
dynamo-machine or other source of electricity used to effect the conversion of the
material into peroxide. When this conversion has been effected to a sufficient extent,
i.c., when the whole surface of the anode has acquired a dark brown color and evolves,
in lieu of absorbing, the oxygen liberated by the passage of the current, the above
mentioned electrolyte may be replaced by the chloride solution to be employed in the
generation of chlorine.
I have given as an example one mode in which peroxide of lead may be utilised,
according to my invention for the electro-chemical generation of chlorine on a large
scale, and I have indicated the only known means, so far as I am aware, by which
indestructible anodes of this material-that is slabs, plates or masses, not liable to
disintegration, not in contact with any oxidisable (conducting) support, and possessing
a sufficiently high degree of conductivity to allow of the conducting support being
dispensed with may be readily obtained. But I do not confine myself to the above-
described mode of utilising peroxide of lead as an anode, which is convenient and
effective in the treatment of ores or compounds containing gold; nor do I limit
myself to the precise modes of obtaining peroxide of lead in a coherent form which

page_text: have been referred to. It is obvious that in the electro-chemical generation of chlorine
for bleaching purposes; or for the manufacture of hypochlorites or of chlorates, a
series of vertically disposed plates of peroxide of lead, alternating with cathode plates
of any suitable conducting material, may conveniently be employed. And it is
possible to obtain such plates by various means which, according to my experience,
are less convenient and effective than those which have been indicated above. Again,
it is not essential in all cases to obtain contact with the peroxide by means of platinum:
for instance the vertically-disposed plates just mentioned may be connected together
and with an external conductor by means of an alloy fusible at a comparatively low
temperature, such alloy being subsequently protected from electro-chemical action by
means of a layer of cement.
WM. BROOKES & SON,
55 & 56, Chancery Lane, London,
Agents for the said Desmond Gerald Fitzgerald.

page_text: Improved Means for Effecting the Electro-chemical Generation of
Chlorine in Metallurgical Operations for the Extraction of Gold
from its Ores, and for other Purposes.
I DESMOND GERALD FITZGERALD of 6 Akerman Road Loughborough Road Brixton
in the County of Surrey, 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:-
The great difficulty in the electrolytic generation of chlorine, by the decomposition
under the influence of an electric current of hydrochloric acid or of an alkaline or
earthy chloride in solution, has been to find a suitable anode, unacted upon by the
gas in its nascent condition. One material only, viz.: Carbon, usually in the form
known as gas-carbon, has hitherto been available for use on a large scale in the above
operation. This material, however, is far from fulfilling the condition of being
unacted upon, chemically and mechanically, by the evolved chlorine. The ultimate
disintegration of the carbon anode, together with the difficulty of establishing efficient
electrical contact between fragments or plates of this material, has led to the failure in
practice of electrolytic processes for the extraction of the precious metals from their
ores by means of Chlorine, and for the utilisation of this element in various other
directions.
Now I have found that peroxide of lead, in the form of dense conductive plates,
layers or masses, answers admirably the purpose of an anode for the electrolytic
generation of Chlorine. Being already in the highest condition of oxidation, it is not
fiable to further action in this direction; nor is it acted upon by the hypochlorites, or
liable to disintegration by the effect of the nascent chlorine evolved from its surface.
The only precaution I have in any case found necessary to ensure the permanency of
such plates, layers or masses when employed as anodes is, when free hydrochloric acid
is contained in the electrolyte to avoid the prolonged contact of the peroxide with
this acid when the current is no longer passing.
DESCRIPTION OF THE DRAWING.
In the accompanying drawing in section A A Tank of slate or of brick lined with
suitable material, B B anode of lead peroxide, C contact piece of platinum, DD cathode
of copper forming a tray of which the outer surface is coated with insulating material E
ore to be acted upon by chlorine, F electrolyte.
In carrying my invention into effect for the purpose of extracting gold from its ores
and for other metallurgical purposes, I usually construct anodes of large surface
applied to and supported by a portion of the interior surface of an electrolytic tank,

page_text: in such manner that the ore to be treated may be in contact with the anode surface,
and may thus be permeated by the evolved Chlorine, when the anode is used for the
required purpose. In any case I employ in the construction of the anode a plastic
composition of oxide of lead (or of an equivalent insoluble compound of lead
susceptible, like the oxide, of being subsequently converted into peroxide of lead by
set
"
rolytic action) in admixture with a solution, such as that of the sulphate or
chloride of ammonium, which will more or less gradually, and partially, react upon
the lead compound to produce a chemical change causing the composition to "
and to acquire a high degree of solidity. I thus avoid any admixture with the lead
compound of inert material such as plaster of Paris or other cement, which would
render impossible the ultimate production of a highly conductive mass of peroxide of
lead. I have constructed anodes wholly of this composition, applied by means of a
trowel, whilst yet freshly-mixed, to a portion of the interior surface (as shown in the
figure) of an electrolytic tank. But, by reason of the effects sometimes produced by
the very considerable expansion which occurs during its conversion into peroxide,
I prefer to employ this composition merely as a kind of mortar by means of which
I build up the anode by uniting together slabs, plates fragments or granules of
peroxide of lead, or of an insoluble compound of lead more or less superficially
converted into peroxide of lead.
The course I usually adopt, therefore, in the construction of anodes of large surface
is, first, to produce slabs, plates, "tiles" or granules of the composition hereinabove
described, by compressing, in suitable moulds, the freshly mixed plastic mass composed
of oxide of lead (litharge) with (for instance) a half-saturated solution of sulphate of
ammonia or with dilute sulphuric acid, or by passing it through a sieve or granulating
machine, secondly to superficially convert the slabs, plates or granules, when "set
or hardened, into peroxide of lead, by the action of a hot solution of an alkaline.or
earthy hypochlorite; thirdly to build up the anode, upon a suitable supporting surface,
using for this purpose, as a mortar or cement, the aforesaid plastic material in a
freshly-mixed condition; and lastly, to effect a further conversion of the material into
peroxide of lead by the passage of a current through the mass when it has obtained a
sufficient degree of hardness and solidity. In effecting the electrolytic conversion
last mentioned, I prefer to employ as the electrolyte dilute sulphuric acid or a solution
of the sulphate of soda or of magnesia. Contact with the anode material may be
obtained by means of a plate of platinum embedded in the upper portion of the mass;
and any suitable cathode, such as a plate of copper, may be employed to complete the
circuit of the dynamo-machine or other source of electricity used to effect the con-
version of the material into peroxide. When this conversion has been effected to a
sufficient extent, i.e. when the whole surface of the anode has acquired a dark brown
color, and evolves, in lieu of absorbing, the oxygen liberated by the passage of the
current, the above-mentioned electrolyte may be replaced by the chloride solution to
be employed in the generation of chlorine.
I have given as an example one mode in which peroxide of lead may be utilised,
according to my invention for the electro-chemical generation of Chlorine on a large
scale, and I have indicated the only known means, so far as I am aware by which
indestructible anodes of this material that is slabs, plates or masses not liable to
disintegration not in contact with any oxidisable, (conducting) support, and possessing
a sufficiently high degree of conductivity to allow of the conducting support being
dispensed with may be readily obtained. But I do not confine myself to the above-
described mode of utilising peroxide of lead as an anode, which is convenient and
effective in the treatment of ores or compounds containing Gold; nor do I limit
myself to the precise modes of obtaining peroxide of lead in a coherent form which
have been referred to. It is obvious that in the electro-chemical generation of
Chlorine for bleaching purposes, or for the manufacture of hypochlorites or of
chlorates, a series of vertically-disposed plates of peroxide of lead, alternating with
cathode plates of any suitable conducting material, may conveniently be employed.
And it is possible to obtain such plates by various means which, according to my

page_text: experience, are less convenient and effective than those which have been indicated
above. Again it is not essential in all cases to obtain contact with the peroxide by
means of platinum; for instance the vertically-disposed plates just mentioned may be
connected together and with an external conductor by means of an alloy fusible at a
comparatively low temperature, such alloy being subsequently protected from electro-
chemical action by means of a layer of cement.
Having now particularly described and ascertained the nature of my said Invention,
and in what manner the same is to be performed, I declare that what I claim is :-
The electro chemical generation of chlorine by means of an anode of peroxide of
lead in the form of dense highly-conductive layers, plates or masses of any required
form preferably obtained by the means hereinabove described; the said anode being
employed' in conjunction with any suitable cathode and with an electrolyte capable of
evolving chlorine.