Improvements in the Production of Chlorine, in the Purification of Lead, in the Recovery of Precious or other Metals with which or Apparatus the Lead may be Associated, and in Means employed therein.
Year: 1891

page_text: Date of Application, 8th Dec., 1891
Complete Specification Left, 10th Oct., 1892-Accepted, 26th Nov., 1892
5
PROVISIONAL SPECIFICATION.
Improvements in the Production of Chlorine, in the Purification of
Lead, in the Recovery of Precious or other Metals with which
or Apparatus
the Lead may be Associated, and in Means
employed therein.
J
I. FARNHAM MAXWELL LYTE of 60, Finborough Road, London, Analytical
Chemist, do hereby declare the nature of this invention to be as follows:-
This invention relates mainly to a process of conjointly producing chlorine and
purifying lead and also recovering precious or other metals with which the lead
may be associated...
1
The principal object is to recover chlorine from native chlorides or from chlorides
which are artificially produced or are the result of commercial manufactures (the
cálcic chloride' of the ammonia-soda process for example) or from commercial
hydrochloric acid (produced by the Leblanc process or by any process by
which commercial hydrochloric acid may be obtained from a native or other
chloride or from an oxychloride) by the decomposition of such chloride or acid
with the formation of a chloride of the metal to be purified followed by the
fusion of the said chloride so formed and by its electrolytical decomposition whilst
in the fused 'state' into a metal and chlorine. 1.
'
I will 'take the purification of lead and the recovery of silver therefrom as an
example, inasmuch as the ordinary methods for the purification of lead are
expensive and because :-
(1) lead is a metal commercially obtainable for purification commercially on a
large scale near t
I
(2) lead is easily oxidized and consequently easily forms soluble salts from
which the silver and most other metals can be easily.extracted
1.
(3) plumbic chloride being but little soluble precipitates easily from the mother
liquors
140)
.
(4) plumbic chloride is fusible at a comparatively low temperature
(5)t is electrolytically decomposable by a current of low voltage and
.
(6) the metal lead' which is the result of this decomposition also fuses at a
temperature sufficiently low to enable it to be syphoned off.
Assuming a native chloride to be used, chloride of sodium for instance, this may
be treated by the ordinary Leblanc process. Or assuming an artificial chloride,
such as the calcic chloride of the ammonia-soda process, to be used this may be
"treated by any of the known methods, such as those specified by Weldon,
"Eschelmann; Lyte & Steinhart, and others, for the production of commercial
"hydrochloric acid. Or assuming the chloride, native or artificial, to be a magnesic
chloride this also may be treated by any of the known methods for obtaining
commercial hydrochloric acid. With this commercial hydrochloric acid, whether
produced from any of the sources or in any of the ways above referred to, or in any
other commercial way, a chloride of the metal to be purified may be produced in
one of the ways hereafter described.
1
"Assuming then lead to be the metal to be purified the chloride of lead will be
produced as follows:-
OVO S (a). By boiling hydrochloric acid with plumbic monoxide, decanting and
cooling the liquor to crystallize out the plumbic chloride the mother liquor
being evaporated down and used over again with fresh acid for treating a
"fresh batch of plúmbic oxide.
.
(b). By adding the hydrochloric acid to a solution of a lead salt such as the
nitrate or acetate of lead wherefrom the plumbic chloride is precipitated,

page_text: the mother liquor being decanted off and used for the further production of
the soluble lead salt which may be evaporated down to the required strength
for use over again. A convenient way to make the lead nitrate or acetate is by
wetting granulated lead (which is at the same time exposed to the air) with
the dilute nitric or acetic acid whereupon the lead oxidises and the oxide is
dissolved by the acid whilst any silver present which may enter into solution
may here be recovered by means of finely divided metallic lead for instance.
Or the plumbic acetate or nitrate may be made by dissolving lead oxide in
nitric or acetic acid.
Where plumbic acetate is employed for the production of plumbic chloride a
mode of working to be recommended but which I do not wish to limit myself to, is
as follows: Suppose one commences with a 25% solution of plumbic acetate.
Granulated or other finely divided lead is to be alternately wetted with this and
exposed to the air so long as the solution continues to increase in density. It is
then allowed to settle and the clear liquor drawn off. This liquor may be. divided
into two equal portions. One may be completely or nearly completely precipitated
as plumbic chloride by an addition of hydrochloric acid, the solution separated
from the precipitate, neutralised or rendered slightly basic by the addition of the
second portion of the liquor, and finally concentrated if requisite. The operation
may be recommenced by passing the solution over the metallic lead as before so
that it may take up more base and so on, etc. As plumbic chloride may by this
method still be slightly basic it may be treated with a little dilute hydrochloric
acid after which it may be finally washed and dried.
(c). By alternately adding hot dilute hydrochloric acid to granulated lead and
exposing the latter to the air repeatedly, the lead chloride formed in the liquor
separating out on cooling.
The plumbic chloride obtained in any of the above ways having been collected
(washed if necessary) and dried is to be fused in a crucible or other suitable vessel
and submitted to electrolysis whilst in the fused condition in the manner hereafter
described.
The electrolytic decomposition cell may be a trough of any suitable material say
of earthenware or of enamelled iron and it may be heated in a sand or air bath or
directly by gas or other means whereby it may be maintained at a constant
temperature. In this vessel or cell are to be placed a number of plates corrugated
if desired say of carbon graphite or other suitable material unattackable by chlorine
and unaffected by the fused plumbic chloride in which they are immersed said plates
being alternately anodes and cathodes, or the cell may be otherwise arranged.
Two or more such cells may be used grouped if desired in series, the anode of the
one cell being coupled to the cathode of the other cell whereby a more economical
production of chlorine may be obtained than by the employment of a single cell.
This trough is closed by a convenient cover sealed (say by means of a liquid joint)
to avoid loss of chlorine, a pipe being connected thereto to convey away the chlorine.
The electrodes are so supported in the trough that they do not touch one another
or the metallic lead which collects on the bottom of the trough sufficient space being
left for the said metallic lead (resulting from the electrolytic decomposition of the
fused chloride) to flow beneath them without touching and so short circuiting them
the bottom of the trough sloping down to one end where the molten metallic lead
will collect and whence it may be caused to run off spontaneously by means of a
syphon or other means. The trough may be heated in a sand bath but this although
often advantageous to equalise the heat is not necessary as the trough may be
directly heated by gas-jets beneath it. The plates pass through slots in the cover
of the trough with which they make gas-tight joints. They do not extend the full
width of the trough in order to allow the chlorine generated to flow past them to
the outlet pipe or a passage for the chlorine by perforations or otherwise forming
gaps at the upper part of the plates, and they are provided with external binding
clips by which they are coupled respectively to the anode and cathode conductors.
Instead of the plates passing through the cover they may be attached to the

page_text: underside thereof by any suitable means, their terminals only passing through for
connection with the main conductors. Or the plates might be supported in grooves
in the sides of the trough and connected inside the trough the anode and cathode
plates respectively with one anode and one cathode terminal passing through the
cover, the electrical connections being suitably protected against the action of the
chlorine. Instead of arranging the anodes and cathodes alternately all the plates
in one half of the trough may be anodes and all in the other half cathodes with
one terminal to each group of anodes and cathodes passing through the cover.
The overflow siphon may be made of earthenware or iron enamelled externally,
the bend of the overflow pipe being at such a height that the level of the molten
lead will remain constant provided the fused chloride is kept at the same level.
Suitable provision should therefore be made for supplying the chloride to the tank
without removing the cover, say by means of a pipe passing through the cover
and sealed by dipping into the molten chloride thus preventing the escape of
chlorine.
The arrangement of the cell may also be further varied for instance by omitting
the cathode plates and making the molten lead the cathode in which case sufficient
lead for the purpose should be put into the trough at the outset enough always
being retained to form a cathode of extended area, the conductor connected with
the negative terminal of the source being in that case made of some suitable material
preferably of iron tinned or leaded to ensure good electrical contact with the molten
lead in which it is immersed.
Owing to the low resistance of fused lead chloride a large current of low voltage,
say five to two volts or less, may be employed lead chloride being decomposable
by a current from even one Laniell cell which has an E.M.F. of little over one
volt, the conductors and dynamo being similar to those used in electro-plating.
The conductibility and strength of the carbon electrodes may be much improved
by making them with a core of iron or some other suitable metal in the form of a
plain or corrugated or perforated plate or of wire or gauze surrounded by a covering
of dense carbon whereby while the metal is protected from contact with the fused
chloride the thickness of carbon to be traversed by the electric current is much
diminished.
The metallic lead resulting from the electrolytical decomposition of the plumbic
chloride may be granulated and converted into a salt of lead as above described or
may be oxidized into massicot for conversion into fresh plumbic chloride.
Dated this 8th day of December 1891.
F. MAXWELL
By A. M. & Wm. Clark,
53, Chancery Lane, London, Chartered Patent Agents.
COMPLETE SPECIFICATION.
Improvements in the Production of Chlorine, in the Purification of
Lead, in the Recovery of Precious or other Metals with which
the Lead may be Associated, and in Means or Apparatus
employed therein.
I, FARNHAM MAXWELL LYTE of 60, Finborough Road, London, Analytical
Chemist, 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 :-
This invention relates mainly to a process of conjointly producing chlorine and
purifying lead and also recovering precious or other metals with which the lead
may be associated.
The principal object is to recover chlorine from native chlorides, or from
chlorides which are artificially produced, or are the result of commercial manu-
factures (the calcic chloride of the ammonia-soda process for example) or from

page_text: commercial hydrochloric acid (produced by the Leblanc process, or by any process
by which commercial hydrochloric acid may be obtained from a native or other
chloride or from an oxychloride) by the decomposition of such chloride or acid with
the formation of a chloride of the metal to be purified, followed by the fusion of the
said chloride.so formed and by its electrolytical decomposition whilst in the fused
state into a metal and chlorine.
I will take the purification of lead and the recovery of silver therefrom as
an example, inasmuch as the ordinary methods for the purification of lead are
expensive and because
.
(1) lead is a metal commercially obtainable for purification commercially on a
large scale ;
(2) lead is easily oxidised and consequently easily forms soluble salts from
which the silver and most other metals can be easily extracted;
(3) plumbic chloride being but little soluble precipitates easily from the mother
liquors;
(4) plumbic chloride is fusible at a comparatively low temperature;
(5) plumbic chloride is electrolytically decomposable by a current of low
voltage ;. and
(6) the metal lead which is the result of the decomposition of plumbic chloride
also, fuses at a temperature sufficiently low to enable it to be syphoned off.
Assuming a native chloride to be used, chloride of sodium for instance, this may
be treated by the ordinary Leblanc process for the production of commercial
hydrochloric acid. Or assuming an artificial chloride, such as the calcic chloride of
the ammonia-soda process, to be used this may be treated by any of the known
methods, such as those specified by Weldon, Eschelmann, Lyte and Steinhart, and
others, for the production of commercial hydrochloric acid. Or assuming the
chloride, native or artificial, to be a magnesic chloride, this also may be treated by
any of the known methods for obtaining commercial hydrochloric acid.
With this
commercial hydrochloric acid, whether produced from any of the sources or in any
of the ways above referred to, or in any other commercial way, a chloride of the
metal to be purified may be produced in one of the ways hereafter described.
Assuming, then, lead to be the metal to be purified, the chloride of lead will be
produced as follows:-
:-
(a) By boiling hydrochloric acid with plumbic monoxide, decanting, pre-
cipitating out the silver with spongy or finely divided metallic lead, decanting
and cooling the liquor to crystallize out the plumbic chloride, the mother
liquor being evaporated down and used over again with fresh acid for treating
a fresh batch of plumbic oxide;
(b) By adding the hydrochloric acid to a solution of a lead salt such as the
nitrate or acetate of lead wherefrom the plumbic chloride is precipitated, the
mother liquor being decanted off and used for the further production of
the soluble lead salt which may be evaporated down to the required strength
for use over again. A convenient way to make the lead nitrate or acetate
is by wetting granulated lead (which is at the same time exposed to the air)
with the dilute nitric or acetic acid whereupon the lead oxidises and the
oxide is dissolved by the acid, the silver precipitating out by contact with
the metallic lead. Or the plumbic nitrate.or. acetate may be made by
dissolving lead oxide in nitric or acetic acid whilst any silver present which
may enter into solution may here be recovered by means of spongy or finely
divided metallic lead.
"
Where plumbic acetate is employed for the production of plumbic chloride a
mode of working.to. be recommended but, which I do not wish to limit myself to, is
as follows: Suppose one commences with a 25% solution of plumbic acetate.
Granulated or other finely divided lead is to be alternately, wetted with this, and
exposed to the air so long as the, solution continues to increase in density... It is
then allowed to settle and, the clear liquor drawn off. This liquor may be divided
into two equal portions. One may be completely, or nearly completely, precipitated

page_text: as plumbic chloride, by an addition of hydrochloric acid, the solution separated from
the precipitate, neutralised or rendered slightly basic by the addition of the second
portion of the liquor, and finally concentrated if requisite. The operation may be
recommenced by passing the solution over the metallic lead as before so that it may
take up more base and so on, etc. As plumbic chloride may by this method still be
slightly basic, it may be treated with a little dilute hydrochloric acid, after which
it may be finally washed and dried.
(c) By alternately adding hot dilute hydrochloric acid to granulated lead and
exposing the latter to the air, repeatedly extracting the silver by the
addition of finely divided metallic or spongy lead to the solution and
separating the lead chloride formed and dissolved in the liquor by cooling.
The plumbic chloride obtained in either of the above ways having been collected
(washed if necessary) and dried, is to be fused in a crucible or other suitable vessel
and submitted to electrolysis whilst in the fused condition in the manner hereafter
described.
The electrolytic decomposition cell may be a trough t, as represented in the
accompanying drawing, of any suitable material, say of glazed earthenware or of
enamelled iron, and it may be heated in a sand or air bath or directly by gas or
other means whereby it may be maintained at a constant temperature. In this
vessel or cell are to be placed a number of plates a, c, (corrugated if desired) say of
carbon graphite or other suitable material unattackable by chlorine and unaffected
by the fused plumbic chloride in which they are immersed, said plates being
alternately anodes and cathodes, or the cell may be otherwise arranged. Two or
more such cells may be used, grouped if desired in series, the anode of the one cell
being coupled to the cathode of the other cell whereby a more economical pro-
duction of chlorine may be obtained than by the employment of a single cell. This
trough is closed by a convenient cover sealed (say by means of a liquid joint) to
avoid loss of chlorine, a pipe being connected thereto to convey away the chlorine.
The electrodes are so supported in the trough that they do not touch one another
or the metallic lead which collects on the bottom of the trough, sufficient space
being left for the said metallic lead (resulting from the electrolytic decomposition
of the fused chloride) to flow beneath them without touching and so short circuiting
them, the bottom of the trough sloping down to one end where the molten metallic
lead will collect and whence it may be caused to run off spontaneously by means of
a syphons or other means. The trough may be heated in a sand bath, but this
although often advantageous to equalize the heat is not necessary as the trough
may be directly heated by gas-jets beneath it. The plates may pass through slots
in the cover of the trough with which they make gas-tight joints. They do not
extend the full width of the trough in order to allow the chlorine generated to flow
past them to the outlet pipe, or a passage for the chlorine by perforations or other-
wise forming gaps at the upper part of the plates, and they are provided with
external binding clips by which they are coupled respectively to the anode and
cathode conductors. Instead of the plates passing through the cover, they may be
attached to the underside thereof by any suitable means, their terminals only passing
through for connection with the main conductors. Or the plates might be supported
in grooves in the sides of the trough and connected inside the trough, the anode and
cathode plates respectively with one anode and one cathode terminal passing
through the cover, the electrical connection being suitably protected against the
action of the chlorine. Instead of arranging the anodes and cathodes alternately,
all the plates in one half of the trough may be anodes and all in the other half
cathodes with one terminal to each group of anodes and cathodes passing through
the cover.
The overflow siphon may be made of earthenware or iron enamelled externally,
the bend of the overflow pipe being at such a height that the level of the molten
lead will remain constant provided the fused chloride is kept at the same level.
Suitable provision should therefore be made for supplying the chloride to the tank
without removing the cover, say by means of a pipe p passing through the cover

page_text: and sealed by dipping into the molten chloride, thus preventing the escape of
chlorine.
The arrangement of the cell may also be further varied for instance by omitting
the cathode plates and making the molten lead the cathode in which case sufficient
lead for the purpose should be put into the trough at the outset, enough always
being retained to form a cathode of extended area, the conductor connected with
the negative terminal of the source being in that case made of some suitable
inaterial, preferably of iron tinned or leaded, to ensure good electrical contact with
the molten lead in which it is immersed.
Owing to the low resistance of fused lead chloride a large current of low voltage,
say five to two volts or less, may be employed, lead chloride being decomposable
by a current from even one Laniell cell which has an E.M.F. of little over one
volt, the conductors and dynamo being similar to those used in electroplating.
The conductibility and strength of the carbon electrodes may be much improved
by making them with a core of iron or some other suitable metal in the form of a
plain or corrugated or perforated plate, or of wire or gauze surrounded by a
covering of dense carbon whereby while the metal is protected from contact with
the fused chloride the thickness of carbon to be traversed by the electric current is
much diminished.
The metallic lead resulting from the electrolytical decomposition of the plumbic
chloride may be granulated and converted into a salt of lead as above described, or
may be oxidised into massicot for conversion into fresh plumbic chloride.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is―
1. The herein described process of conjointly producing chlorine, purifying lead,
and recovering precious or other metals associated therewith, which consists in
producing commercial hydrochloric acid in any known way, either from a native or
artificial or waste chloride, forming plumbic chloride therewith in one of the ways
herein described, fusing the chloride thus produced and decomposing it
electrolytically when in the fused state in the manner and by the means specified.
2. The herein described process of conjointly producing chlorine, purifying lead,
and recovering precious or other metals associated therewith, which consists in
producing commercial hydrochloric acid in any known way, either from a native or
artificial or waste chloride, forming therewith plumbic chloride by boiling the
hydrochloric acid with plumbic monoxide, extracting the silver with finely divided
or spongy lead, crystallizing out the plumbic chloride, fusing it and decomposing it
electrolytically when in a fused state in the manner and by the means specified.
3. The herein described process of conjointly producing chlorine, purifying lead,
and recovering precious or other metals associated therewith, which consists in
producing commercial hydrochloric acid in any known way, either from a native or
artificial or waste chloride, forming therewith plumbic chloride by precipitating_a
soluble salt of lead with the hydrochloric acid (the soluble salt having been made
and the silver precipitated in the manner herein specified) fusing the plumbic
chloride thus produced and decomposing it electrolytically when in a fused state, in
the manner and by the means specified.
4. The herein described process of conjointly producing chlorine, purifying lead,
and recovering precious or other metals associated therewith, which consists in
producing commercial hydrochloric acid in any known way, either from a native or
artificial or waste chloride, forming therewith plumbic chloride by repeatedly and
alternately adding the hot dilute hydrochloric acid to granulated lead and exposing
the latter to the air, extracting the silver by the addition of finely divided metallic
or spongy lead to the solution, crystallizing out the plumbic chloride, fusing it
and decomposing it electrolytically, in the manner and by the means herein
specified.
5. In the herein described process of conjointly producing chlorine, purifying

page_text: lead, and recovering precious or other metals associated therewith, the employment
of the herein described apparatus for the electrolytical decomposition of fused
plumbic chloride, consisting of the closed electrolytic trough containing electrodes,
as described, heated externally and provided with means for supplying the chloride
to be decomposed, carrying off the chlorine and withdrawing the fused lead.
Dated this 10th day of October 1892.
F. MAXWELL LYTE,
By A. M. & Wm. Clark,
53, Chancery Lane, London, Chartered Patent Agents.