and Apparatus for the Production of Zinc and Lead by Electrolysis of the Melted Chlorides.
Year: 1894

page_text: Date of Application, 24th Dec., 1894
Complete Specification Left, 27th Aug., 1895-Accepted, 9th Nov., 1895
PROVISIONAL SPECIFICATION
Process and Apparatus for the Production of Zinc and Lead by
Electrolysis of the Melted Chlorides.
I. Dr. RICHARD OTTOKAR LORENZ, Lecturer of Chemistry at the University
of Gottingen, Germany, do hereby declare the nature of this invention to be as
follows:-
My invention has for its object to effect a rational working of ores containing
zine nud lead, in particular of so called mixed ores, of residues or alloys containing
zinc and lead and the like This is effected by converting the compounds con-
taming zinc and lead into chlorides, which are subjected to an electiolytic process
under the influence of heat.
The production of the chlorides is effected according to the usual methods,
the use of which will of course depend upon the nature of the raw materials
treated.
When treating zine oies, lead ores and mixed zinc and lead ores, they are roasted
in the usual manner for conversion into oxides.
If the ones are mainly zinc ores, and consequently contain but little lead, and
possibly a small quantity of silver, cadmium &c. they are lixiviated directly with
hydrochloric acid of medium strength.
The lyes then contain mostly zinc chloride as also small quantities of chlorides
of lead, silver, cadmium &c. together with the calcium and ningnesium chlorides
that may be present.
If an excess of hydrochlone acid has been used, the lye will of course also
contain iron and aluminium chlorides.
As these latter would interfere with the electrolytic action, they are precipitated
by the addition of roasted ore or zinc residues. The lyes thus puiified ifter having
been clarified are evaporated to dryness and melted
If on the other hand the ores are mainly lead ores (either pure or containing
zine) and consequently conta'n so much lead that on lixiviating them by means of
bydrochloric acid insoluble lead chloride would be precipitated, the 1oasted material
is lixiviated with dilute acetic acid and hydrochloric acid gas 18 led through the
acetate solution, or concentrated acid is added thereto until the whole of the lead
and silver are precipitated as chloides. The clarified lyes are then decanted and
heated for the separation of iron and alumina, and then again clarified, and
decanted.
The discharged lyes, which again contam much free acetic acid, are used for the
lixiviation of fresh quantities of roasted one, and this process is repeated until all
the acetic acid has combined with zinc.
Foi regenerating the acetic acid, the zinc is made to combine with hydrochloric
acid gas introduced for that purpose, and the lye is then distilled to dryness The
distillate, condensed in the usual manner, now contains the whole of the acetic acid,
which can be used again for lixiviating of fresh quantities of roasted ore
It is evident that by a suitable mixture of the ores either before 10asting or after
roasting the one or the other process of lixiviation can be employed according as
circumstances may require.
When treating alloys or waste containing zinc and lead (such as zinc dust, zine
residues, muttle residues &c) the raw material is treated by the oue or the other
of the above described processes according to the composition thereof.

page_text: When zie chloride is treated such as is obtained as by product in various
technical processes such as in colour manufactories, it can be at orce melted and
subjected to electrolysis.
For carrying out the electrolytic process the apparatus shown diagrammatically
on the accompanying drawing can be advantageously used
Fig. 1 shows a sectional view of the apparatus,
Fig 2 shews the arrangement of the electrodes,
Fig. 3 a plan view of the cover and of the electrodes in which the connecting
plate for the electrodes is put away
In the inclined brickwork fiting chamber A is contained a vessel B for containing
the melted electrolyte. When constructed on a small scale this vessel may be
made of porcelain or of refractory clay containing a large percentage of kaolin and
as fiee as possible from on, when constructed on a large scale it is built up of
enamelled bucks which are bound together by a suitable binding material cousisting
manly of kaolin.
The vessel B of whatever material, is enclosed in an non casing b, for preventing
the penetration of combustion gases into the electrolyte.
For protecting the casing against the action of the combustion gases it can be
conted externally with clay and the like.
The vessel A is closed at top by means of a cover C of clay. For canying off
the gases formed by the electiolytic action a lateral tubular bianch D is provided
by means of which the gases are led into the earthenware pipe E in which they are
conducted to wherever required
At the lower end the vessel A 15 tapered to form a pocket G terminating in a
pipe F the end of which terminates in a discharging device II.
The section of the vessel B can be of any shape but should preferably be made
circular or elliptic. In the accompanying drawing an elliptic section has been
chosen as seen in Fig 3.
The electiodes are fixed in the cover C all chinks being hermetically sealed.
If the aforesaid chlorides are subjected to electrolysis in an impure state, for
mstance in case they should still contain a certain quantity of water or of organe
substances, such impurities will also be decomposed by the netion of the curent.
In that case besides the products resulting from the decomposition of the chloudes
other bodies and especially gases will be generated at both electrodes. It these
gases be permitted to intermingle in statu nascends it can easily happen that they
reunite in consequence of then natural affinity and the high temperature of the
electrolyte. Such reunion not only causes cxplosions within the electrolyte and in
consequence violent foaming, which much disturbs the regular process, but also a
not inconsiderable loss of energy because the bodies formed by the reunion of these
products, e principally hydrochloric acid and water are thus subjected to
electrolytic decomposition over and over again.
This difficulty is mainly overcome by the inelined position of the retort containing
the electrolyte and by the peculiar shape of the electrodes. The anode is placed
above the middle of the retort and the cathode below. Moreover both electrodes
ute so formed that the gas generated at the bottom side of the anode can ficely
pass thiongh or round to the upper side and that the metal precipitated at the
cathode can freely.sink, through or round the electrode to the bottom of the vessel.
This purpose is achieved by giving the electrodes the shape of a grating or network.
The accompanying drawing, Fig. 3 shows the electrodes composed each of three
carbon bars K K K and L L L of circular section. By these means, i e. the
inclined position of the retort and the grate shaped electrodes sufficient separation
of the products of decomposition is arrived at although the electrodes present a
considerable surfaco to each other and the distance between them is comparatively
small. The carbons K K K serve as anodes and L L L as cathodes
Through the branch can be introduced a porcelain tube M serving to charge
the vessel A with the melted electrolyte. The gases (chlorine) developed at the
appdes 18e up along the same, in consequence of the inclined position thereof, ia

page_text: the space R between the anodes and the sides of the vessel and pass through
branch D into the pipe E which leads then to wherever required.
At the cathodes K and K' the metal is separated in a molten condition and drips
in melted balls into the pocket G, where it is collected and discharged from time
to time.
The molten mass subjected to electrolysis always consists of a mixture of lead
chloride and zinc chloride, with or without addition of the other chlorides above
mentioned, of which silver chloride is of particular importance. According to its
ongin the zinc on the lead can predominate in the mass.
By means of the above described process of lixiviation by acetic acil it is no
doubt possible to separate the chlorides of zinc and lead from each other so that
the chl des of eel of the metals could be separately electrolysed.
But in most cases it has been proved ndvaulageous to subject a mixture of the
chlorides to electrolysis and, if the chlorides should have been obtained separately,
to mix them together before electrolysing them
The mass from the melting crucibles is either introduced liquid into the
decomposing furnace, or after cooling it can be introduced in pieces and melted
down therem at a modciate temperature. It is advantageous to fill the furnace to
about two thirds of its capacity.
In crying out the electrolysis a current having a tension of from 04 to 1 volts
is used Special attention reques to be paid during the process to the regulation
of the temperature. It must be kept above the melting point of the mixture of
zinc and lead chloides and of the zinc (or the lead) but below the boiling point
of the zinc chloride, that is to say, between the limits of 450° to 680° C
As soon as the entire mass is melted, the electric cuit is closed. The chlorine
developed at the anode rises us described and is led off by the pipe E It may be
suitably stored in gasholders, and can be utilised in any manner desned.
The metal separated at the cathode diops in spherical fouin from the same and
olls down into the pocket G whence it is tapped off.
During the electrolysis fresh material is introduced through the pipe M according
as the charge is consumed, so that the working is continuous.
During the electrolysis of the mass, the metals contumed therein do not separate
simultaneously but one after the other, the separation of the separated metals
being dependent upon the tension of the curent employed at the time as also upon
the proportion of the several constituents. This fact enables the fractional
separation to be effected, and consequently a separation of the several metals.
There will be fust sepurated silvei and then lead, but as the silver only exists in
small quantities and does not melt at the suitable temperature of 450 to 680° C,
the electrolysis is at the first stage of the process suitably conducted in such
manner that simultaneously with the silver a certum quantity of lead is separated,
which forms with the silver an easily fusible alloy. This alloy then drops from
the electiodes into the pocket
During this stage samples are advantageously frequently taken and ate examined
Ds to percentage of silver As soon as silver ceases to appear in apprecuble
quantities, the lead containing silver is tapped off. As a second fraction of the
electrolysis, pure lead is separated Alter tapping this off, the metal now
discharged consists of an alloy of the last rests of the lead with the other metals
present, with the exception of zinc. The electrolyte then only consists of pure
Zinc chloride, from which lastly chemically pure zine is obtained. The zine and
lead obtained by the electrolysis ane absolutely pare, that is to say of 100 per cent.
The periods of time within which the several factions are separated and
consequently the discharge must take place are determined by an analysis of the
particular product employed and depend upon the nature of the electrolite
During the process the tension of the cuntent is made to vary. For the
Eeparation of the lead a tension of 4 to 5 of a volt is sufficient. During the
separation of the zinc a tension of from 8 to 1 volt is employed.
In some cases it is desirable to regulate the electrolytic process. This is effected

page_text: by means of suitable additions which influence the melting temperature and the
conducting power of the electrolyte. As such additions, serve, among others,
sodium chloride, potassium chloride, magnesium chlonde, calcium chloride, sodium
Aluoride, fluorspai and the like.
Certain kinds of commercial zinc chloride, in particular such which proceed
from color manufactories, cannot be dehydrated alone by melting and contain in
addition to organic substances, in many cases, ammonium chloride If such zine
chlonde is subjected to electrolysis, then at the commencement thereof there will
escape, at both electrodes, gas, such as hydiogen, oxygen, chlorine, hydrochlouc
acid, ammonia, which cause an objectionable fiothing of the melt combined with
the defective separation of the metals For preventing this disadvantage, an
addition of litharge, red lead, zinc oxide and other metallic oxides oi superoxides
15 employed during the melting or before the commencement of electrolysis.
Dated this 24th day of December 1894.
ABEL & IMRAY,
Agents for the Applicant.
Process and Apparatus for the Production of Zinc and Lead by
Electrolysis of the Melted Chlorides.
I, Dr RICHARD OTTOKAR LORENZ, Lecturer of Chemistry at the University
of Gottingen, Germany, do hereby declare the nature of this mvention and in what
manner the same is to be performed, to be particularly described and ascertained
in and by the following statement
My invention has for its object to effect a rational working of ores containing
zinc and lead, in particular of so called mixed ores, of residues or alloys containing
zine and lead and the like. This is effected by converting the compounds
containing zinc and lead into chlorides, which are subjected to an electrolytic
process under the influence of heat.
The production of the chlorides is effected according to the usual methods, the
use of which will of course depend upon the name of the raw materials treated.
When treating zine ores, lead ones and mixed zinc and lend ores, they are roasted
in the usual manner for conversion into oxides
If the ores are mainly zinc oies, and consequently contain but little lead, and
possibly a small quantity of silver, cadium &c. they are lixiviated directly with
hydrochloric acid of medium strength.
The lyes then contam mostly zie chloide as also small quantities of chlorides
of lead, silver, cadmium &c. together with the calcium and magnesium chlorides
that may be present.
If an excess of hydrochlone neid has been used, the lye will of course also
contam on and aluminum chloides.
As these latter would interfere with the electiolytic action, they are precipitated
by the addition of roasted one or zinc residues The lyes thus purified after having
beca clarified are evaporated to dryness and melted.
I on the other hand the ones are mainly lead orcs (either pure of containing
ziuc) and consequently contain so much lead that on lixiviating them by means of
hydiochloric acid insoluble lead chloride would be precipitated, the roasted
material is lixiviated with dilute acetic acid and hydrochloric acid gas is led
through the acetate solution, or concentiated acid is added thereto until the whole
of the lead and silver are precipitated as chlondes. The clarified lyes are then
decanted and heated for the separation of non and alumina, and then again
clarihed, aud decanted.
The discharged lyes, which again contain much free acetic acid, are used for the

page_text: lixiviation of fresh quantities of roasted ore, and this process is repeated until all
the acetic acid has combined with zinc.
For regenerating the acetic acid, the zinc is made to combine with hydrochloric
acid gas introduced for that purpose, and the lye is then distilled to dryness. The
distillate, condensed in the usual manner, now contains the whole of the acetic acid,
which can be used again for lixiviating of fresh quantities of toasted ore.
It is evident that by a suitable mixture of the oies either before 10asting or after
roasting the one or the other process of lixiviation can be employed according as
circumstances may require.
When treating alloy's or waste containing zinc and lead (such as zine dust, zinc
residues, muffle residues &c.) the law material is ticated, by the one of the other
of the above described processes according to the composition thereof.
When zinc chloide is treated such as 13 obtained as by product in various
technical processes, such as in colour manufactories, it can be at once melted and
subjected to electrolysis.
Foi cariying out the electrolytic process the apparatus shewn diagrammatically
on the drawing accompanying my Piovisional Specification can be advantageously
used.
Fig. 1 shows a sectional view of the apparatus
Fig. 2 shews the arrangement of the electrodes,
Fig. 3 a plan view of the cover and of the electrodes in which the connecting
plate for the electrodes 18 put away.
In the inclined brickwork filing chamber A is contained a vessel B for containing
the melted electrolyte When constructed on a small scale this vessel may be made
of porcelain or of refiactory clay containing a large percentage of kaolin and as
free as possible from ion, when constructed on a large scale it is built up of
enamelled bricks which are bound together by a suitable binding material consisting
mainly of kaolin.
The vessel B of whatever material, 19 euclosed in an iron casing b, for preventing
the penetration of combustion gases into the electrolyte.
For protecting the casing b against the action of the combustion gases it can be
coated externally with clay and the like
The vessel B is closed at top by means of a cover of clay. For carrying off
the gases formed by the electrolytic action a lateral tubular branch D 15 provided
by means of which the gases are led into the earthenware pipe E in which they are
conducted to wherever required
At the lower end the vessel B is tapered to form a pocket G terminating in a
pipe F the end of which terminates in a discharging device H
The section of the vessel B can be of any shape but should preferably be made
cucular o elliptic In the drawing an elliptic section has been chosen as seen
in Fig. 3.
The electrodes are fixed in the covei C all chinks being hermetically sealed.
If the aforesaid chlorides are subjected to electrolysis in au impure state, for
instance in case they should still contain a certain quantity of water or of organic
substances, such impurities will also be decomposed by the action of the current.
In that case besides the products resulting from the decomposition of the chloudes
other bodies and especially gases will be generated at both electrodes. If these
gases be permitted to intermingle in statu nascends it can easily happen that they
eunite in consequence of thoir natural afhuity and the high temperature of the
electrolyte. Such reunion not only causes explosions within the electrolyte and in
consequeuce violent foaming, which much disturbs the regular process, but also a
not considerable loss of energy because the bodies formed by the reunion of
these products i.e. principally hydrochloric acid and water are thus subjected to
electrolytic decomposition over and over again
This difficulty is mainly overcome by the inclined position of the retort containing
the electrolyte and by the peculiar shape of the electrodes The anode is placed
above the middle of the retort and the cathode below.

page_text: Moreover both electrodes are so formed that the gas generated at the bottom
sde of the anode can freely pass through or round to the upper side and that the
metal precipitated at the cathode can fieely sink, through or round the electrode to
the bottom of the vessel This purpose is achieved by giving the electrodes the
shape of a grating of network
In the drawing, Fig. 2 shews the electrodes composed, each of three carbon
bars K K K and L L L of cu cular section. By these means, .e. the inclined
position of the retort and the encular shape of the electrodes sufficient separation
of the products of decomposition 18 arrived at although the electrodes present a
considerable surface to each other and the distance between them is comparatively
nal. The carbons K K K serve as anodes and I, L' L' as cathodes.
Through the branch D can be introduced a porcelain tube M serving to charge
the vessel A with the melted electrolyte. The gases (chlorino) developed at the
anodes use up along the same, in consequence of the inclined position thereof, in
the space R between the anodes and the sides of the vessel and pass through
branch D into the pipe E which leads them to wherever required.
At the cathodes L L L the metal is separated in a molten condition and diips in
melted balls into the pocket. G, where it is collected and discharged from time to time.
The molten mass subjected to electrolysis always consists of a mixture of lead
chloride and zinc chloride, with or without addition of the other chlorides above
mentioned, of which silver chloride is of particular importance. According to its
origin the zinc or the lead cau predominate in the mass.
By means of the above described process of lixiviation by acetic acid it is no
doubt possible to separate the chloinles of zinc and lead from each other so that
the chloides of each of the metals could be separately electrolysed.
But in most cases it has been proved advantageous to subject a mixture of the
chlorides to electrolysis and, if the chlorides should have been obtained separately,
to mix them together before electrolysing thein.
The mass from tho melting crucibles is either introduced liquid into the
decomposing furnace, or after cooling it can be introduced in pieces and melted down
therein at a moderate temperature
It is advantageous to fill the furnace to
about two thirds of its capacity.
In carrying out the electrolysis a current having a tension of from 0.4 to 1 volts
16 used.
Special attention requires to be paid dang the process to the regulation of
the temperature. It must be kept above the melung point of the mixture of zinc
and lead chlorides and of the zic or the lead) but below the boiling point of the
zinc chloride, that is to say, between the limits of 450° to 680° C.
As soon as the entire mass is melted the electric cncunt is closed. The chloimme
developed at the anode ses as described and is led off by the pipe E
suitably stored in gasholders, and can be utilised in any manner desued.
It may be
The metal separated at the cathode drops in spherical form from the same and
rolls down into the pocket G whence it is tapped off.
During the electrolysis fresh material is introduced through the pipe M according
as the charge is consumed, so that the working is continuous.
Dung the electrolysis of the mass, the metals contained therein do not separate
smultaneously but one after the other, the separation of the separated metals being
dependent upon the tension of the curent employed at the tinie as also upon the
proportion of the several constituents. This fact enables the fractional separation
to be eflected, and consequently a separation of the several metals.
There will be first separated silver, and then lead, but as the silver only exists in
small quantities and does not melt at the suitable temperature of 150° to 680° C,
the electrolysis is at the first stage of the process conducted with an electrical
current of such pressure that simultaneously with the silver a certain quantity of
lead is separated, which forms with the silver an easily fusible alloy. This alloy
then drops from the electiodes into the pocket.

page_text: During this stage samples are advantageously frequently taken and are examined
as to percentage of silver. As soon as silver ceases to appear in appreciable
quantities, the lead containing silver is tapped off'; as second fraction of the
electrolysis, pe lead is separated. After tapping this off, the metal now discharged
consists of an alloy of the last remainders of the lead with the other metals present,
with the exception of zine. The electrolyte then only consists of pure zinc chloride,
from which lastly chemically pune zine is obtained. The zin and lead obtained by
the electrolysis are absolutely pure, that is to say of 100 per cent.
The periods of time within which the several fractions are separated and co-
sequently the discharge must take place, are determined by an analysis of the
particular product employed and depend upon the nature of the electrolyte
Doing the process the tension of the current is made to valy. For the
separation of the lead a tension of 4 to 5 of a volt is sufficient
separation of the zine a tension of from 8 to 1 volt is employed.
During the
In some cases it is destable to regulate the electrolytic process. This is offected
by means of suitable additions which influence the melting temperature and the
conducting power of the electrolyte A such additions, serve, among others,
sodium chloride, potassium chloride, magnesium chloride, calcium chloride, sodium
fluoride, noispai aud the like, in proportions which have tu euch case to be
determined by experiment.
Certain kinds of commercial zinc chloride, in particular such which proceed from
colom manufactories, cannot be dehydrated alone by melting aud contain in
addition to organic substances, in many cases, ammonium chloride. If such ZIC
chloride is subjected to electrolysis, then at the commencement thereof there will
escape, at both electrodes, gas, such as hydrogen, oxygen, chlorine, hydrochloric
acid, ammonia, which cause an objectionable fiothing of the melt combined with
the defective separation of the inetals. For preventing this disadvantage, nu
addition determined by experiment in each case of litharge, red lead, zinc oxide
aud other metallic oxides or superoxides is employed during the melting on before
the commencement of electrolysis.
Having now particularly described and ascertained the natie of this mven-
tion and in what manner the same is to be performed, I declare that what I
claim is
1. The process for obtaining metallic zinc and lead by subjecting the chlorides
thereof to fractional electrolysis at a temperature of from 450° to 680° C.,
substantially as described.
2. In the process referred to in the first claim, the addition of small quantities
of lithage, red lead, superoxide of lead, zinc oxide, or other metallic oxides or
superoxides, or of common salt, potassium chloride, magnesium chloride, calcium
chloride, calcium fluoride, sodium fluoride or similar fluxes for preventing fothing,
and for regulating the temperature, conductivity and volatilisation of the molten
mass duing the electrolysis, substantially as described.
3. In the process referred to in the first claim, the production of the chlorides
to be subjected to electrolysis by the lixiviation of ores or residues of all kinds
containing zinc and lead by means of hydrochloric acid or acetic acid, with
precipitation, if required, of the lead and silver chlorides by the addition of
concentrated hydrochlouc acid or introduction of hydrochloric acid gas sub-
stantially as described.
Apparatus for caying out the process referred to in the first and second
claims, consisting of an inclined retort or vessel such as B of porcelain, fireclay or
other suitable material provided with a suitable charging device M a discharging
device DE for the gases generated, as also at the lower end a discharging
device H, and preferably provided with an iron casing b, the said retort or vessel
being furthermore provided with a cover C closing the same, and any desned
number of electrodes K K K L L' L' fitted airtight into the cover, substantially
as described.

page_text: 5. In combination with the apparatus substantially described in Claim 4, a pair
of electrodes shaped so as to prevent the products of electrolysis precipitated on
them from accumulating on the surfaces facing each other.
Dated this 27th day of August 1895.
ABEL & IMRAY,
Agents for the Applicant.