4,085,027 Hybrid bipolar electrode

Patent Number/Link:

14 Claims, 6 Drawing Figures

3,873,437 3/1975 Pulver 204/254

3,884,792 5/1975 McGilvery 204/268

3,910,827 10/1975 Raetzsch et a1. 204/98

Primary Examiner-F.C. Edmundson

Attorney, Agent, or FYrm-William G. Addison

An improved hybrid bipolar electrode particularly useful

in an alkali chloride electrolysis application, having

an anodic member and cathodic member connected in

spaced apart relationship by a fastener assembly, a seal

being formed between portions of the anodic member

and the cathodic member to substantially seal electrolyte

from the space between the anodic member and the

cathodic member. In one aspect, a barrier member is

interposed between the anodic member and the cathodic

member to inhibit the contact of migrating

atomic hydrogen with the anodic member. In one other

aspect of the present invention, a portion of the fastener

assembly is constructed of an electricaIly conductive

material and electrical continuity is established between

the anodic member and the cathodic member via the

fastener assembly, the barrier member serving to effectuate

a more even distribution of current flow between

the cathodic member and the anodic member in yet

another aspect of the present invention.

United States Patent (19]

Poush et al.

[54] HYBRID BIPOLAR ELECfRODE

[75] Inventors: Kenneth A. Poush, Lake Jackson,

Tex.; James E. Reynolds, Golden,

Colo.

[73] Assignee: Kerr-McGee Chemical Corporation,

Oklahoma City, Okla.

[21] AppI. No.: 545,016

[22] Filed: Jan. 29, 1975

[51] Int. Cl,2 e25B 9/00; C25B 11/00;

C25B 13/00; C25B 1/34

[52] U.S. Cl 204/268; 204/254;

204/286

[58] Field of Search 204/286, 268, 254, 255,

204/256

[56] References Cited

U.S. PATENT DOCUMENTS

806,413 12/1905 Kother 204/268

3,242,065 3/1966 Nora et a1. 204/255

3,312,614 4/1967 Schick 204/255

3,389,071 6/1968 Meyers 204/268

3,402,117 9/1968 Evans 204/286

3,752,757 8/1973 Stephenson et a1. 204/256

3,759,813 9/1973 Raetzsch et a1. 204/256

3,813,326 5/1974 Gunby 204/268

3,824,173 7/1974 Bouy et aI 204/284

3,859,197 1/1975 Bouy et aI 204/284

[57]

[11]

[45]

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4,085,027

Apr. 18, 1978

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SUMMARY OF THE INVENTION

The present invention contemplates an improved

bipolar electrode and methods for constructing same

and electrolytic cells containing the same. The bipolar

electrode includes an anodic member and a cathodic

member secured in a spaced apart relationship via at

least one fastener assembly. The anodic member and the

cathodic member are electrically connected for conducting

current therebetween, and the space between

the anodic member and the cathodic member is sealed

to substantially inhibit the flow of electrolyte into such

space during the operation of the hybrid bipolar electrode

in an electrolytic cell. In one form, the bipolar

electrode of the present invention includes a barrier

member interposed in the space between the anodic

member and the cathodic member and constructed of a

was consumed, the voltage drop across the electrolytic

cell was increased and the temperature of the electrolyte

increased with the result being the establishment of

an operating temperature range of approximately 25· C

5 to approximately 70· C. At the upper limit of this operating

temperature range, the loss of graphite as a result

of graphite oxidation was substantially increased and, in

some instances, cooling coils were included in the electrolytic

cell to cool the electrolyte in an attempt to

10 maintain the electrolyte temperature at a reduced level

(approximately 50· C, for example).

The erosion of the carbon bipolar electrodes caused

dimensional instability and resulted in a decreased current

efficiency as the carbon bipolar electrode was operated

over a period of time. Since the erosion of the

carbon bipolar electrodes was not uniform, current

density gradients were formed which caused further

deleterious effects on the operational characteristics of

the electrolytic cell.

20 In recent years, metal electrodes have been proposed

to be operated as anodes in bipolar electrolytic cells,

such bipolar electrodes also including a cathodic surface.

For example, anodic surfaces of titanium have

been proposed with cathodic surfaces bonded thereto

and such bipolar electrodes have been proposed for use

in chloride brines. A non-conductive film tends to form

on exposed titanium anodic surfaces in chloride brines;

however, this non-conductive film does not tend to

develop on precious metals, such as platinum, for example,

and platinum in combination with iridium or rubidium

coated titanium anodic surfaces have been utilized

in chlor-alkali electrolytic cell applications.

In the past, metal bipolar electrodes have been constructed

of titanium sheets bonded to steel plates, the

titanium sheets forming the anodic member and the

steel plate forming the cathodic member. One problem

encountered with such bi-metal bipolar electrodes was

that the titanium sheet was deformed via the action of

molecular hydrogen migrating through the cathodic

member to the anodic member forming an expanded

hydride with the titanium. This action resulted in a

weakening of the structural integrity of the bond between

the titanium sheet and the steel plate and, in many

instances, resulted in a separation of the titanium-steel

along the bonded surface.

Typical patents disclosing prior art devices of the

type generally referred to above are the U.S. Pat. Nos.

3,759,813, issued to Raetzsch, et ali 3,732,157, issued to

Dewitt; 3,043,757, issued to Holmes; 3,441,495, issued to

Colman; and 3,222,270, issued to Edwards.

4,085,027

BACKGROUND OF THE INVENTION

HYBRID BIPOLAR ELECTRODE

CROSS-REFERENCE TO RELATED

APPLICATIONS

Related subject matter is disclosed in the patent application,

Ser. No. 545,015, entitled "A BIPOLAR

ELECTRODE AND METHOD FOR CONSTRUCTING

SAME," filed on an even date with the

present application and assigned to the assignee of the

present invention.

1. Field of the Invention

The present invention relates generally to an im- 15

proved bipolar electrode and, more particularly, but not

by way of limitation, to an improved hybrid bipolar

electrode having an anodic member and a cathodic

member connected in a spaced apart relationship.

2. Brief Description of the Prior Art

In the past, many electrolytic cells have been proposed

for use in a variety of applications. Various electrodes

for use in electrolytic cell applications have also

been proposed in the past.

A typical prior art electrolytic cell included an anode 25

electrode and a cathode electrode immersed in an electrolyte

and an electrical power source connected to the

anode electrode and the cathode electrode, the positive

side of the power source being connected to the anode

electrode and the negative side of the power source 30

being connected to the cathode electrode. In this type

of electrolytic cell, the electrode functioning as the

anode and the electrode functioning as the cathode

were generally referred to in the art as "monopolar"

electrodes, i.e. each electrode functions as either an 35

anode or a cathode during electrolysis.

Another type of electrolytic cell included an anode

electrode and a cathode electrode and at least one electrode

interposed between the anode and the cathode

electrodes, each of the electrodes interposed between 40

the anode and the cathode electrodes having an anodic

member and a cathodic member and being referred to in

the art as "bipolar" electrodes. The cathodic member

and the anodic member of each bipolar electrode were

mechanically connected, and the cathodic member of 45

each of the bipolar electrodes was electrically in series

with the anodic members prior and subsequent thereto,

i.e. the current flowed through the electrolyte to the

cathodic member of the bipolar electrode, through the

bipolar electrode and from the anodic member of the 50

bipolar electrode through the electrolyte to the next

cathodic member of another bipolar electrode or to the

cathodic member of the monopolar cathode electrode

depending on the number of bipolar electrodes in the

electrolytic cell. 55

In the past, electrodes constructed of a carbon material

have been used in the construction ofboth monopolar

electrodes and bipolar electrodes. In some instances,

the anoclic surfaces were constructed of a carbon material

and the cathodic surfaces were constructed of a 60

ferrous material, this type of construction tending to

minimize contamination ofthe electrolyte which results

from the electrolytic erosion of many non-carbon anodes.

Bipolar electrodes have been constructed of graphite 65

and, in these instances, the graphite was continuously

consumed during electrolysis as a result of oxidation of

the graphite surfaces. As the graphite bipolar electrode

4,085,027

anodic member 12 is constructed of a titanium metal

sheet having a coating of a noble metal or oxide thereof

on the first face 20, such as platinum-iridium, platinum,

rubidium, ruthenium, osmium and oxides thereof and

the like, for example, the coating being electrically

conductive and forming the anodic surface on the anodic

member 12 (the coating forming the anodic surface

not being separately illustrated in the.drawings).

The cathodic member 14 is generally rectangularly

10 shaped and has a first face 34, a second face 36, a first

side 38, a second side 40, a third side 42 and fourth side

44. The cathodic member 14 is constructed such that

the first face 34 of the cathodic member 14 operates as

a cathodic surface in an electrolytic cell. In one preferred

embodiment, the hybrid bipolar electrode 10 is

utilized in an alkali metal chlorate or chlorine electrolyte

cell for the electrolysis of aqueous. solutions of

alkali metal chlorides in a manner mentioned before

with respect to the anodic member 12 and, in this one

preferred embodiment, the cathodic member 14 is constructed

of a carbon steel, stainless steel, or other ferrous

materials or non-ferrous materials such as copper,

nickel or molybdenum, for example, serviceable in chlorate

solutions.

A plurality of generally cylindrically· shaped depressions

46 are formed in the first face 34 of the cathodic

member 14. Each of the depressions 46 has an internal

diameter 48, as shown in FIG. 3, and forms an open

space SO extending a distance 52 generally into the first

30 face 34 of the cathodic member 14 terminating with an

end wall 56 (only some of the depressions 46 are specifically

designated in the drawings via a reference numeral

for clarity). Each of the depressions 46 forms a corresponding

raised portion on the second face 36 of the

cathodic member and each raised portion extends a

distance generally from the second face 36 terminating

with an end 54.

A plurality of openings 58 are formed through the

cathodic member 14, each opening 58 extending

through the cathodic.member 14 intersecting the first

face 34 and the second face 36 thereof. More particularly,

each of the openings 58 is formed through a central

portion of one of the depressions 46, each opening

58 intersecting the end wall 56 and the end 54 formed

via one of the depressions 46. The depressions 46 and,

more particularly, the openings 58 are spaced in accordance

.with a predetermined spacing pattern ·substantially

corresponding with the spacing pattern of the

openings 32 in the anodic member 12 and, in an assembled

position of the bipolar electrode . 10, each of the

openings 58· in the cathodic member 14 is substantially

aligned with one of the openings 32 in the anodic member

12.

The barrier member 18 is generally rectangularly

shaped and has a first face 60, a second face 62, a first

side 64, a second side 66, a third side 68 and a fourth side

70. A plurality of openings 72 are formed through the

barrier member 18 and each opening 72 extends through

the barrier member 18 intersecting the first face 60 and

the second face 62 thereof (only one of the openings 72

being shown in the drawings). The openings 72 are

spaced in accordance with a predetermined spacing

pattern corresponding with the spacing pattern of the

openings 32 in the anodic member 12 and corresponding

with the spacing pattern of the openings 58 in the

cathodic member 14. In an assembled position of the

bipolar electrode 10, each of the openings 72 in the

barrier member 18 is substantially aligned with one of

BRIEF DESCRIPTION OF THE DRAWINGS

material inhibiting the contact of hydrogen with the

anodic member in an electrolysis application.

FIG. 1· is an elevational view of the first face of an 5

anodic member of a hybrid bipolar electrode constructed

in accordance with the present invention.

FIG. 2 is an elevational view of the first face of a

cathodic member of the hybrid bipolar electrode.of the

present invention.

FIG. 3 is a fragmentary, partial sectional, partial

elevational view showing a typical first or second side

elevational view of the anodic member of FIG. 1 connected

via a fastener assembly to the cathodic member

of FIG. 2 forming the hybrid bipolar electrode of the 15

present invention, only two typical fastener assemblies

being shown in FIG. 3.

FIG. 4 is a fragmentary elevational view similar to

FIG. 3, but showing a typical third or fourth side elevational

view of the hybrid bipolar electrode of the pres- 20

ent invention, only two of the fastener assemblies being

shown in FIG. 4.

FIG. 5 is a fragmentary partial sectional, partial elevational

view showing the hybrid bipolar electrode of

the present invention in an electrolytic cell. 25

FIG. 6 is a fragmentary view similar to FIG. 3, but

showing a typical first or second side elevational view

of a modified hybrid bipolar electrode.

DESCRIPTION OF THE PREFERRED

EMBODIMENTS

Referring to the drawings and to FIGS. 1 through 4

in particular, shown therein and designated via the general

reference numeral 10 is a hybrid bipolar electrode

constructed in accordance with the present invention. 35

In general, the hybrid bipolar electrode includes an

anodic member 12, a cathodic member 14, a plurality of

fastener assemblies 16 connecting the anodic member 12

and the cathodic member 14 in a spaced apart relationship

(only some of the fastener assemblies being specifi- 40

cally shown in FIGS. 3 and 4, for clarity), and a barrier

member 18 disposed in the space between the anodic

member 12 and the cathodic member 14, the fastener

assemblies 16 also securing the barrier member 18 in an

assembled position supported between the anodic mem- 45

ber 12 and the cathodic member 14.

The anodic member 12 is generally rectangularly

shaped and has a first face 20, a second face 22, a first

side 24, a second side 26, a third side 28 and a fourth side

30.•A plurality of openings 32 are formed through the 50

anodic member 12 and each opening 32 extends through

the anodic member 12 intersecting the first face 20 and

the second face 22 thereof (only some of the openings

32 are specifically designated via a reference numeral in

the drawings for clarity). More particularly, each of the 55

openings 32 is sized and shaped to accommodate a portion

of one of the fastener assemblies 16, and, in one

preferred form, the openings 32 are spaced on the anodic

member 12 in accordance with a predetermined

spacing pattern arranged for cooperation with the fas- 60

tener assemblies 16 in a manner to be described below.

The anodic member 12 is constructed such that the

first face 20 of the anodic member 12. operates as an

anodic surface in an electrolytic cell. In one preferred

embodiment, the hybrid bipolar electrode 10 is utilized 65

in an alkali metal chlorate or chlorine electrolytic cell

for .the electrolysis of aqueous solutions of alkali metal

chlorides and, in this one preferred embodiment,. the

4,085,027

5 6

the openings 32 in the anodic member 12, each of the cathodic member 14 generally facing the second face 62

openings 72 in the barrier member 18 also being substan- of the barrier member 18. The cathodic member 14 is

tially aligned with one of the openings 58 in the ca- positioned such that the rod portions 78 of each of the

thodic member 14. bolt members 74 extends through one of the openings 58

Eachfastener assembly 16 includes a bolt member 72 5 in the cathodic member 14 and end face 88 of each of

having a head portion 76 and a threaded rod portion 78, the second spacers 84 generally faces the second face 36

only one of the fastener assemblies 16 being shown in of the cathodic member 14, a portion of each rod por-

FIGS. 3 and 4 for clarity. In a fastened position of the tion 78 extending a distance beyond the end wall 56

fastener assemblies 16, the rod member 78 of each bolt formed by one of the depressions 46 and being disposed

member 74 extends through one ofthe aligned openings 10 generally within one ofthe open spaces 50 formed in the

32 of the anodic member 12, through one of the aligned cathodic member 14 via the depressions 46. One of the

openings 72 of the barrier member 18, and through one nut members 80 is threadedly secured to the end portion

of the aligned openings 58 of the cathode member 14. of each rod portion 78 extending into the open space 50

Each of the fastener assemblies 16 also includes a nut formed via the depressions 46 and each of the nut memmember

80 having a threaded opening (not shown) 15 bers 80 is rotated in one direction threadedly engaging

extending a distance therethrough and sized to thread· one of the rod portions 78 and securing the hybrid bipoedly

engage the threaded rod portion 78 of one of the lar electrode 10 in an assembled position wherein the

bolt members 74, each nut member 80 being generally anodic member 12, the cathodic member 14 and the

disposed in one of the open spaces 50 formed in the barrier member 18 are disposed in generally parallel

depressions 46, in a fastened position of the fastener 20 extending planes in a spaced apart relationship, the ends

assemblies 16. 86 of each of the first spacers 82 are disposed generally

In one preferred embodiment, as shown in FIGS. 3 adjacent the second face 22 of the anodic member 12,

and 4, each fastener assembly 16 includes a first and a the ends 88 of each of the first spacers 82 are disposed

second spacer 82 and 84, respectively. The spacers 82 generally adjacent the first face 60 of the barrier memand

84 are similarly constructed and each spacer 82 and 25 ber 18, the ends 86 of each of the second spacers 84 are

84 has opposite end faces 86 and 88 and an opening 90 disposed generally adjacent the second face 62 of the

extending through a central portion thereof intersecting barrier member 18, and the ends 88 of each of the secthe

end faces 86 and 88. The first spacer 82 of each ond spacers 84 are disposed generally adjacent the secfastener

assembly 16 is disposed between the anodic ond face 36 ofthe cathodic member 14. Further, each of

member 12 and the barrier member 18 and the rod por- 30 the head portions 76 engages a portion of the first face

tion 78 of each of the bolt members 74 extends through 20 of the anodic member 12, each ofthe nut members 81)

the opening 80 formed through one of the first spacers engages a portion of the first face 34 of the cathodic

82, the bolt members 74 supporting the first spacers 82 member 14 and the rod portion ofeach ofthe bolt memin

an assembled position between the anodic member 12 bers 74 extends through the aligned openings 32, 58 and

and the barrier member 18. The second spacer 84 of 35 72 and through the openings 90 in the spacers 82 and 84.

each fastener assembly 16 is disposed between the ca- Thus, the fastener assemblies 16 mechanically connect

thodic member 14 and the barrier member 18 and the the anodic member 12, the cathodic member 14 and the

rod portion 78 of each of the bolt members 74 extends barrier member 18 in an assembled position with the

through the opening 90 formed through one of the second face 22 of the anodic member 12 spaced a dissecond

spacers 84, the bolt members 74 supporting the 40 tance 92 from the second face 36 of the cathodic memsecond

spacers 84 in an assembled position between the ber 14, and the first spacers 82 ofthe fastener assemblies

cathodic member 14 and the barrier member 18. 16 cooperate to secure the anodic member 12 in a

To assemble the hybrid bipolar electrode 10, the rod spaced apart relationship with respect to the barrier

portions 78 of the bolt members 74 are inserted through member 18 wherein the second face 22 of the anodic

the openings 32 in the anodic member 14 and each of 45 member 12 is spaced a distance 94 from the first face 60

the first spacers 82 are disposed on the rod portion 78 of of the barrier member 18, the second spacers 84 of the

one of the bolt members 74 with the rod portion 78 fastener assemblies 16 cooperating to secure the ca·

extending through the opening 90 in the first spacer 82, thodic member 14 in a spaced apart relationship with

the end face 86 of each of the first spacers 82 generally respect to the barrier member 18 wherein the second

facing the second face 22 of the anodic member 12. The 50 face 36 of the cathodic member 14 is spaced a distance

barrier member 18 is disposed near the anodic member 96 from the second face 62 of the barrier member 18. In

12 and positioned such that each of the openings 58 in a preferred form, each nut member 80 is sized and

the barrier member 18 is aligned with one of the open- shaped to be disposed in one of the open spaces 50

ings 32 in the anodic member 12, the first face 60 of the formed in the cathodic member 14 via the depressions

barrier member 18 generally facing the second face 22 55 46 and positioned therein such that the ends of each nut

of the anodic member 12. The barrier member 18 is member 80, opposite the ends engaging the end walls

positioned such that the rod portions 78 of each of the 56, are each disposed in a plane disposed generally

bolt members 74 extends through one ofthe openings 72 below and spaced a distance from the planar disposition

in the barrier member 18 and each of the second spacers of the first face 34 of the cathodic member 14. In one

84 is disposed on the rod portion 78 of one of the bolt 60 preferred embodiment, the bolt member 74 and the nut

members 74 with the rod portion 78 extending through member 80 of each of the fastener assembies 16 is conthe

opening 90 in the second spacer 84, the end face 86 structed of a material capable of conducting electrical

of each of the second spacers 84 generally facing the current or,mother words, an electrical conductor type

second face 62 of the barrier member 18. The cathodic of material, and, in this one preferred embodiment, a

member 14 is disposed near the barrier member 18 and 65 portion of each of the fastener assemblies 16, more parpositioned

such that each of the openings 58 mthe ticularly, is constructed ofan electrical conductor matecathodic

member 14 is aligned with one of the openings rial such as brass or copper, or example. In this embodi-

72 in the barrier member 18, the second face 36 of the ment ofthe present invention, the fastener assemblies 16

4,085,027

establish electrical continuity between the anodic member

12 and the cathodic member 14 in addition to mechanically

connecting the anodic member 12 and the'

cathodic member 14 in the spaced apart relationship.

The spacing of the fastener assemblies 16 with respect 5

to the anodic member 12 and the cathodic member 14 is

established to provide a uniform current density on the

cathodic member 14 and the anodic member 12 during

the operation of the hybrid bipolar electrode 10 in additin

to the mechanical connecting function of the fas- 10

tener assemblies 16, the spacing pattern of the fastener

assemblies 16 being a repetitive type of pattern as indicated

in FIGS. 1 and2'11

As mentioned before, the hybrid bipolar electrodes of

the present invention are particularly useful in an alkali 15

metal chlorate or chlorine electrolytic cell for the electrolysis

.of aqueous solutions of alkali metal chlorides.

Diagrammatically and schematically shown in FIG. 5 is

an electrolytic cell 100 comprising: a cell box 102 hav- 0

ing opposite side walls 104 and 106, opposite end walls 2

108 and 110 and a base 112 defining a space 114 for

retaining the electrolyte; a monopolar anodic electrode

116 connected via conventional means to the positive

side of an electrical power source 118 (more particu- 25

larly, a direct-current power source); a monopolar cathodic

electrode 120 connected via conventional means

to the negative side of the electrical power source 118;

and a plurality of the hybrid bipolar electrodes 10 disposed

between the anodic electrode 116 and the ca- 30

thodic electrode 120 (only the first hybrid bipolar electrode

10 next to the monopolar anodic electrode 116

and the last hybrid bipolar electrode 10 next to the

monopolar cathodic electrode 120 being shown in FIG.

~ ~

In one form, the cell box 102 includes a plurality of

openings 122 formed through the base 112 for introducing

the electrolyte into the space 114 formed in the cell

box ·102. A plurality of channels are formed in the side

wall 104, only four channels being shown in FIG. 5 and 40

designated therein via the reference numerals 124, 126,

128 and 130, and a plurality of channels are formed in

the side wall 106, each of the channels formed in the

side wall 106 being aligned with one of the channels

124,126, 128 and 130 formed in the side wall 104 (only 45

four channels being shown in FIG. 5 and designated

therein via. the reference numerals 132, 134, 136 and

138).

The monopolar anodic electrode 116 has opposite

sides 140 and 142 and a surface 144 operating as an 50

anodic surface during the operation. of the electrolytic

cell 100. The aligned channels 124 and 132 are sized and

positioned to slidingly receive the anodic electrode 116,

and the anodic electrode 116 is supported within the

space 114 and extends between the side walls 104 and 55

106, the anodic electrode 116 being at least partially

immersed in the electrolyte during the operation of the

electrolytic cell 100.

The monopolar cathodic electrode 120 has opposite

sides 146 and 148 and a surface ISO operating as a ca- 60

thodic surface during the operation of the electrolytic

cell 100. The aligned channels130 and 138 are sizedand

positioned to slidingly receive the cathodic electrode

120, and the cathodic electrode UO is supported within

the space 114 and extends between the side walls 104 6S

and 106. the cathodic electrode 120 beinS at least partially

immersed in the electrolyte dUrinS the operation

of the electrolytic cell 100.

Assuming the electrolytic cell 100 included only the

monopolar electrodes 116 and 120, the electrical power

source 118 would be connected to tne DlOnopolar electrodes

116 and 120, and the current would flow from

the anodic surface 144, through the electrolyte in the

space 114, and to the cathodic surface ISO. The anodic

surface 144 and the cathodic· surface ISO are spaced a

distance apart and the electrolyte is disposed generally

between the anodicsurface 144 and the cathodic surface

ISO. Further, the anodic monopolar electrode 116 is not

mechanically connected to the cathodic electrode 120.

Assuming further that the electrolytic cell 100 included

a plurality of monopolar anodic electrodes and a plurality

of monopolar cathodic electrodes, the monopolar

anodic electrodes would be connected in parallel to the

electrical power source and the monopolar cathodic

electrodes would be connected in parallel to the electrical

power source. This type of arrangement just described

would constitute a typical prior art monopolar

electrode type of electrolytic cell configuration.

The present invention is directed to an electrolytic

cell which includes at least one bipolar electrode, in

contrast to the electrolytic cell which includes only

monopolar electrodes described above. Thus, the electrolytic

cell 100, shown in FIG. 5, includes the monopolar

anodic electrode 116, the monopolar cathodic electrode

120 and one or more of the hybrid bipolar electrodes

10 of the present invention supported within the

cell box 102 space 114,generally between the monopolar

electrodes 116 and 118, and at least partially immersed

in the electrolyte during the operation of the

electrolytic cell 100.

The hybrid bipolar electrode 10 includes a seal member

152 (as shown in FIG. 5) extending generally about

the sides 24, 26, 28 and 30 of the anodic member 12 and

generally about the sides 38, 40, 42 and 44 of the cathodic

member 14. A portion of the seal member 152

sealingly engages the cathodic member 14 and a portion

of the seal member 152 sealingly engages the anodic

member 12 forming a fluid seal· between the anodic

member 12 and the cathodic member 14 to substantially

seal the electrolyte from the space between the second

face 22 of the anodic member 12 and the second face 36

ofcathodic member 14. Thus, a substantial portion of

the space between the second faces 22 and· 36 of the

anodic and the cathodic members 12 and 14 (depending

generally on the size, type and position of the sealmember

152, for example) is sealingly isolated from the electrolyte

solution during the operation of the electrolytic

cell 100. In addition to the seal member 152, each of the

openings 32 in the anodic member 12 and. each of the

openings 58 in the cathodic member 14 are preferably

sealed in a manner forming a seal between the fastener

assemblies 16 and the portions of the anodic member 12

and the cathodic member 14 generally near the openings

32 and 58. In one form, the engagement between

each of the head portions 76 and the first face 20 of the

anodic member 12 forms a seal for substantially inhibiting

the flow.of electrolyte through. the openings 32 in

the anodic member 12 into the space between the anodic

and the cathodic members 12 and 14, and the engagement

between each of the nut members 80 and the

first face 34 (the end walls 56) of the cathodic member

14 forms a seal for substantially inhibiting the flow of

electrolyte through the openings 58 in the cathodic

member 14 into· the space between the anodic and the

cathodic members 12 and· 14. It should be noted that

additional sealing material may be added to augmentthe

4,085,027

9 ro

mechanical seal formed via the engagement between formed on the first face 20 of the last hybrid bipolar

portions of the fastener assemblies 16 and the cathodic electrode 10 through the electrolyte to the cathodic

and the anodic members 14 and 12 if required in a par- surface 156 formed on the monopolar cathodic electicular

application. trode 120. It should be noted that the current flow to,

The aligned channels 126 and 134 in the cell box 102 5 through and from the hybrid bipolar electrodes 10 interare

sized and positioned to slidingly receive one of the mediate or disposed between the first and the last hyhybrid

bipolar electrodes 10 of the present invention brid bipolar electrode 10 has not peen referred to in

(the hybrid bipolar electrode 10 sometimes referred to detail in the foregoing description.

herein in connection with FIG. 5 as the first hybrid In summary, the cathodic surface on the cathodic

bipolar electrode 10), and the aligned channels 128 and 10 member 14 is mechanically connected to the anodic

136 in the cell box 102 are sized and positioned to slid- surface on the anodic member 12 of each hybrid bipolar

ingly receive another hybrid bipolar electrode 10 con- electrode, and the cathodic surface and the anodic surstructed

in accordance with the present invention (the face of each hybrid bipolar electrode 10 are in electrical

hybrid bipolar electrode 10 sometimes referred to series. In addition, the anodic surface of each hybrid

herein in connection with FIG. 5 as the last hybrid 15 bipolar electrode 10 generally faces and is spaced a

bipolar electrode 10). Each of the hybrid bipolar elec- distance from a cathodic surface of either the monopotrodes

10 is supported within the space 114 and extends lar cathodic electrode or one of the other hybrid bipolar

between the side walls 104 and 106. The channels 124, electrodes 10, and the current flows from the anodic

126, 128, 130, 132, 134, 136 and 138, are positioned to surface ofeach hybrid bipolar electrode 10, through the

support the electrodes 10, 116 and 120 in a spaced apart 20 electrolyte, to the cathodic surface of either the monorelationship.

The hybrid bipolar electrodes 10 are each polar cathodic electrode or one of the other hybrid

oriented such that the anodic surface formed on the first electrodes 10. The cathodic surface ofeach hybrid bipoface

20 of the anodic member 12 generally faces and is lar electrode 10 generally faces and is spaced a distance

spaced a distance from the cathodic surface formed on from an anodic surface of either the monopolar anodic

either the monopolar cathodic electrode 120 or the next 25 electrodes or one of the other hybrid bipolar electrodes

hybrid bipolar electrode 10 and the cathodic surface 10 and the current flows from the cathodic surface to

formed on the first face 34 of the cathodic member 14 the anodic surface via the fastener assemblies of each

generally faces and is spaced a distance from the anodic hybrid bipolar electrode 10.

surface formed on either the monopolar anodic elec- During the operation of the electrolytic cell 100, the

trode 116 or the next hybrid bipolar electrode 10, the 30 electrolyte is introduced into the space 114 of the cell

cathodic member 14 and the anodic member 12 of each box 102 via the openings 122, and the electrolyte is

hybrid bipolar electrode 10 being mechanically con· removed from the space 114 of the cell box 102 by

nected and in electrical series. For example, in an assem- overflowing over the top (not shown) of the cell box

bled position of the electrolytic cell 100, the anodic 102 or, in some instances, by passing the electrolyte

surface 144 formed on the monopolar anodic electrode 35 through openings (not shown) in the cell box 102 gener-

116 is spaced a distance 154 from the cathodic surface ally near the top thereof. In some applications, the cell

formed on the first face 34 of the first hybrid bipolar box 102 is supported within a larger cell tank (not

electrode 10 in a direction generally from the monopo- shown) and the electrolyte is retained within the cell

lar anodic electrode 116 toward the monopolar ca- tank circulated into the cell box 102 from the cell tank,

thodic electrode 120; the anodic surface formed on the 40 removed from the cell box 102 and circulated back into

first face 20 of the first hybrid bipolar electrode 10 is the cell tank, a cooling coil being disposed in the cell

spaced a distance from the cathodic surface formed on tank in contact with the electrolyte for maintaining the

the first face 34 of the next hybrid bipolar electrode 10 electrolyte at a predetermined temperature level during

(not shown in FIG. 5) in a direction generally from the the electrolysis operation. The construction and operamonopolar

anodic electrode 116 toward the monopolar 45 tion of cell boxes and cell tanks and the use of cell boxes

cathodic electrode 120jand the anodic surface formed in electrolytic applications is well known in the art, and

on the fIrst face 20 of the last hybrid bipolar electrode a further detailed description is not required herein.

10 in the electrolytic cell 100 is spaced a distance 156 As mentioned before, the hybrid bipolar electrode 10

from the cathodic surface 150 formed on the monopolar is particularly suitable for service in an alkali metal

cathodic electrode 120. During the operation of the 50 chlorate or chlorine electrolytic cell for the electrolysis

electrolytic cell 100 of the present invention the current of aqueous solutions of alkali metal chlorides, and, in

flows from the anodic surface 144 of the monopolar this one preferred embodiment the anodic member 12 is

anodic electrode 116 through the electrolyte to the constructed of a metal comprising or consisting essencathodic

surface formed on the first face 34 of the first tially of titanium and an anodic surface is formed on the

hybrid bipolar electrode 10; the current flows through 55 first face 20 ofthe anodic member 12 by coating the frrst

the first hybrid bipolar electrode 10 from the cathodic face 20 with a precious metal or oxide thereof. Further,

member 14 to the anodic member 12 via the fastener in this embodiment of the present invention, the caassemblies

16; the current flows from the anodic surface thodic member 14 is constructed of a metal comprising

formed on the first face 20 of the first hybrid bipolar or consisting essentially ofcarbon steel, stainless steel or

electrode 10 through the electrolyte to the cathodic 60 ferrous materials or non-ferrous materials serviceable in

surface formed on the frrst face 34 of the next hybrid chlorate solutions, the frrst face 34 of the cathodic memo

bipolar electrode 10 (not shown in FIG. 5); the current ber 14 operating as the cathodic surface of the hybrid

flows through the electrolyte to the cathodic surface bipolar electrode. In an alkali metal chlorate or chlorine

formed on the first face 34 of the last hybrid bipolar electrolytic cell application and utilizing an anodic

electrode 10; the current flows through the last hybrid 65 member 12 and a cathodic member 14 constructed as

bipolar electrode 10 from the cathodic member 14 to just described above, the barrier member 18 is conthe

anodic member 12 via the fastener assemblies 16; structed of a material operating to shield or provide a

and finally the current flows from the anodic surface hydrogen barrier for substantially inhibiting the migra4,085,027

tion of atomic hydrogen forming at the cathodic surface

provided via the first face 34 of the cathodic member 14

during the operation of the electrolytic cell, the migrationof

atomic hydrogen occurring through the ca·

thodic member 14 and tending to attack the titanium 5

anodic member,12 and the barrier member 18 substantially

preventing the atomic hydrogen from attacking

the anodic member 12 and forming titanium hydrides.

The formation of titanium hydrides on the' titanium

anodic member 12 caused warping and, in some applica- 10

tions, also caused disintegration of the anodic member

14, the formation of titanium hydrides also resulting in

titanium hydride embrittlement. It has been proposed to

clad the cathodic surface of a bipolar electrode constructed

of titanium with steel to prevent the formation 15

of titanium hydrides; however, it has been found that

the thickness of the steel necessary to prevent the hydrogen

from diffusing to the titanium was substantially

large and, in many applications, prohibitive as far as an

economically feasible or practical solution. In addition, 20

it was required that the cladding edges be sealed from

the anodic electrical potential, otherwise the steel

would be substantially dissolved in the electrolyte. The

hybrid electrode of the present invention provides a

bipolar electrode wherein the anOdic member can be 25

constructed •• of a metal comprising titanium and yet

substantially reducing the' possibility of titanium hy.

drides attacking the titanium anodic member 12.

In one preferred embodiment, the barrier member 18

is constructed of an inert material such as a polyvinyl 30

chloride (PVC or PVDC or CPVC or the like, for

example) type of material, for example. In this embodi·

ment, the barrier member 18 also operates to provide

the hydrogen barrier substantially insulating the anodic

member 12 from the cathodic member 14, except for the 35

fastener assemblies 16 which are constructed of an electrically

conductive material and establish electrical

continuity between the, anodic member .12 and the cathodic

member 14, in a preferred embodiment. In this

operational embodiment wherein the anodic member 12 40

is constructed of a metal consisting essentially of titanium,

the cathodic member 14 is constructed of a metal

providing a surface operating as a cathodic surface and

the barrier member 18 is constructed essentially of an

inert material; the bolt members 74 and the nut member 45

80 are each preferably constructed of an electrically

conductive material such as copper or brass or the like,

for example, the first spacer 82 is preferably constructed

of a metal consisting .essentially of titanium, and the

second spacer 84 is constructed of a metal comprising 50

carbon steel or a stainIess steel or other ferrous or nonferrous

materials or the like, for example.

It should also be noted that a plurality of depressions

could be formed in the anodic member 12 to accommodate

the head portions 76 of the bolt members 74 in a 55

manner similar to that described before with respect to

the depressions 46 in the cathodic member 14 and the

nut members 80.

In the embodiment of the invention shown in FIGS.

1 through 4, the first spacers 82 operate to space.the 60

second face 22 of the anodic member 12 a distance from

the first face 60 of the barrier member 18, and the second

spacers 84 operate to space the second face 36 of

the cathodic member 14 and the ends 54 portion of the

second face 36 of the cathodic member 14 a distance 65

from the second face 62 of the barrier member 18. The

first and second spacers 82 and 84 cooperate with the

barrier member 18 to space the second face 22 of the

anodic member 12 the distance 92 from the second face

36 of the cathodic member 14. Thus, the elements of the

hybrid bipolar electrode 10 which are constructed of a

metal comprising titanium are isolated and spaced from

the cathodic member 14 i.e. the hydrogen producing

member or elements as'in the case of the second spacer

84. The spacing of the elements constructed of a metal

comprising titanium from the hydrogen producing elements

(the cathodic member 14) and the disposition and

construction of the barrier member 14 cooperate to

substantially reduce the possibility of hydrogen attack·

ing the elements constructed of titanium and provide a

metal bipolar electrode having an anodic member constructed

of titanium which is serviceable in an alkali

metal chlorate or chlorine electrolytic cell application.

EMBODIMENT OF FIG. 6

Shown in FIG. 6 is a modified hybrid bipolar electrode

lOa which is constructed exactly like the hybrid

bipolar. electrode 10, except the hybrid bipolar electrode

lOa includes a modified barrier member 180 and

the fastener assemblies 160 do not include, spacers similar

to the spacers 82 and 84 of the hybrid bipolar electrode

10. Thus, the first face 60 of the barrier member

180 generally abuts the. second face 22 of the anodic

member 12 and the second face 62 of the barrier memo

ber 180 is disposed near and generally abuts the second

face 36 ofthe cathodic member 14, the second face 62 of

the barrier member 180, more particularly, abutting

ends 54 portions of the second face 36 of the cathodic

member 14 and the second face 62 of the barrier member

180 being spaced a distance 160 from. the second

face 36 of the cathodic member 14 via the raised portions

formed by the depressions 46 (not shown in FIG.

6) and the corresponding raised portions on the cathodic

member 14. It should be noted that, in this em·

bodiment of the invention, the second face 62 of the

barrier member 180 can abut the second face 36 of the

cathodic member 14 if the depressions 46 are eliminated.

In this embodiment of the invention, the barrier memo

ber 180 is constructed ofa material comprising graphite,

in one preferred form, and the barrier member 180,

more particularly, is constructed of an oil impregnated

type of graphite. The barrier member 180 operates to

provide a hydrogen barrier substantially inhibiting the

migration of atomic hydrogen to the anodic member 12

and the resulting formation of titanium hydrides in a

manner like that described before with respect to the

barrier member 18. However, in this embodiment of the

invention, the bamer member 180 is also constructed of

an electrically conductive material (graphite or oil impregnated

graphite, for example), and the barrier memo

~r 180 cooperates with the spacing pattern of the fastener

assemblies 16 to enhance the establishment of a

substantially uniform current density on the anodic

member 12 and the cathodic member 14:

The hybrid bipolar'electrode lOa provides a particularly

useful construction for converting the' bipolar

electrodes of existing electrolytic cells.to the type of

bipolar electrode construction of the present invention.

For example, some existing alkali metal chlorate or

chlorine electrolytic cells presently utilize bipolar electrodes

constructed essentially of graphite and each of

these existing graphite electrodes can be utilized to form

the barrier member 180. It should be noted that, in some

instances, it may be desirable to reduce the thickness of

the existing graphite electrodes to form the barrier

4,085,027

member 180. For example, some typical existing graphite

electrodes have a thickness of approximately I.1

inches and the thickness of the barrier member 18a of

the replacing hybrid bipolar electrode lOa would be

approximately ! inches, assuming the replacing hybrid 5

bipolar electrode lOa is intended to be utilized under

approximately equivalent operating conditions as the

replaced existing graphite electrodes.

The hybrid bipolar electrode lOa is assembled in a

manner similar to that described before with respect to 10

the hybrid bipolar electrode 10.except the assembly

steps do not include provisions for installing the spacers

82 and 84 since the necessity ofproviding the spacers 82

and 84 is eliminated via the construction of the hybrid

bipolar electrode lOa. The hybrid bipolar electrode lOa 15

is sealed via the seal member 152 in a manner like that

described before with respect to the seal member 152

and the hybrid bipolar electrode 10, and the hybrid

bipolar electrode lOa is installed and operates in an

electrolytic cell in a manner like that described before 20

with respect to the electrolytic cell 100 and the hybrid

bipolar electrodes 10. The hybrid bipolar electrode lOa

is shown in FIG. 5 assembled in the electrolytic cell

100; however, it should be noted that the barrier member

180 is shown in FIG. 5 spaced a slight distance from 25

the anodic member 12 and the cathodic member 14

merely for the purpose of diagrammatically illustrating

the various aspects of the present invention and it is not

required to space the barrier member 180 from the anodic

member 12 or the cathodic member 14 in this last 30

described embodiment of the invention.

Changes may be made in the construction and the

arrangement of the various parts or the elements of the

embodiments disclosed herein or in the steps of the

method disclosed herein without departing from the 35

spirit and the scope of the invention as defined in the

following claims.

What is claimed is:

1. A hybrid bipolar electrode, for use in an electrolytic

cell wherein the bipolar electrode is at least par- 40

tially immersed in an electrolyte, said bipolar electrode

comprising:

an anodic member having a first face and a second

face;

a cathodic member having a first face and a second 45

face;

means for supporting the anodic member and the

cathodic member in a spaced apart relationship

with the second face of the anodic member being

spaced a distance from the second face of the ca- 50

thodic member;

means engaging portions of the anodic member and

the cathodic member for substantially sealing electrolyte

from a substantial portion of the space between

the anodic and the cathodic members; and 55

means having a portion constructed of an electrically

conductive material and portions contacting the

anodic member and the cathodic member, said

means electrically connecting the anodic member

and the cathodic member in series. 60

2. The hybrid bipolar electrode of claim 1 defined

further to include:

a barrier member disposed in the space between the

anodic member and the cathodic member, the barrier

member shielding the anodic member from the 65

cathodic member.

3. The hybrid bipolar electrode of claim 2 defined

further to include:

at least one first spacer, each first spacer being disposed

between the anodic member and the barrier

member and spacingthe anodic member a distance

from the barrier member.

4. The hybrid bipolar electrode of claim 3 defined

further to include:

at least one second spacer, each second spacer being

disposed between the cathodic member and the

barrier member and spacing the cathodic member a

distance from the barrier member.

5. The hybrid bipolar electrode of claim 3 wherein

the anodic member is constructed ofa material comprising

titanium and the barrier member is constructed ofan

inert material, the barrier member inhibiting the migration

of hydrogen from the. cathodic member to the

anodic member.

6. The hybrid bipolar electrode of 2 wherein the

anodic member is constructed of a material comprising

titanium and the barrier member is constructed of a

material selected from a group consisting of graphite

and polyvinyl chloride.

7. The hybrid bipolar electrode of claim 6 wherein

the barrier member includes a first face and a second

face, the first. face. of the barrier member abutting a

portion ofthe second face ofthe anodic member and the

second face of the barrier member abutting a portion of

the second face of the cathodic member; and wherein

the means supporting the anodic member and the cathodic

member in a spaced apart relationship is defined

further as supporting the barrier member between the

second face of the anodic member and the second face

of the cathodic member, the second face of the anodic

member being spaced a distance from the second face of

the cathodic member.

8. The hybrid bipolar electrode of claim 2 wherein

the anodic member includes at least one opening, each

opening being formed through the anodic member intersecting

the first and the second faces of the anodic

member; and wherein the cathodic member includes at

least one opening, each opening being formed through

the cathodic member intersecting the first and the second

faces of the cathodic member, each opening in the

cathodic member being aligned with an opening in the

anodic member; and wherein the means supporting the

anodic member and the cathodic member in a spaced

apart relationship is defined further to include:

at least one fastener assembly, each fastener assembly

having a portion extending through one of the

openings in the anodic member and through one of

the openings in the cathodic member, and each

fastener assembly having a portion engaging the

anodic member and a portion engaging the cathodic

member, the fastener assemblies mechanically

connecting the anodic member and the cathodic

member in a spaced apart relationship.

9. The hybrid bipolar electrode of claim 8 wherein

the barrier member includes at least one opening, each

opening extending through the barrier member, and

each opening in the barrier member being aligned with

one of the openings in the anodic member and with one

of the openings in the cathodic member; and wherein

each fastener assembly is defmed further to include a

portion extending through one of the openings in the

barrier member, the fastener assemblies supporting the

barrier member in the space between the anodic member

and the cathodic member.

10. The hybrid bipolar electrode of claim 2 wherein

the means supporting the anodic member and the ca4,085,027

thodic member in a spaced apart relationship is defined

further to include:

at least one fastener assembly each fastener assembly

having a portion engaging the anodic member, a

portion engaging the barrier member and a portion S

engaging the cathodic member, the fastener assemblies

mechanically connecting the anodic member

and the cathodic member in the spaced apart relationship

and supporting the barrier member in the

space between the anodic member and the cathodic 10

member.

11. The bipolar electrode of claim 1 wherein the

means supporting the anodic member and the cathodic

member in a spaced apart relationship is defmed further

to include a plurality of fastener assemblies, each fas- IS

tener assembly having a portion connected to the anodic

member and a portion connected to the cathodic

member, each fastener assembly mechanically connecting

and establishing electrical continuity between the

anodic member and the cathodic member. 20

12. The hybrid bipolar electrode of claim 1 wherein

the anodic member is defined further to include a coating

on the fust face thereof operating as an anodic surface

in an electrolysis application, the second face ofthe

anodic member being spaced a distance from the second 2S

face of the cathodic member and the fust face of the

cathodic member operating as a cathodic surface in an

electrolysis application.

. 13. An improved electrolytic cell having electrodes

connected. to an electrical power source and at least 30

partially immersed in an electrolyte wherein the electrolyticcell

includes at least one bipolar electrode including.

an anodic member having. a •first face and a

second face and a cathodic member having a first face

and a second face, the improvement comprising:

at least one fastener assembly, each fastener assembly

haVing a portion connected to.the anodic member

and a portion connected to the cathodic member of

each bipolar electrode in the electrolytic cell, each

fastener assembly·.mechanically connecting the

anodic member and the cathodic member in a

spaced apart relationship with the second face of

the anodic member spaced a distance from the

second face of the cathodic member;

means engaging portions of the anodic member and

the cathodic member for substantially sealing electrolyte

from a· substantial portion ofthe space between

the anodic and the cathodic members; and

means having a portion constructed of an electrically

conductive material and portions contacting the

anodic member and the cathodic member, said

means electrically connecting the anodic member

and the cathodic member in series.

14. The electrolytic cell of claim 13 wherein the improvement

is defmed further to include:

a barrier member disposed in the space between the

anodic member and the cathodic member, the barrier

member shielding the anodic member from the

cathodic member. • • • • •

rR��lg0�(D�xt-autospace:none'>14

contacting said extract phase with at least the stoichiometric

quantity of an aqueous alkaline solution

required to neutralize the chloride form of said

amine to selectively separate said platinum values

from said palladium values in said organic extract

phase. and form a platinum stripped organic extract

phase and an aqueous platinum containing strip

solution, and

isolating said aqueous solution from said platinum

extract phase.

14. A continuous process for the separation and selective

recovery of palladium dissolved in aqueous chloride

solutions with platinum which comprises:

reducing said solution to an emf between about -425

mvand -650 mv,

contacting said aqueous chloride solution for a predetermined

time period with an organic solvent containing

at least 1% by weight of an organically

substituted secondary amine compound of the general

formula:

wherein R1 and Rz are hydrocarbon groups and R1 +

Rzcontain between 18 and 35 carbon atoms, said compound

capable of forming complexes of platinum and

palladium that are preferentially soluble in the organic

xolvent and whereby said contacting results in the creation

of an organic extract phase and an aqueous raffinate

phase, •

separating said organic extract phase from said aqueous

raffinate phase,

contacting said organic extract phase with an aqueous

solution containing a reducing agent acidified to

between about 0.1 to about 3.0 N-HCl to strip

palladium values from said organic extract phase,

said contact resulting in the formation of a palladium

loaded aqueous phase and a stripped organic

phase containing said platinum,

separating said loaded aqeuous phase and said

stripped organic phase, and recovering palladium

from said loaded aqueous phase.

* * * * *

no<ĩet0�(D�e:none'>point of elemental sulfur.

* * * * *

ture between about 500 C and the melting point of

sulfur to convert substantially all of the sulfide

sulfur to elemental sulfur in solid form and to effect

conversion of the metal compounds to metal chlorides,

and recovering metal from the chlorides.

22. The process of claim 21 in which chlorination is

performed at a temperature between about 800 C and

the melting point of sulfur.

23. The process of claim 2] in which the minerals

10 contain silver.

24. The process of claim 23 in which the silver containing

mineral is tetrahedrite.

25. The process of claim 21 in which sulfur chlorides

formed during dry chlorination are reacted with the

15 metal sulfides to form metal chlorides and elemental

sulfur.

26. The process of claim 25 in which the process is

performed by introducing the metal sulfides and dry

chlorine gas countercurrently into the reaction zone

20 and an inert sweep gas is introduced into the reaction

zone to bring sulfur chlorides formed during the dry

chlorination into contact with metal sulfides entering

the reaction zone.

4,011,146

lead, silver recovered from the leach solution by cementation,

the leach solution after removal of lead and

silver therefrom recycled to the sodium chloride leaching

step, the improvement comprising preventing the

build-up of zinc in the leach solution in the leaching 5

step by removing a bleed stream from the lead and

silver depleted leach solution, removing zinc from the

bleed stream and recycling the bleed stream to the

leaching solution in the leaching step.

19. The process of claim 18 including subjecting the

bleed stream to electrolysis after removal of zinc therefrom

to produce chlorine gas and recycling the chlorine

gas to the dry chlorination step.

20. The process of claim 19 in which the zinc is removed

by precipitating it as zinc carbonate by the addition

of sodium carbonate, the sodium hydroxide produced

in the electrolyis is carbonated to sodium carbonate

and the sodium carbonate recycled to the zinc

precipitation step.

21. The process of recovering metal values from

minerals of the polymorphic series of complex metal

sulfides tetrahedrite-tennantite comprising:

a. subjecting the minerals to dry chlorination with

chlorine gas in the absence of oxygen at a tempera-