Note: Descriptions are shown in the official language in which they were submitted.
1~2~t~6
C-7174 This invention relates to electrodes for electroly-
tic cells.
Numerous solutions have been proposed for the
problem of interelectrode contact during interleaving
of planar electrodes for diaphragm type electrolytic
cells, among such solutions being expandable or
contractable electrodes which can be reduced in thic~-
ness during the interleaving operation to increase
the anode-to-cathode gap during interleaving and
thereby lessen abrasive contact between electrodes
and yet still be able to expand to assume a normal
thickness with a lesser desired anode-to-cathode
gap following interleaving so as to allow efficient
cell operation.
However, all of such methods and apparatus for
:~ expandable electrodes involve use of an electrode
having either a "riser", or vertical conductor bar,
or a horizontal electrode supportive conductor bar.
This is so because there is a dual need first to support
the electrode working faces and second to conduct
electricity to or from the working faces during
electrolysis. However, the presence of this riser
has limited the contraction of the electrode and
limited flexibility of the electrode in the direction
parallel said conductor bar or riser. In the prior
art designs this is a problem because the elecirodes
are not precisely aligned prior to installation unless
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,
rather detailed and cumbersome adjustments and measurements
are made. ~lso, the expansion and contraction is generally
designed to be uniform along the direction of the conductor
bar, whereas the most desirable configuration during inter-
leaving would seem to be a minimum thickness at the end
which will be inserted between opposed electrodes.
Also, there is a need for an electrode which can automatically
adapt to various configurations of opposed electrodes with-
out extensive modification, so that slightly irregular
opposed electrodes can be used, if desired. Therefore,
there is need for a better, more flexible electrode.
; A solution to these and other problems is the
apparatus which is the subject of our copending Canadian
Patent Application No. 301,154, filed April 14, 1978, of which
this application is a divisional, and which provides an
expandable electrode assembly, which comprises:
a) at least two opposed planar working faces
of flexible electrically conductive material,
said faces defining a riserless open chamber
therebetween; ~-
b) at least one spring means, interposed between .-
said working faces, for biasing said faces
a limited distance away from each other and
for allowing inward movement of said faces in
an inward direction toward each other in response.
to a force .applied to said working faces in
said inward direction; and
c) an electrical connector means, affixed to one
edge of each of said planar faces,..for elëctrically
connecting said faces to a sUpportive backplate
without limiting said inward movement of the
edge of said faces opposite said one edge.
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~z~
The present invention is particularly concerned
with a combination of an expandable electrode of the type
having two opposed working surfaces with an outwardly
biasing spring means therebetween, and the improvement
which comprises:
a) first stiffener bar means, attached to
one of said two working faces and having
an outward projection, for spreading
inward and outward forces along said
one of said working faces so as to produce
more uniform movements of said one of said
working faces; -
b) second stiffener bar means, attached to the
other of said two working faces and having
an outward projection, for spreading inward
and outward forces along said other of said
working faces so as to produce more uniform
movements of said other of said working faces;
c) keeper plate means, surrounding said outward
projections, for automatically limiting
movement of said projections away from each
other and allowing unrestrained movement of
said projections toward one another.
The objects and advantages of the invention will
be better understood bv reference to the attached drawing
in which:
FIGURE 1 is a side elevational view of an electrode
embodying the invention of copending Canadian Patent Application
No. 301,154;
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FIGURE 2 iS a top plan view of the electrode of
FIGURE l;
FIGURE 3 iS a top plan view of a right end portion
of the electrode of FIGURE 2;
FIGURE 4 iS a top plan view of a left end portion
of the electrode of FIGURE 3;
FIGURE 5 iS an isometric view of a second electrode
embodying the invention presently claimed;
FIGURB 6 is a cross-sectional view through an
electrolytic cell showing the electrode of FIGURE 5
in contracted position; :
FIGURE 7 is a cross-sectional view through an :
electrolytic cell showing the electrode of FIGURE 5
in expanded position;
FIGURE 8 iS a vertical cross-sectional view taken
along lines 8-8 of FIGURE 7, showing a keeper assembly;
FIGURE 9 iS a horizontal cross-section taken
along lines 9-9 of FIGURE 8, showing a stiffener bar;
FIGURE 10 iS an isometric view of the keeper
plate of FIGURE 8, and
FIGURE 11 which appears on the first drawing sheet,
is a vertical cross-section similar to that of FIGURE 8,
but showing instead a preferred leaf spring and hook
assembly which could be substituted for the keeper assembly
of FIGURE 8.
As used herein "diaphragm" shall include membranes
of the ion exchange type as well as fabric-like synthetic
diaphragm structures and materials and also include the
more conventional vacuum formed separative layers customarily
provided in electrolytic cells, such as for example those used
75~6
to produce alkali metal hydroxides and halogens from alkali
metal halide solutions.
FIGURE 1 is a side elevational view of a first
preferred embodiment of the electrode which is covered by
copending Canadian Patent Application No. 301,154 aforesaid,
although this embodiment does not incorporate the keeper
plate of the present invention the description is included
herein for completeness.
Electrode 10 is a planar electrode of any suitable
10 electrolytic cell having planar interleaved electrodes, such
as for example the electrolytic diaphragm cell of U.S. Patent
No. 3,~9~,149 issued August 5, 1975 to rl. S. Kircher and
E. N. ~lacken, which discloses tuhular bodied diaphragm type
electrolytic cells having multiple interleaved planar electrodes.
Electrode 10 could alternatively be an electrode usable in a
conventional diaphragm cell such as that disclosed in U.S.
Patent No. 3,904,504 issued September 9, 1975 to W. W. Ruthel
and L. G. Evans or some other similar cell. -
11275~
C-7174 Referrina now to FIGURES 1-4, electrode 10
comprîses two working faces 12 and 13, a conauctor
bar 30 and a plurality of stiffener bars 22-29.
Working faces 12 and 13 are rectangular planar
foraminous ~esh sheets having top edges 14 and 15,
bottom edges 16 and 17 (not shownl, outer edges 18
and 19 and inner edges 20 and 21,
respectively. Faces 12 and 13 can be separate and
unconnected as shown in the Figures, in some embodi-
ments, or surfaces 12 and 13 may be joined across
the "front", "leadino" or "outer" edges 18 and 19,
for example, by attaching a flexible section of the
same mesh material employed as surfaces 12 and 13.
The flexible section may also be attached by means
such as soldering, welding, brazing or the like. If
desired, the electrode surfaces can also be joined
along the other edges. This is re~uired where, for
example, the electrode surfaces serve as a cathode in
a diaphragm cell which has a vacuum deposited asbestos fiber
type diaphraçm. The electroae surfaces could be sealed
; along the edges and the electrode surfaces also attached I
to the electrode plate to form a liquid impervious
catholyte chamber. A diaphragm could then be attached
or deposited on the electrode surfaces of the electrode
and outlets could be provided for the removal of
gaseous and liquid products from the electrode compart-
ment. In the case of a cathode where any of the
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.. . .
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edges 14, 15, 16, 17, 18, 19, 20 or 21 are not connected
it is preferred to have the mesh either doubled hack
against itself (see FIGURE 3) or capped to protect the
diaphragm from scratching, puncturing or tearing due to
; sharp exposed edges being forced against the diaphragm.
It will be understood that, depending on whether
the electrode assembly of the present invention serves as a
cathode or anode, the materials of construction for the
faces 12 and 13 are suitably selected to be resistant to
the gases and liquids to which faces 12 and 13 are exposed.
For example, while the electrode is serving as an anode,
faces 12 and 13 can be a conductive metal having a platinum
group metal electrocatalytic coating. As used herein
"platinum group metal" means an element of the group consisting
of ruthenium, palladium, rhodium, osmium, iridium and platinum.
Where the electrode assembly serves as the cathode, the mesh
is suitably, for example, stainless steel, carbon steel, ~ -~
; nickel, copper, iron or a coated conductive material such
as nickel-molybdenum coated copper.
When the electrode is used as an anode, surfaces 12
and 13 can be in various forms such as flexible solid sheets,
flexible perforated sheets or flexible expanded mesh which
is flattened or unflattened and can have slits horizontally,
vertically or angularly. Other suitable forms include ~ -
flexible woven wire which is flattened or unflattened, bars
or wires, or strips arranged, for example, vertically and
sheets having perforations, slits or louvered openings.
.
i :
75~
C-7174 A preferred anode working face is a foraminous
metal mesh having good electrical conductivity in the
d-~rection perpendicular to conductor bar 30 along the
face. Preferred materials for such an anode are either
titanium or silicon com~ounds.
In the case of a cathode, faces 12 and 13 are suitably a
metal screen or mesh where the metal is, for example,
stainless steel, iron, carbon steel, nickel or tantalum.
Conductor bars 30 can be of any convenient form
such as rods, strips or bars. A preferxed conductor
bar 30 is a bar of copper. In one preferred configur-
ation, conductor bar 30 is attached to inner edges 20,
21 of faces 12,13 respectively. The conauctor bar 30
conducts current to or from faces 12,13 depending on
the polarity of the electrode 10.
As best seen in FIGURES 2-4, a plurality of parallel
stiffener bars 22, 23, 24 and 25 are connected to face
13 by welds or rivets 32 and preferably lie parallel
to and spaced from conductor bar 30, although the
particular orientation of bars 22, 23, 24 and 25 could
be changed so as to achieve flexibility in any ~esired
direction. Corresponding stiffener bars 26, 27, 28
and 29 are connected to face 12-and lie in parallel
opposed contact with bars 22-25, respectively. Bars
22-29 are comprised of a resilient material so that
they ser~e as a spring ~etween faces 12 and 13 tending
to force faces 12 and 13 a limited d;stance away from
7~6
C-7174 one another and yet ca~able of allo~ing movement of
faces 12 and 13 toward each ot~er.
FIGURE 3 shows preferred stiffener bars 22 and 26
in greater detail. Stiffener bar 22 is seen to comprise
a middle portion 22c and two side portions 22a and 22b
projecting arcuately from face 13 toward face 12 and
outwardly from middle portion 22c. Stiffener bar 26
has corresponding middle portion 26c and side portions
26a and 26b. Middle portions 22c and 26c are cGnnected
by suitable welds or rivets 32 to faces 13 and 12,
respectively. Side portionS22a and 26a abut resiliently,
as do side portions 22c and 26c. Abutting stiffener
bars 22 and 26 thus serve to resiliently bias faces 12
and 13 a limited distance apart. If desired, portions
22a and 26a can be connected by welding as can portions
22c and 26c. The remaining stiffenér bars 23-25 and
27-29 can be constructed and àbutted in similar manner
to provide four combination bars (not nu~bered). Any
other number of stiffener bars could be used, if desired.
The stiffener bars, preferably keinc parallel conductor
bar 30, serve to give the electrode rigidity in the
direction parallel to conductor bar 30. In FIGURES
~ 1-4, this direction is vertical, although it will be
- appreciated that the conductor bar 30 could be oriented
horizontally, as for example ~y placing the conductor
bar along top edges 14 and 15 instead of inner edges
20,21 and then orienting a suitable number of stiffener
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75~6
bars in the horizontal direction or even inclined slightly
to serve as baffles for gas. Stiffener bars 22-29 also
serve to give the electrode some rigidity. However any
rigidi-ty in the "longitudinal" direction or direction of
current flow, i.e., from inner edges 20,21 toward outer edges
18,19 is only indirectly provided by the rigidity in the other
two directions above noted. Thus the electrode 10 is able
to contract and yield when interleaved between two opposed
electrodes.
The inner edges 20,21 can be connected to conductor
bar 30 as shown in FIGURE 4, or in any other suitable manner.
In FIGURE 4, welds 34 are provided to connect flattened mesh
portions 38 and 36 of faces 12 and 13, respectively to con-
ductor bar 30 and the flattening of portions 36 and 38 in
turn provides shoulders 40 and 41 facing toward conductor bar
30 and resisting movement of conductor bar 30 and faces 12 and
13 further toward one another.
A second electrode 11 is shown in FIGURES 5-10.
20 Electrode 11 comprises conductor bar 30, faces 12 and 13 and
a plurality of stiffener bars 42-49. Stiffener bars 42-49
correspond in position to previously described bars 22-29,
however bars 42-49 need not be resilient and are preferably
made of very rigid material. Bars 47-49 are positioned opposite
: bars 43-45 in the same manner as bar 46 is opposite bar 42.
Like bars 22-29, bars 42-49 can be conductive, if desired,
but run transverse to the direction of electrical flow and
hence are not properly termed "conductors".
Also, while stiffener bars 22-29 abutted one
another, stiffener bars 42-49 do not abut, but rather are
spaced apart a limited distance sufficient to allow for
"contraction" or motion of face 12 toward face 13, as
during the interleaving operation. Stiffener bars 42-45 are
connected by welds 50 to face 13 and stiffener bars 46-49 are
connected to face 12 by corresponding welds 50. In accordance
with this invention, faces 12 and 13 can be interconnected
by a keeper plate assembly 67 (see FIGURES 8-10) which limits
outward movement of faces 12 and 13 away from each other.
A spring 52 (see FIGURE 6) is provided to resiliently bias
stiffener bars 42-45 away from corresponding stiffener bars
46-49 and thereby resiliently bias face 13 away from face 12.
Referring to FIGURES 6 and 7, faces 12 and 13
can be provided with edge protectors 62 to protect against
damage to any diaphragm or membrane 56 which otherwise might
occur due to sharp exposed edges of faces 12 and 13. FIGURES
6 and 7 are cross-sectional views through an electrolytic cell
such as that of U.S. Patent No. 3,898,149 to M. S. Kircher
et al issued August 5, 1975. In FIGURE 6 faces 12 and 13 of
electrode 11 are surrounded by a membrane 56. Membrane 56
can also be a "diaphragm" of either the synthetic fabric
type or could be a vacuum deposited "fibrous" diaphragm
1~275~
such as asi)~stos, synt}letic re~in or mixtures thereof
if edges 14-21 were joined by flexib]Le mesh or other
suitable means for fully supporting the diaphragm.
In FIGURES 5, 6 and 7, electrode 11 is a cathoae and
interleaved between anodes 57 and 57a. Anodes 57 and 57a
comprise first faces 58 and 58a, second faces 59 and 59a
and conductor bars 60 and 60a. Anodes 57 and 57a are rigid
electrodes, which could abrade, bind or tear diaphragm or
membrane 56 if electrode llwere not capable of contraction
during the interleaving procedure. Conductors 60,60a of anodes
57,57a are typical of prior art configurations which result in
longitudinal rigiaity. However, expandable or contractable
anodes could also be constructed in accordance with the invention
and substituted for rigid anodes 57 and 57a.
A suitable method of contracting electrodes 10 ana 11
is use of a vacuum assembly method such as that disclosed in
U.S. Patent No. 4,078,987 which issued March 14, 1978 by
J. S. Specht. In such a method the flexible electrode 10 or
11 is enclosed by a gas flo~7 resistant diaphragm or membrane.
: 20 Fluid conduits are provided to the interior-of the diaphragm
enclosed flexible electrode and through these conduits the
electrode is evacuated at least
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75~6
partially to create a differential pressure upon said
diaphragm which in turn presses against the electrode and
contracts the electrode. This pressure differential is
maintained during interleaving of anodes and cathodes so
as to achieve a greater anode to cathode gap durin~ such
interleaving and thereby help prevent damage to the diaphragm.
Also, other suitable contraction means can be used, including
simply forcing the electrode 11 between anodes 57,57a and
allowing the resilient electrode 11 to contract under the
force of insertion. Slip sheets could be placed over the
outer edges 18 and 19 and surrounding diaphragm to protect
the diaphragm during the initial stages of such insertion.
FIGURES 6 and 7 show electrode 11 in contracted
and expanded position, respectively. Inward movement of
faces 12 and 13 and hence minimum thickness are limited by
engagement of inner edges 96 and 98 (see FIGURE 8) of
stiffener bars 42-45 with stiffener bars 46-49 and outward
expansion by keeper assemblies 67.
FIGURES 8-10 show keeper assembly 67 in greater
detail. Keeper assembly 67 comprises top flanges 68 and
70 of stiffener bar 42 and 46, respectively, nuts 72 and
; 74, keeper bolts 80 and 82 and keeper plate 84. Top flanges
68 and 70 are preferably a horizontally inwardly bent integral
part of stiffener bars 42 and 46, respectively. Flanges 68
and 70 define vertical boltholes 76 and 78 (see FIGURE 9)
aligned with threaded holes of nuts 72 and 74 so as to receive
and secure keeper bolts 80 and 82 in a vertical orientation.
Keeper plate 84 (see FIGURE 10) has a central slot 86 and
first and second stop portions 88 and 90 to limit movement
of keeper bolts 80 and 82 outwardly away from one another.
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Keeper bolts 80 and 82 are inserted through slot 86 and
boltholes 76 and 78 and threaded into engagement with nuts
72 and 74. Keeper bolts 80 and 82 have boltheads 92 and 94
to prevent keeper plate 84 from moving upwardly off of keeper
bolts 80 and 82. A similar keeper assembly 67 and spring
52 are at the lower end of stiffener bars 42 and 46 and at
the upper and lower ends of stiffener bar pairs 43 and 47,
44 and 48, and 45 and 49 thus limiting the outward relative
movement of faces 12 and 13 and limited spring-biased inward
relative movement of faces 12 and 13 therehy limiting
"expansion" of electrode 11. "Contraction" of electrode 11
is limited by engagement of inner rims 96 of stiffener bars
42-45 with inner rims 98 of stiffener bars 46-49. Springs 52
or lugs (not shown) or electrode ends 62 could similarly
serve to limit contraction. Inwardly projecting ledges 53
and 55 are preferably provided on stiffener bars 42-45 and
! 46-49, respectively to maintain the vertical positions of the
spring 52 adjacent each such assembly 67. Springs 52 could
be replaced by leaf springs of suitable design, and such leaf
springs could be supported bv hooks engaging ledges 6~ and 70.
These leaf springs and hooks could substitute for keeper
assembly 67.
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7~6
C~7174 A preferred leaf spring and hook assembly 100 is seen
in FIGURE 11. Assembly laa includes a J-leaf spring 102,
L-ends 104 and rivets 106. Springs 102 are leaf springs
adapted to fit within modified versiGns of stiffener bars
42a~4qa Conly 42a and 46a are shown~. Springs 102 have an
outer end 108, a central portion 110 and an inner end 112.
Springs 102 are riveted at outer end 108 to bars 42a-49a.
Ends 112 lie in sliding contact with stiffener bars 42a-
45a. Thus when mesh 12a and 13a (see below) are moved
toward one another in response to an applied external
force, portions 110 tend to flatten out and ends 112 slide
do~n~ard awav from rivets 106. Spring 102 is made of
resilient material which opposes 'his flattening and which
rebounds to expand the electrode when the external force
is lessened. Outer end 108 is a J-shaped hook which opens
toward the interior of the electrode. Also, upper sides
14a and 15a are provided and are flattened portions of
mesh 12a and 13a. This flattenting tends to give extra
; rigidity to the edges of the mesh without significantly
decreasing flexibility. It will be understood that there
are preferably eight such assemblies 100, one at each of
the lower and upper ends of the four pairs of stiffener
bars. The assembly 100 at the lower end of the stiffener
bar ~ould preferably be inverted from that of FIGURE 11
in order that end 112 thereof move upwardly toward the
interior of the electrode rather than do~n~ardly.
The operation of electrodes 10 and 11 is self-
evident from the above description. It should be noted
that conductor bar 30 will maintain a fixed thickness
of electrodes 10 and 11 at inner edges 20 and 21, so
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1~'~$~
that the electrodes lO and ll will assume a somewhat tapered
configuration in at least the region between bars 25,29 or
45,49 and conductor bar 30 since the bars are
resiliently interconnected to make electrodes lO and ll
contractable and expandable.
It will be appreciated that the particular member
of bars is a matter of design choice dependent on the size
and flexibility of the material utilized for faces 12 and 13.
The diaphragm or membrane 56 can be of any suitable
material such as an inert membrane composed of an inert,
flexible material having cation exchange properties and
which is impervious to the hydrodynamic flow of the electrolyte
and the passage of chlorine gas and chloride ions. A first
preferred membrane material is a perfluorosulfonic acid resin
membrane composed of a copolymer of a polyfluoroolefin with a
sulfonated perfluorovinyl ether. The equivalent weight of
the perfluorosulfonic acid resin is from about 900 to about
1600, and preferably from about llO0 to about 1500. The
perfluorosulfonic acid resin may be supported by a polyfluoro-
olefin fabric. A composite membrane sold commercially by
E. I. DuPont deNemours and Company under the trademark "Nafion"
is a suitable example of the preferred membrane.
A second preferred membrane is a cation exchange
membrane using a carboxyl group as the ion exchange group
and having an ion exchange capacity of 0.5-2.0 mEq/g
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75~
C-7174 of dry resin. Such a membrane can be produced by
chemically substituting a carboxyl group for the
sulfonic group in the above-descri~ed "Nafion" membrane
to produce a perfluorocarboxylic acid resin supported
by a polyfluoroolefin fa~ric. A second method of
producing the above-described cation exchange membrane
having a carboxyl group as its ion exchange group is
that described in Japanese Patent Publication No.
1976-126398 by Asahi Glass Kabushiki Kaisha issued
November 4, 1976. This method includes direct
copolymerization of fluorinated olefin monomers and
- monomers containing a carboxyl group or other poly-
merizable groups which can be converted to carboxyl
groups.
Alternatively, membrane 56 can be a aiaphragm of
conventional vacùum deposited asbestos fiber or other
suitable fibers or can be a polymer stabilized asbestos
or other fiber diaphragm or a synthetic fabric-like
structure comprised of particles of the perfluorosulfoniC
acid resin or perfluorocarboxylic acid resin above
disclosed or other suitable separative material.
The electrodes 10 and 11 may also be used in cells
havins no diaphragm, such cells being conventionally
designea to produce oxychlorine compounds or alkali
metal chlorates.
7S~G
C-7174 An anode backplate 61 is seen supporting anodes 57 and 57a of FIGURES 6 and 7. A corresponding conductive or non-
conductive backplate could be provided to define, in part,
the electrolytic cell and to support conductor bar 30.
Conductor ~ar 30 cculd be bolted to the corresponding back-
plate. ~owever, conductor ~ar 30 must be electrically
; connected to either anodic or cathodic bus bars, depending
on whether electrode 10 or 11 is an anode or cathode,
respectively, although such connection can be indirect.
With the above detailed description in mind as a
preferred example, it will be appreciated that many ~.odifi-
cations are possible. For example, the conductor bar 30
could be eliminated and the faces connected directly to an
electrode backplate or conductive cell wall, in which case
the backplate or wall would serve as the conductor bar 30.
Also, an~ mesh design could be used so long as the mesh
provides sufficient ccnductivity and flexibility. Also,
any sprlng desian other than the compression spring design
shGwn for Cpring 52 can be utilize~ so long as the spring
desisn will allow expansion and contraction of the electrode
in the above-described manner, for example, a leaf spring
havinc hoo}.ed ends passing through corresponding apertures
in the stiffener bar top flanges 68 and 70. Such a leaf
spring could also serve as the keeper assembly. ~hile the
electrode is described in terms of utility in a cell
which processes concentrated brine to produce caustic
soda, chlorine and hydrogen, cells using other raw
materials to make other products can also utili~e the
invention and the invention includes such usages. The
mesh of faces 12 and 13 mav be louvered such as, for
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example, in U.S. Patent No. 3,930,151 to Shibata et al issued
December 30, 1975, so long as sufficient space is provided
for electrode contraction. The invention can be used as
cathodes and anodes in the same cell with or without diaphragms
or membranes over the electrode of this invention. A spacer
mesh can be utilized between the electrode and membrane or
diaphragm to achieve a desired final gap between one or both
of the anodes and cathodes and the diaphragm or membrane.
The following claims are thus to be accorded the broad range
of equivalents which the invention encompasses.
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