Improvements in Electrolytic Decompositions, and especially in the Electrolytic Production of Bleaching Agents and their Uses, and in Electrodes and Apparatus therefor.
Year: 1895

page_text: Date of Application, 4th June, 1895
Complete Specification Left, 3rd Mar., 1856--Accepted, 4th Apr., 1896
PROVISIONAL SPECIFICATION.
Improvements in Electrolytic Decompositions, and especially in the
Electrolytic Production of Bleaching Agents and their Uses, and
in Electrodes and Apparatus therefor.
I, HENRY BLACKMAN, of No. 132 Mulberry Street, in the City of New York,
State of New York, in the United States of America, Manufacturer, do hereby
declare the nature of this invention to be as follows:-—
This invention relates generally to electrolytic processes for the decomposition
of liquids, and particularly solutions, such as aqueous solutions, of chlorides such
as sodium chloride, for the production of bleaching substances and alkalis.
The invention provides improved apparatus therefor, and particularly improved
electrodes or anodes for use in such electrolytic decompositions.
The invention also relates especially to bleaching by means of an electrolytically
prepared bleaching agent, useful particularly for the whitening of paper pulp, etc.,
although applicable generally for the bleaching of fibres, textile fabrics, etc.
I will first describe my invention as applied to electric bleaching.
When an aqueous solution of a chloride, for example sodium chloride, is
subjected to electrolysis, it is decomposed, the sodium liberated at the cathode in
turn decomposing the water, combining with one equivalent of hydrogen and the
oxygen to form sodium hydroxide, the other equivalent of hydrogen being set free
and escaping in bubbles, while the chlorine which appears at the anode will
(unless in some way prevented from so doing) combine with the sodium hydroxide,
which undergoes a new reaction and produces sodium hypochlorite, NaClO.
This hypochlorite constitutes a valuable bleaching agent. The same essential
reaction will occur by the use of a chloride or other alkalis or alkaline earths, as
for example if magnesium chloride be thus electrolyzed there results magnesium
hypochlorite.
Heretofore efforts have been made to practise bleaching by generating these
hypochlorites electrolytically, but their instability, in connection with the difficulty
of making other than a very weak bleaching solution, has rendered these efforts
only partly successful. It has been found that if the electrolysis be continued
sufficiently to produce other than a weak solution of (for example) sodium
hypochlorite, this hypochlorite by reason of its great. instability degenerates into
sodium chloride and sodium chlorate, both of which are devoid of bleaching
properties. On the other hand, such a weak solution of a bypochlorite as can be
produced by electrolysis, is found to bleach so slowly that the process affords little
or no economic advantages over the ordinary method of bleaching.
My improved mode of bleaching is based upon a discovery which I have made,
namely, that by heating such a weak solution of a hypochlorite to a sufficient
temperature, its activity as a bleaching agent is greatly intensified, and the
bleaching operation sufficiently expedited to render its use profitable. I electrolyze
an aqueous solution of sodium (or other) chloride, and after drawing off the
electrolyte, I heat it to the required temperature, and perform the bleaching while
maintaining it heated. The temperature should be that which gives the maximum
activity of bleaching with the minimum loss of sodium hypochlorite by degenera-
tion. I have found a temperature of from 130 degrees to 160 degrees Fahrenheit
to give the best results. To utilize the spent bleaching liquor, which still contains

page_text: over ninety per cent. of the original brine, it is desirable to return it to the
electrolytic cell and further electrolyze it, thereby rendering the process continuous;
but to return the liquid while hot would decrease the efficiency of the electrolytic
action, thereby causing waste of energy. I therefore first cool the spent liquor to
a sufficiently low temperature before passing it back to the electrolytic cell to be
re-electrolyzed.
Fig. 1 of the accompanying drawings is a sectional elevation of the apparatus
preferably employed in this process of bleaching;
Fig. 2 is a plau view thereof;
Fig. 3 is a vertical section of the electrolyzer on a larger scale;
Fig. 4 is a fragmentary plan thereof.
Referring to the drawings, let A designate an electrolytic cell or electrolyzer,
B a suitable heater, C a bleaching tank of any suitable kind, D a circulating
pump, E a cooler, and H a percolator for refortifying the brine.
The electrolyzer A. may be of any suitable construction. In the construction
shown it has an enclosing box or tank a, with a perforated pipe b for admitting
the electrolyte, a perforated pipe c for removing the electrolyte, and alternate
electrodes or plates, the anodes being lettered d d and connected to a conducting
*nd d¹ at one side, and the cathodes being lettered ee and connected to a conducting
rod at the other side. The liquid circulating from the pipe to c has to flow in
thin streams between the respective plates, and is thereby subjected to the
electrolytic action of electric currents Howing from the anode plates toward the
adjacent cathode plates. The outlet pipe c is extended upward at c¹ to maintain
the liquid at a level sufficient to keep the plates submerged.
b
A pipe conducts the electrolyte or bleaching liquid thence to the heater B,
and bleaching tank C, the flow being controlled by a valve f¹, and entering by a
nozzle 1.
The heater B may be variously constructed, the particular construction shown
consisting of a coil of the pipe within a chamber or casing into which steam
enters through a pipe g, being controlled by a valve g¹. The water of condensation
is discharged by a trap g.
Another construction of heater B is shown in Fig. 5, where the heater consists
simply of the steam pipe g extended within the pipe which conducts the bleaching
liquid. The steam is condensed and mingles with the liquid, giving up its heat
thereto.
In lieu of or in addition to the heater B, the liquid may be heated in the tank C
by means of the heater B₁ shown best in Fig. 2, consisting of a coil of pipe in the
tank through which steam is circulated, controlled by a valve g², the water of
condensation being removed by a strap 93. Thus the bleaching liquid may be
heated either before it enters the bleaching tank or after.
The particular construction of bleaching tank C shown is designed especially
for treating paper pulp, being known as a beater engine. As usual, it has a
cylinder C formed with knives or paddles working against fixed knives C¹
beneath, and throwing the pulp up over a dam C³. The operation is the same as
that of any beater engine. The bleaching and pulp mixing and grinding operations
may be conducted simultaneously. For removing the excess of bleaching liquid
from the tank as fast as new liquid enters, the tank is provided with the usual
revolving washer or strainer F, consisting of a wire gauze cylinder through the
meshes of which the liquid can flow but not the fibrous matter, and having
internal dippers which scoop up the entering liquid and direct it out through the
discharge pipe F', from which it falls into the hopper F2 and descends into the
tank G. From this tank the brine is pumped by the pump D through a pipe h,
which lifts it and discharges it into the percolator H. This percolator is filled
with a bed of salt, through which the brine flows, so that it dissolves the salt and
is thereby strengthened. From the percolator the refortified brine descends by a
pipe and passes through the cooler E. This cooler may be of any suitable
construction, that shown consisting simply of a tank through which the brine flows

page_text: in contact with a coil of cold pipes i, these pipes carrying a stream of cold fluid
such as ice water, or preferably being cooled by a liquid which is refrigerated by
an ice machine. By this or any suitable means, the entering brine is cooled, and
passes out from the cooler through a pipe h2 back to the electrolyzer A, which it
enters again by the perforated pipe b, and is re-electrolyzed and again used for
bleaching.
Thus the bleaching operation in the tank C proceeds continuously and rapidly
at the specified temperature, the strength of the bleaching liquid being continually
fortified by drawing off a quantity of it by means of the strainer F and supplying
its place with the fresh liquid which enters from the electrolyzer. When the
entire quantity of pulp has been sufficiently bleached it is run out into a drainer
where the bleaching liquor is strained out of it, this liquor being then pumped
back to the tank G. The pulp is finally washed in a percolator to expel the
remaining quantity of bleaching liquid, and may be dried by a centrifugal machine.
In practising my process, the brine should have a density of over two degrees
Beaumé, and preferably four to six degrees, and the electrolyzer may convert
from five to ten per cent. of the brine into sodium hypochlorite. The electric
energy required will depend upon circumstances, but I have successfully employed
a pressure of from 4 to 5 volts. The continual circulation of the brine to maintain
a continuous process is not essential to my invention, as the brine may first be
electrolyzed and then run into a tank and heated, and left in contact with the
matter to be bleached for the necessary time without any circulation.
In such electrolytic processes as the foregoing, it is found that a heating action
occurs in the electrolytic cell, and that as soon as a considerable degree of heat
is manifested the electrolytic action becomes less effective, the electric energy
being apparently wasted in part in the production of heat, instead of being fully
utilized in the chemical decomposition. The object of one part of my invention is
to prevent or counteract such heating of the cell, in order to prevent waste of
To this end my
electric energy and facilitate the chemical decomposition.
invention provides for the artificial cooling of the electrolyte in the cell by
continually drawing it off from the cell and passing it through a cooler in the
manner already described, and returning the cooled electrolyte to the cell, at the
same time maintaining it cool while in the cell by the application of cooling pipes
or surfaces within the cell.
In the apparatus already described, I have illustrated a coil of cooling pipes jj
applied in the upper part of the cell or electrolyzer A, to which the warmest
portion of the electrolyte rises, in order to cool this electrolyte. Through these
pipes any cold fluid may be passed such as ice-water, or cold brine. Preferably
the cold brine circuit of a refrigerating machine is applied in connection with the
apparatus in the manner shown in Figs. 1 and 2. In these figures the pipes k k
constitute a cold brine circuit. The brine is cooled in a chill tank J, which is
kept cool by the coils of an ammonia refrigerating machine, or any other known
refrigerating apparatus. From this tank the chilled brine is pumped off by a
pump K and circulated through the circuit of pipes k, passing first through the
cooling coil in the electrolyzer A, whereby the brine takes up some heat from
the electrolyte, after which it is passed through the cooling coils i of the cooler E,
whereby the brine takes up the heat from the warm electrolyte and cools it down
to the proper temperature for entering the electrolyzer. The brine thus warmed
is then returned to the chill tank J to be again cooled.
Fig. 6 is a side elevation mostly in vertical section illustrating the application
of my invention to an apparatus for electrolyzing sodium chloride for the
production of free chloride and caustic soda.
Fig. 7 is a sectional plan of the electrolytic cell thereof.
The apparatus shown in these figures illustrates a useful application of this
feature of my invention. The electrolytic cell lettered A is of different
construction from that first described, having a porous partition or septum m
dividing it into two chambers, in one of which is placed the anode d, and in the

page_text: other of which is placed the cathode e. The anode chamber is enclosed by a
tight fitting hood or cover n, to which is connected an outlet pipe n¹ for conducting
away the chlorine gas. The cathode chamber is open at top for the free escape
of the hydrogen gas, and is extended downward for the accumulation of the
caustic soda, NaHO, which is conducted off by a siphon or goose-neck p, and
carried away by a pipe pl. The brine to be electrolyzed is prepared or
strengthened in the percolator H as before described, and descends thence by a
pipe to the cooler E, wherein it is cooled by contact with the cold pipes i, and
then descends by a pipe h² to the anode chamber of the electrolyzer. An excess
of brine is introduced, so that a portion of it continually passes out by an overflow
opening r, and descends by the pipe f to the tank G, from which it is pumped up
by the pump D through the pipe h, which conducts it back to the percolator H.
In the upper part of the electrolyzer A', is arranged a cooling coil of pipe j,
which is connected in a brine circuit k k as before described. The cold brine
circuit includes a chill tank J for cooling the brine, and the brine is circulated
by a pump K, the cold brine flowing first through the coil in the
electrolyzer, and then through the coil in the cooler E, and then back to the
chill tank.
For supplying the cathode chamber with brine to take the place of that which
is decomposed, a valved pipe L may be provided leading from a separate reservoir
of brine, so that the brine thus introduced is free from chlorine.
By this process the electrolyte is maintained in constant circulation, that which
is contained in the electrolytic cell undergoing a slow movement from the inlet to
the outlet pipes, and while it remains in the cell being exposed to the cooling
action of the coil by which any heating action of the electrolytic cell is counter-
acted. The electrolysis liberates chlorine at the anode, which is confined by the
bell n and passes out by the pipe n¹; caustic soda is generated in contact with
the cathode e, and by its greater specific gravity it falls to the bottom of the cell
and passes out by the pipe p. The electrolyte is first cooled in the cooler E
before entering the cell A, in which latter it is again cooled or maintained cool by
the cooler or coil j. The cooler ; need not be a coil of pipe, but any other
suitable construction will answer. The cooler E may be any known construction
of cooler or attemperator, being preferably one in which the cooling medium and
the electrolyte being cooled are caused to flow past each other in opposite
directions.
Fig. 8 shows the application of my present invention to the construction of a
centrifugal electrolytic cell such as that described in the Specification of my
Patent No. 19,170, dated October 25, 1892. For a description of the special
construction and operation of this cell, reference is made to that Patent. So far
as my present invention is concerned, it is only necessary to say that the
centrifugal cell is provided with a coil of pipe M, so arranged as to be just outside
of the cylindrical surface assumed by the liquid under centrifugal force, in order
consequently to be immersed in the liquid of lowest specific gravity. This coil is
connected at one end by a pipe q to a trough or channel q', while at its other end
it terminates in a discharge pipe s, the liquid discharged from this pipe being
caught by a stationary channel or gutter t. The coil M may be made a part of the
cold brine circuit k k shown in Fig. 6, the brine or other cold liquid being introduced
by a pipe k to the trough g', wherein it is held by centrifugal force, and by the
same force is caused to flow through the coil M, being finally discharged by the
pipes and caught by the gutter t, from which it flows off by the pipe. Thus
the cold liquid is circulated through the coil M, and serves to cool the electrolyte
in the centrifugal cell while the latter is revolving.
The extent to which the electrolyte should be cooled according to my invention
cannot be stated with exactness, it being necessarily only sufficient to overcome
and counteract the heating tendency of the cell, the amount of cooling
consequently varying with the volume of current and the energy of the electro-
lytic action. The electrolyte may thus be maintained at any temperature at or

page_text: below the normal, the lower the temperature the more effective being the result,
except that the temperature should not be too close to the freezing point of the
electrolyte.
My invention also provides improved electrodes or anodes for use in electrolytic
decompositions, such as electrolysis of sodium chloride either in aqueous solution
as already described or rendered liquid by fusion. In the electrolysis of chlorine
salts and some other substances, much difficulty has been experienced because of
the rapid destruction of the electrodes, particularly the anode, during the
electrolytic action. According to my invention I use as the material for the
anode an electro-conductive metallic oxide which is substantially resistant to such
products of electrolysis of chlorine compounds as are liberated at the anode, that is,
the electro-negative products. The best examples of such metallic oxides that
I have found are magnetic iron oxide or "magnetite," Fe3O4, and iron-titanium
oxide or "ilmenite" (FeTi)2O3. These oxides are almost wholly unacted upon
during the electrolysis of an aqueous solution of sodium chloride. They have the
advantage of being good conductors, and when used as the anode do not speck
or discolor the electrolyte, and have great durability against corrosion or
disintegration; in fact I have found that the longer they are used the less they
are affected.
The iron or analogous oxides (as magnetite or ilmenite) may be used in the
form in which they occur as minerals, by sawing or otherwise shaping the mineral
into a slab, cylinder or other desired shape. Or it is within my invention to cast.
the oxide into the desired shape for the electrode by adding to it a sufficient
proportion of suitable fluxing agents, such as silica, lime and magnesia, to enable
it to be fused and caused to flow, but such fluxes being non-conductors, should not
be in such large proportion as to materially impair the electric conductivity of
the electrode. I have successfully used a composition known as "black slag"
from pig iron furnaces, which consists chiefly of a magnetic iron oxide or oxides,.
with a small proportion of various fluxing ingredients, enabling it to be fused and
cast.
"
My improved anode can be used in the electrolysis of aqueous solutions, or of
molten or fused electrolytes. In the latter case, the electrolyte may be fused by
heat externally applied, or if it offers sufficient resistance to the passage of the
electric current through it, the heat thus generated may serve to keep it fused.
My new electrode may be used in the electrolysis of other substances than chlorine
compounds, being especially advantageous in any case where the electrolytic.
process develops a powerful oxidizing action at the anode.
Dated this 4th day of June 1895
J. C. MEWBURN & ELLIS,
55 and 56 Chancery Lane, London, Chartered Patent Agents.
COMPLETE SPECIFICATION.
Improvements in Electrolytic Decompositions, and especially in the
Electrolytic Production of Bleaching Agents and their Uses, and
in Electrodes and Apparatus therefor.
1, HENRY BLACKMAN, of No. 132 Mulberry Street, in the City of New York,
State of New York, in the United States of America, Manufacturer, do hereby
declare the nature of the said invention and in what manner the same is to be
performed, to be particularly described and ascertained in and by the following
statement :-
This invention relates generally to electrolytic processes for the decomposition
of liquids, and particularly solutions, such as aqueous solutions, of chlorides such.

page_text: as sodium chloride, for the production of bleaching substances and alkalis. The
invention provides improved apparatus therefor, and particularly improved
electrodes or anodes for use in such electrolytic decompositions.
The invention also relates especially to bleaching by means of an electrolytically
prepared bleaching agent, useful particularly. for the whitening of paper
pulp, etc., although applicable generally for the bleaching of fibres, textile
fabrics, etc.
I will first describe my invention as applied to electric bleaching.
When an aqueous solution of a chloride, for example sodium chloride, is
subjected to electrolysis, is decomposed, the sodium liberated at the cathode in
turn decomposing the water, combining with one equivalent of hydrogen and the
oxygen to form sodium hydroxide, the other equivalent of hydrogen being set free
and escaping in bubbles, while the chlorine which appears at the anode will (unless
in some way prevented from so doing) combine with the sodium hydroxide, which
undergoes a new reaction and produces sodium hypochlorite, NaCIO. This
hypochlorite constitutes a valuable bleaching agent. The same essential reaction
will occur by the use of a chloride of other alkalis or alkaline earths, as for
example if magnesium chloride be thus electrolyzed there results magnesiu:n
hypochlorite.
Heretofore efforts have been made to practise bleaching by generating these
bypochlorites electrolytically, but their instability, in connection with the difficulty
of making other than a very weak bleaching solution, has rendered these efforts
only partly successful. It has been found that if the electrolysis be continued
sufficiently to produce other than a weak solution of (for example) sodium hypo-
chlorite, this hypochlorite by reason of its great instability degenerates into
sodium chloride and sodium chlorate, both of which are devoid of bleaching
properties. On the other hand, such a weak solution of a hypochlorite
as can be produced by electrolysis, is found to bleach so slowly that the
process affords little or no economic advantages over the ordinary method of
bleaching.
*
My improved mode of bleaching is based upon a discovery which I have made,
namely, that by heating such a weak solution of a hypochlorite to a sufficient
temperature, its activity as a bleaching agent is greatly intensified, and the
bleaching operation sufficiently expedited to render its use profitable. I electro-
lyze an aqueous solution of sodium (or other) chloride, and after drawing off the
electrolyte, I heat it to the required temperature and perform the bleaching while
maintaining it heated. The temperature should be that which gives the maximum
activity of bleaching with the minimum proportionate loss of sodium hypochlorite
by degeneration. When heated to the boiling point this hypochlorite degenerates
somewhat rapidly to chloride and chlorate, for which reason the temperature should
not be raised so high as to approach too closely to the boiling point. I have found
a temperature of from 130 degrees to 160 degrees Fahrenheit to give the best
results. Between these limits the bleaching effect is several times more rapid than
at the normal temperature, and the loss by conversion is not rapid enough to affect
the commercial effectiveness of the bleaching process. To utilize the spent bleaching
liquor, which still contains over ninety per cent. of the original brine, it is desirable
to return it to the electrolytic cell and further electrolyze it, thereby rendering the
process continuous; but to return the liquid while hot would decrease the efficiency
of the electrolytic action, thereby causing waste of energy. I therefore first cool
the spent liquor to a sufficiently low temperature before passing it back to the
electrolytic cell to be re-electrolyzed.
Fig. 1 of the drawings left with my Provisional Specification is a sectional elevation
of the apparatus preferably employed in this process of bleaching;
Fig. 2 is a plan view thereof;
Fig. 3 is a vertical section of the electrolyzer on a larger scale;
Fig. 4 is a fragmentary plan thereof.
Referring to the said drawings, let A designate an electrolytic cell or

page_text: electrolyzer, 1 a suitable heater, a bleaching tank of any suitable kind,
Da circulating pump, E a cooler, and H a percolator for refortifying the
brine.
C
The electrolyzer A may be of any suitable construction. In the construction
shown it has an enclosing box or tank a, with a perforated pipe o for admitting the
electrolyte, a perforated pipe c for removing the electrolyte, and alternate electrodes
or plates, the anodes being lettered d d and connected to a conducting rod d¹ at one
side, and the cathodes being lettered e e and connected to a conducting rod e¹ at
the other side. The liquid circulating from the pipe b to chas to flow in thin streams
between the respective plates, and is thereby subjected to the electrolytic action of
electric currents flowing from the anode plates toward the adjacent cathode plates.
The outlet pipe c is extended upward at e¹ to maintain the liquid at a level sufficient
to keep the plates submerged.
A pipe conducts the electrolyte or bleaching liquid thence to the heater B,
and bleaching tank C, the flow being controlled by a valve f', and entering by a
nozzle l.
The heater B may be variously constructed, the particular construction shown
consisting of a coil of the pipe f within a chamber or casing into which steam enters
through a pipe g, being controlled by a valve g¹. The water of condensation is
discharged by a trap g¹.
Another construction of heater B is shown in Fig. 5, where the heater consists
simply of the steam pipe g extended within the pipe which conducts the bleaching
liquid. The steam is condensed and mingles with the liquid, giving up its heat
thereto.
In lieu of or in addition to the heater B, the liquid may be heated in the tank C
by means of a beater B' shown best in Fig. 2, consisting of a coil of pipe in the
tank through which steam is circulated, controlled by a valve g², the water of
condensation being removed by a trap g³. Thus the bleaching liquid may be heated
either before it enters the bleaching tank or after.
The particular construction of bleaching tank C shown is designed especially for
treating paper pulp, being known as a beater engine. As usual, it has a cylinder C¹
formed with knives or paddles working against fixed knives C² beneath, and throwing
the pulp up over a dam C. The operation is the same as that of any beater engine.
The bleaching and pulp mixing and grinding operations may be conducted simul-
taneously. For removing the excess of bleaching liquid from the tank as fast as
new liquid enters, the tank is provided with the usual revolving washer or strainer F,
consisting of a wire gauze cylinder through the meshes of which the liquid can flow
but not the fibrous matter, and having internal dippers which scoop up the entering
liquid and direct it out through the discharge pipe F', from which it falls into the
hopper F2 and descends into the tank G. From this tank the brine is pumped by
the pump D through a pipe h, which lifts it and discharges it into the percolator H.
This percolator is filled with a bed of salt, through which the brine flows, so that it
dissolves the salt and is thereby strengthened. From the percolator the refortified
brine descends by a pipe h¹ and passes through the cooler E. This cooler may be
of any suitable construction, that shown consisting simply of a tank through which
the brine flows in contact with a coil of cold pipes i, these pipes carrying a stream
of cold fluid such as ice water, or preferably being cooled by a liquid which is
refrigerated by an ice machine. By this or any suitable means, the entering brine
is cooled, and passes out from the cooler through a pipe h2 back to the electrolyzer A,
which it enters again by the perforated pipe b, and is re-electrolyzed and again used
for bleaching.
Thus the bleaching operation in the tank C proceeds continuously and rapidly at
the specified temperature, the strength of the bleaching liquid being continually
fortified by drawing off a quantity of it by means of the strainer F and supplying
its place with the fresh liquid which enters from the electrolyzer. When the entire
quantity of pulp has been sufficiently bleached it is run out into a drainer where
the bleaching liquor is strained out of it, this liquor being then pumped back to the

page_text: tank G. The pulp is finally washed in a percolator to expel the remaining quantity
of bleaching liquid, and may be dried by a centrifugal machine.
In practising my process, the brine should have a density of over two degrees
Beaumé, and preferably four to six degrees, and the electrolyzer may convert from
five to ten per cent. of the brine into sodium hypochlorite. The electric energy
required will depend upon circumstances, but I have successfully employed a pressure
of from 4 to 5 volts. The continual circulation of the brine to maintain a continuous
process is not essential to my invention, as the brine may first be electrolyzed and
then run into a tank and heated, and left in contact with the matter to be bleached
for the necessary time without any circulation.
In such electrolytic processes as the foregoing, it is found that a heating action
occurs in the electrolytic cell, and that as soon as a considerable degree of heat
is manifested the electrolytic action becomes less effective, the electric energy being
apparently wasted in part in the production of heat, instead of being fully utilized
in the chemical decomposition. The object of one part of my invention is to prevent
or counteract such heating of the cell, in order to prevent waste of electric energy
and facilitate the chemical decomposition. To this end my invention provides for
the artificial cooling of the electrolyte in the cell by continually drawing it off from
the cell and passing it through a cooler in the manner already described, and
returning the cooled electrolyte to the cell, at the same time maintaining
it cool while in the cell by the application of cooling pipes or surfaces within
the cell.
In the apparatus already described, I have illustrated a coil of cooling pipes jj
applied in the upper part of the cell or electrolyzer A, to which the warmest portion
of the electrolyte rises, in order to cool this electrolyte. Through these pipes any
cold fluid may be passed such as ice-water, or cold brine. Preferably the cold
brine circuit of a refrigerating machine is applied in connection with the apparatus
in the manner shown in Figs. 1 and 2. In these figures the pipes k k constitute
a cold brine circuit. The brine is cooled in a chill tauk J, which is kept cool by
the coils of an ammonia refrigerating machine, or any other known refrigerating
apparatus. From this tank the chilled brine is pumped off by a pump K and
circulated through the circuit of pipes k, passing first through the cooling coil j
in the electrolyzer A, whereby the brine takes up some heat from the electrolyte,
after which it is passed through the cooling coils i of the cooler E, whereby the
brine takes up the heat from the warm electrolyte and cools it down to the proper
temperature for entering the electrolyzer. The brine thus warmed is then returned
to the chill tank J to be again cooled.
Fig. 6 is a side elevation mostly in vertical section illustrating the application
of my invention to an apparatus for electrolyzing sodium chloride for the
production of free chlorine and caustic soda. Fig. 7 is a sectional plan of the
electrolytic cell thereof.
The apparatus shown in these figures illustrates a useful application of this
feature of my invention. The electrolytic cell lettered A₁ is of different
construction from that first described, having a porous partition or septum m
dividing it into two chambers, in one of which is placed the anode d, and in the
other of which is placed the cathode e. The anode chamber is enclosed by a tight
fitting hood or cover n, to which is connected an outlet pipe n' for conducting
away the chlorine gas. The cathode chamber is open at top for the free escape of
the hydrogen gas, and is extended downward for the accumulation of the caustic
soda, NaHO, which is conducted off by a siphon or goose-neck p, and carried away
by a pipe p'. The brine to be electrolyzed is prepared or strengthened in the
percolator H as before described, and descends thence by a pipe to the cooler E
wherein it is cooled by contact with the cold pipes i, and then descends by a pipe h
to the anode chamber of the electrolyzer. An excess of brine is introduced, s
that a portion of it continually passes out by an overflow opening r, and descend
by the pipe to the tank G, from which it is pumped up by the pump D throug
the pipe, which conducts it back to the percolator H. In the upper part of th

page_text: recurolyzer A, 1s arranged a cooling coil of pipe ), which is connected in a brine
circuit kk as before described. The cold brine circuit includes a chill tank J for
cooling the brine, and the brine is circulated by a pump K, the cold brine flowing
first through the coil in the electrolyzer, and then through the coil i in the
cooler E, and then back to the chill tank.
For supplying the cathode_chamber with brine to take the place of that which
is decomposed, a valved pipe L may be provided leading from a separate reservoir
of brine, so that the brine thus introduced is free from chlorine.
By this process the electrolyte is maintained in constant circulation, that which
is contained in the electrolytic cell undergoing a slow movement from the inlet
to the outlet pipes, and while it remains in the cell being exposed to the cooling
action of the coil by which any heating action of the electrolytic cell is counter-
acted. The electrolysis liberates chlorine at the anode, which is confined by the
bell and passes out by the pipe n¹; caustic soda is generated in contact with the
cathode e, and by its greater specific gravity it falls to the bottom of the cell and
passes out by the pipe p. The electrolyte is first cooled in the cooler E before
entering the cell A, in which latter it is again cooled or maintained cool by the
cooler or coil j. The cooler j need not be a coil of pipe, but any other suitable
construction will answer. The cooler E may be any known construction of cooler
or attemperator, being preferably one in which the cooling medium and the
electrolyte being cooled are caused to flow past each other in opposite directions.
Fig. 8 shows the application of my present invention to the construction of a
centrifugal electrolytic cell such as that shown in my Patent No. 19,170, dated
October 25, 1892. For a description of the special construction and operation of
this cell, reference is made to that Patent. So far as my present invention is
concerned, it is only necessary to say that the centrifugal cell is provided with a coil
of pipe M, so arranged as to be just outside of the cylindrical surface assumed by
the liquid under centrifugal force, in order consequently to be immersed in the
liquid of lowest specific gravity. This coil is connected at one end by a pipe g to
a trough or channel g', while at its other end it terininates in a discharge pipes, the
liquid discharged from this pipe being caught by a stationary channel or gutter t.
The coil M may be made a part of the cold brine circuit k k shown in Fig. 6, the
brine or other cold liquid being introduced by a pipe k to the trough g', wherein
it is held by centrifugal force, and by the same force is caused to flow through the
coil M, being finally discharged by the pipe sand caught by the gutter t, from
which it flows off by the pipe k². Thus the cold liquid is circulated through the
coil M, and serves to cool the electrolyte in the centrifugal cell while the latter is
revolving.
The extent to which the electrolyte should be cooled according to my invention
cannot be stated with exactness, it being necessarily only sufficient to overcome and
counteract the heating tendency of the cell, the amount of cooling consequently
varying with the volume of current and the energy of the electrolytic action. The
electrolyte may thus be maintained at any temperature at or below the normal, the
lower the temperature the more effective being the result, except that the temperature.
should not be too close to the freezing point of the electrolyte.
My invention also provides improved electrodes or anodes for use in electrolytic
decomposition, such as electrolysis of sodium chloride either in aqueous solution as
already described or rendered liquid by fusion. In the electrolysis of chlorine
salts and some other substances, much difficulty has been experienced because of
the rapid destruction of the electrodes, particularly the anode, during the electro-
lytic action. According to my invention I use as the material for the anode an
electro-conductive metallic oxide which is substantially resistant to such products
of electrolysis of chlorine compounds as are liberated at the anode, that is, the
electro-negative products. The best examples of such metallic oxides that I have
found are magnetic iron oxide or "magnetite," Fe,O,, and iron-titanium oxide or
"ilmenite" (FeTi), O. These oxides are almost wholly unacted upon during the
electrolysis of an aqueous solution of sodium chloride. They have the advantage
n

page_text: of being good conductors, and when used as the anode do not speck or discolor the
electrolyte, and have great durability against corrosion or disintegration; in fact
I have found that the longer they are used the less they are affected.
The iron or analogous oxides (as magnetite or ilmenite) may be used in the
form in which they occur as minerals, by sawing or otherwise shaping the mineral
into a slab, cylinder or other desired shape. Or it is within my invention to cast
the oxide into the desired shape for the electrode by adding to it a sufficient
proportion of suitable fluxing agents, such as silica, lime and magnesia, to enable
it to be fused and caused to flow, but such fluxes being non-conductors, should
not be in such large proportion as to materially impair the electric conductivity of
the electrode. I have successfully used a composition known as "black slag
from pig iron furnaces, which consists chiefly of a magnetic iron oxide or oxides,
with a small proportion of various fluxing ingredients, enabling it to be fused
and cast.
My improved anode can be used in the electrolysis of aqueous solutions, or of
molten or fused electrolytes. In the latter case, the electrolyte may be fused by
heat externally applied, or if it offers sufficient resistance to the passage of the
electric current through it, the heat thus generated may serve to keep it fused.
My new electrode may be used in the electrolysis of other substances than chlorine
compounds, being especially advantageous in any case where the electrolytic process
develops a powerful oxidizing action at the anode.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
1. The described process of bleaching characterized by electrolyzing a solution
of a chloride of an alkali or alkaline earth, heating the electrolyte containing the
resulting hypochlorite to 130 degrees Fahrenheit or upwards, and bleaching with
it while at such elevated temperature, whereby the bleaching operation is expedited,
substantially as set forth.
2. The process of bleaching characterized by first electrolyzing a solution of a
chloride of au alkali o alkaline earth, heating the electrolyte containing the
resulting hypochlorite and bleaching with it while at an elevated temperature, then
cooling it and again electrolyzing it, whereby the bleaching is performed at a
high temperature and the electrolysis at a low temperature, essentially as set
forth.
3. The described continuous electrolytic bleaching process consisting in first
electrolyzing a solution of a chloride of an alkali or alkaline earth by circulating it
through an electrolyzer, heating the electrolyte containing the resulting hypochlorite,
bleaching with it while at an elevated temperature, continuously drawing off the
electrolyte from the material being bleached, cooling it, and returning it to the
electrolyzer, essentially as set forth.
4. The improvement in electrolytic processes, which consists in first cooling the
electrolyte, then introducing it to an electrolyzer, there subjecting it to electrolysis,
and again cooling it during the electrolysis, essentially as set forth.
5. The improvement in electrolytic processes, which consists in artificially
cooling the electrolyte by circulating a cold liquid first through passages in an
electrolyzer, and then through a preliminary cooler, the electrolyte being first
cooled in the latter and then introduced into the cell.
6. The described anode for use in electrolytic decompositions, consisting
essentially of electro-conductive oxide of iron of dense impermeable character,
substantially as set forth.
7. The described anode for use in electrolytic decompositions, consisting of a
conducting body having an exposed surface of electro-conductive oxide of iron of
dense impermeable character, substantially as set forth.
8. An anode for use in electrolytic decompositions consisting essentially of
magnetic iron oxide.

page_text: 9. An anode for use in electrolytic decompositions consisting of a composition of
an electro-conductive iron oxide and a binding agent in the nature of a flux.
10. The described electrode consisting of the composition of electro-conductive
iron oxide and fluxing materials known as black slag.
11. The combination in an electrolytic apparatus with a receptacle for the
electrolyte and a cathode, of an anode consisting of dense impermeable magnetic.
iron oxide, substantially as set forth.
12. The described anode for use in electrolytic decompositions, consisting
essentially of titanic iron oxide or ilmenite, (FeTi),O,, substantially as set forth.
Dated this Second day of March 1896.
J. C. MEWBURN & ELLIS,
55 & 56 Chancery Lane, London, Chartered Patent Agents.