IMPROVEMENTS IN BLEACHING AND APPARATUS THEREFOR
Year: 1884

page_text: This Specification was, upon the 10th day of May, 1887, amended under
Sections 18 to 21 of the Patents, Designs, and Trade Marks Act, 1883.
כל
I JOHN HENRY JOHNSON of 47 Lincoln's Inn Fields in the County of Middlesex
Gentleman do hereby declare the nature of the said Invention for "IMPROVEMENTS
IN BLEACHING AND APPARATUS THEREFOR which Invention has been com-
municated to me, from abroad by Eugène Hermite of Paris in the Republic of
France Chemist to be as follows:-
This Invention relates to an improved process and apparatus for bleaching yarn.
textile fabrics paper pulp and the like and it consists in the employment as lierein-
after described of the chemical reactions resulting from the electrolysis or electrical
docomposition of the chlorides of magnesium calcium and aluminium but preferably
of chloride of magnesium. These reactions are extremely complex and generate a
sories of salts of magnesia, the acids of which consist of oxygenated combinations
of chlorine-It appears that the chloride say of magnesium is decomposed producing
what may be termed hypochlorate of magnesia which in its turn forms chlorate
and chlorite of magnesia. By the action of the electric current these two salts are
also decomposed and their acids set at liberty. The reaction which takes place may
be represented by the following equations namely:
2 (Mg. Cl+5 HO) = 2 (Mg O. CIO) + 10 H
2 (Mg O. CI 0) = Mg O. CI 0. + Mg O. CI O'
Mg O. CI O + Mg O. CI 03 C10' + CI 0³.
=====
The resulting chloric and chlorous acids in presence of the organic matter or
materials to be bleached upon which they act as decolorising agents, transfer to
the latter their oxygen and the fixed chlorine of the hydrogen forming hydrochloric
acid which combines with the free magnesia so as to reconstitute the chlorine of
the original magnesium.
A solution of electrolysed chloride of magnesium possesses a much greater
decolourising power than hypochlorite of lime for example containing the same
amount of chlorine. The valuable results obtained by the improved process may
also be attributed to a certain extent to the nascent condition in which the agents
are employed.

page_text: The same liquid may be used again and again by subjecting it to another process
of electrolysis after each bleaching operation.
The solution of chloride of magnesium which it is preferred to employ in carrying
out this Invention is of a specific gravity of about 1.125 or marking a density of
about 16 degrees Beaumé as the solution of this salt attains its maximum of
conducting power at this degree of density.
The polarization in open circuit is about 2 volts 13 and the specific resistance of
the solution of chloride of magnesium at 1·125 density at a temperature of
30 degrees Centigrade is about 6 Ohms 1. When a solution of chloride of calcium
is employed the density should be about 1-191 or twenty three degrees Beaumé.
The apparatus employed in carrying out this improved Bleaching process is
preferably constructed as next hereinafter described.
The said apparatus is provided with brickwork troughs or tanks cemented over
the whole of their internal surface. A wooden framework is arranged above these
troughs and supports rollers which are driven by worms and worm wheels and
carry the materials to be operated upon.
These troughs contain the bleaching solution which is subjected to electrolysis
by means of a suitable number of electrodes suspended therein. The negative
electrodes consist preferably of zinc plates bolted together and soldered to copper
rods connected with the main conductor being insulated from the liquid by a
varnish or india rubber covering. The positive electrodes are constituted by a
plate of carbon platinum. or other material capable of resisting the action of
chlorine or of its oxygenated compounds and are carried in wood frames. A copper
rod connected with the main conductor is soldered to one extremity of each
of these electrodes. Recesses or cavities are formed in the frames arround the
copper connecting rods and are filled up with melted sulphur which completely
insulates and protects the soldered joints the other parts of the rods being protected
by an india rubber covering.
The troughs are provided with a supply pipe for supplying the solution of
chloride of magnesium calcium or aluminium from a suitable cistern or reservoir
and an outlet conduit is employed for carrying the liquid away from the troughs
to another cistern where it is allowed to settle after each operation and is then
pumped back to the supply cistern for reuse.
Any suitable mechanical arrangement may he employed for immersing the
materials in the liquid. When frames or rods are employed the materials are
hung upon rods or rails supported by a suitable frame work of transverse bars-anil
supports suspended by a chain from a pulley to which an alternating motion may
he imparted by an excentric so as to shake or agitate the hanks or materials in the
liquid in the troughs. A crane or hoist arranged at one side serves to remove the
framework together with the materials.
In dealing with hanks of yarn or thread as well as with textile fabrics the
liquid may be prepared in advance in a series of tanks contents of which are.
collected in a single trough where the bleaching is effected. The preparing tanks
being arranged in series (preferably in sets of about forty) any desired number
may be connected in tension provided that the electro-motive force is sufficient to
overcome the resistance and the polarisation of the united troughs. A key for
reversing the current may be employed with advantage in the circuit thereby
enabling the negative plates to be occasionally connected with the positive pole for
a few moments for the purpose of detaching any deposit that may have formed
upon the said plates.
Paper pulp may be bleached according to this Invention by subjecting a solution
of chloride of magnesium calcium or aluminium to electrolysis in a series of
preparing backs or vais connected in series and provided with electrodes as herein-
before described. When the liquid is sufficiently charged with the decolourising
principle it is drawn off into a large tank and is employed in the usual manner in
the bleaching apparatus but directly the bleaching is concluded the pulp must bo
carefully drained and the liquid pumped back into the electrolysing tanks where it

page_text: is again exposed to the action of the electric current and is then ready for another
operation.
If preferred the solution may be subjected to electrolysis in the presence of the
pulp or materials either with or without undergoing electrolysis in separato
vessels.
In place of the pallets or blades usually employed in treating pulp I prefer to
place a helix transversely at one end of the vat thereby enabling the apparatus to
be closed in.
Chloride of lime may be employed concurrently with chloride of magnesium and
it is advantageous to add a certain quantity of magnesia lime or alumina to the
solution according to the chloride employed.
One of the chief advantages of this. Invention is that it enables the most delicate
textile materials to be bleached without injuring the fibre.
The electrolysed solution or liquor possessing great decolourising power acts even
when it contains a relatively small quantity of these chlorine compounds and as
the production of these chlorine compounds can be absolutely controlled or regulato
as required by adjusting the electric current the bleaching action is perfectly under
control.
J. HENRY JOHNSON,
47, Lincoln's Inn Fields, London, W.C.

page_text: COMPLETE SPECIFICATION (AMENDED).
Improvements in Bleaching and Apparatus therefor.
25
JOHN HENRY JOHNSON of 47 Lincoln's Inn Fields in the County of Middlesex
Gentleman do hereby declare the nature of the said Invention for "IMPROVEMENTS
IN BLEACHING AND APPARATUS THEREFOR which Invention has been com-
municated to me from abroad by Eugène Hermite of Paris in the Republic of
France Chemist 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 to an improved process and apparatus for bleaching textile
fabrics, yarns, thread, paper pulp and the like and it consists in the employment of
the chemical reactions resulting from the electrical decomposition of eertain sults or
bleaching agents hereinafter specified (chlorides of magnesium enleium or aluminium)
Thesseis salts or as a bleaching agents are is subjected to electrolysis by the aid of
platinum electrodes arranged and operating as hereinafter described and are is
continually regenerated for reuse.
And in order that the said Invention may be fully understood I shall now
proceed more particularly to describe the same and for that purpose shall refer to
the several figures on the annexed sheets of drawings the same letters of reference
indicating corresponding parts in all the corresponding figures.
Figure 1 of the accompanying drawings represents a vertical section and
Figure 2a plan of an apparatus employed in bleaching according to this Invention.
The said apparatus is provided with brickwork troughs or tanks A separated by
brick partitions and cemented over the whole of their internal surface. These
troughs contain the bleaching solution. A wooden framework A' is arranged
above these troughs and supports rollers B which are driven by worms and worm
wheels and carry the materials to be bleached. Supports S are arranged between
the rollers B for the purpose of supporting the said rollers when being filled or
emptied. This arrangement of the upper part of the apparatus resembles that
commonly employed.
The solution in the troughs A is subjected to electrolysis by means of electrodes
suspended therein.
Figure 3 represents one of the negative electrodes which consist preferably of
zine plates (bolted together as indicated in Figure 6 by bolts passed through holes t
and soldered to copper rods e connected with the main conductor being insulated
from the liquid by a suitable varnish or india rubber covering. The positive
electrodes one of which is shown separately in Figure 4 are constituted by plates D
of platinum carried in wood frames D' as indicated in figures 4 and 5. A copper
rod d connected with the main conductor is soldered to one extremity of each of
these electrodes. Recesses or cavities are formed in the frames around the rods d

page_text: and are filled up with an insulating compound as indicated at figures 5.and 6
which completely insulates and protects the soldered joints the other parts of the
rods being protected by an india rubber covering Figure 6 represents a number
of positive and negative electrodes connected together as employed in the bleaching
troughs A. The number of electrodes employed necessarily varies with the
intensity of the current which is to be caused to pass in the bath with a minimum
expenditure of electro-motive force.
Figure 2 shows the connection and arrangement of the conductors constituted by
copper bars and placed upon the edges of the tanks and connected to the rods d
and c of the electrodes. The same figure also shows a supply pipe T employed for
supplying the troughs A with the solution of chloride of magnesium from a
reservoir E and an outlet conduit V employed for carrying the liquid which has
been used away from the troughs A to a cistern F where it is allowed to settle.
The clear liquid is afterwards pumped back into the reservoir E by a pump
placed at H.
In place of the rollers B any other suitable device such as frames or rods may be
employed for immersing the materials in the liquid the apparatus undergoing
no alteration except in respect of the height of the troughs but there should always
be as many troughs as there are frames or rollers.
Figures 8 and 9 represent in longitudinal and transverse section respectively a
portion of an apparatus in which the goods are suspended from rods or frames.
Above the compartments or brickwork troughs A each containing a set of
electrodes a there is provided a frame, B fitted with rods 6 supporting the goods
or thread to be treated. These rods are supported at the middle by a bar d which
in turn is supported by a bar e forming part of a frame work carrying all the
frames B. The frame work C a portion of which is shown in plan in figure 10 is
suspended by a chain from a pulley to which an alternating motion is imparted by
an excentric so as to shake or agitato the hanks or goods in the liquid in the
troughs A. A crane or hoist not shown in the drawing arranged at one side serves
to remove the framework together with the goods after each operation and
transports it to a place where the moisture is drained off.
This process is equally applicable to bleaching fabrics composed of linen, cotton,
hemp china-grass and other fibres and any suitable mechanical arrangement may
be employed for passing the cloths or goods through the bleaching tanks or troughs.
In dealing with hanks of yarn or thread as well as with textile fabrics the liquid
may be prepared in advance in a series of tanks the contents of which are collected
in a single trough where the bleaching is effected. The preparing tanks being
arranged in series (preferably in sets of about twenty each) any desired number of
such tanks may be connected in tension provided that the electro motive force at
the terminals of the dynamo or generator is sufficient to overcome the resistance
and polarization of the united troughs. When the bleaching operation is completed the
liquid is returned to the preparing tanks.
A key or switch for reversing the current may be employed with advantage in
the circuit thereby enabling the negative plates to be occasionally connected with
the positive pole for a few moments for the purpose of detaching any deposit that
may have formed upon the said plates.
Paper pulp may be bleached according to this Invention in three ways viz :-
The
1. By subjecting a solution of the salt employed to electrolysis in a series of backs
or vats A¹ figure 7 containing electrodes connected in tension and arranged as
hereinbefore described with reference to figures 1 and 2. When the liquid is
sufficiently charged with the decolourising principle it is drawn off into a large
tank by opening suitable cocks communicating with cach preparing vat.
liquid thus prepared is employed in the usual manner in the bleaching troughs or
apparatus but directly the bleaching is concluded the pulp must be carefully
drained and the liquid pumped back into the electrolysing tanks where it is again
exposed to the action of the electric current and is then ready for another
operation.

page_text: .
2. By effecting the bleaching operation in bleaching vats or apparatus containing
a series of electrodes arranged as hereinbefore described. In this case the solution
of the salt is mixed with the paper pulp and an electric current of sufficient
intensity is then caused to pass through the materials. After each bleaching
operation the liquid is drawn off for reuse in subsequent operations.
3. By combining the two methods hereinbefore described. According to this
third method which is recommended in preference to the first and second the
bleaching vats provided with electrodes are arranged in tension in combination
with a series of preparing troughs or backs and the liquid from these backs is
caused to circulate in the bleaching vats care being taken to employ a current
possessing the requisite intensity and electro-motive power. In place of the pullets
or blades usually employed-it-is-preferred to-substitute-a-helix at one end-of
the vat.
It has been ascertained by experiment that the decomposition of chloride of
magnesium by an electric current is attended with an extremely complex action
and generates an entire series of salts of magnesia the acids of which consist of
oxygenated combinations of chlorine. In the series of processes that take place in
this operation it would appear that the chloride of magnesium is first decomposed
producing hypochloric acid and magnesia but immediately on coming into the
presence of the base this acid splits into chloric and chlorous acid which combine
with the magnesia and form chlorate and chlorite of magnesia. These two salts
are also decomposed by the action of the current and their acids are set froo whilst
the magnusia passes to the negative pole. The chloric and chlorous acids in
presence of the colouring matter transfer to the latter their oxygen which
decolourises it whilst the chlorine absorbes hydrogen forming hydro-chloric acid and
recombining with the magnesia in the condition of chloride of magnesium. This.
salt under the influence of the electric current is subjected to the foregoing processes
of decomposition and combination invariably reverting to the condition of chloride
of magnesium. The multiple changes that take place may be expressed by the
following equations.
The CO and C1 03 part with their oxygen in the presence of the colouring
matter the chlorine fixing hydrogen and forming hydrochloric acid which recombines
with the magnesia and reconstitutes the original salt Mg C.
A solution of electrolysed chloride of magnesium possesses a great decolourising
power. It has been ascertained by experiment that in treating one kilogramme of
linen thread which has undergone no washing the quantity of chlorine measured
chlorometrically is required to be about 114 grammes when employed according
to this Invention whereas about one hundred grammes of chlorine are required in
order to bleach the same quantity of washed thread (thread treated with lye) by
the ordinary method of treatment with hypochlorite of lime. In the presence of
the organic matter which colours the textile material or fibre the oxygenated
compounds of chlorine become converted into hydrochloric acid which combines
with the magnesia thereby reconstituting chloride of magnesium. This fact has
moreover already been demonstrated in the reaction of hypochlorite of lime upon
colouring matter. The same liquid is consequently enabled to be used again and
again by repeating the process of electrolysis after each bleaching operation.
When it is considered that chlorine or its oxygenated compounds invariably
combine with the colouring matter before acting upon the cellulose it will be evident
that by means of my improved process it is possible to bleach textile materials
without prejudice to the strength or solidity of the fibres it being sufficient to

page_text: regulate the intensity of the electric current in accordance with the degree of
whiteness to be obtained. In treating flax thread for example according to this
invention the waste or loss amounts to only from about six to eight per cent of the
weight of the thread, the loss when the ordinary process is employed being from
fourteen to eighteen per cent.
A solution of chloride of calcium cubjected to electrolysis under the same
conditions also produces a very powerful decolourising principle although inferior to
the chloride of magnesium which is employed by preference for the purposes-of
this invention.
The electrolysis of chloride of aluminium in solution also gives rise to remarkable
and novel reactions and in certain cases it is found advantageous to employ it as
the bleaching agent.
I will now proceed to describe the method of In carrying out the bleaching process
according to this invention, the solution of chloride of magnesium employed by
preference is of a specific gravity of about 1125 or a density of about 16 degrees
Beaumé as the solution of this salt attains its maximum of conducting power in
this condition. The polarization in open circuit is about 2-13 volts and the specific
resistance at a density of 1125 and a temperature of 30° Centigrade is 6.1 ohms.
I have stated that chloride of calcium may be employed for the In my bleaching
process in place of the chloride of magnesium but preference is given to the latter this
salt being is more advantageous than chloride of calcium for many reasons, namely
for instance-A solution of chloride of magnesium is a better conductor at a low
degree of concentration and thus diminishes the waste in the treatment. The chloride
of magnesium of commerce is in a state of greater purity than the chloride of calcium
of commerce. It is a well established fact that salts resulting from the combination
of an oxygenated compound of chlorine with magnesia possess a greater decolorising
capacity than the corresponding salfs of lime. For example hypochlorite of magnesia
is a more powerful decolourising agent than hydrochlorite of lime. Moreover
magnesia does not injure textile, materials or fabrics whereas lime ontirely destroys
them. Nevertheless in certain localities chloride of lime may be employed with
advantage concurrently with chloride of magnesium especially when it is to be
obtained at a low price. The density of the colution of chloride of ouleinm should
be 1.101 or twenty three degrees Beaume. At this degree of concentration the solution
of chloride of calcium-presents the least resistance to the passage of the electric
current its specific resistance in this condition at a temperature of thirty degrees
centigrade being 1.0 ohms.
But besides all this, I have found from experience that my process cannot be usefully
and commercially worked except with chloride of magnesium and I therefore disclaim the
use of other chlorides in my process.
One of the chief advantages of this process is that it enables the most delicate
textile materials to be bleached without injuring the fibre.
The electrolysed
solution of chloride of magnesium. possessing great decolourizing power acts even
when it contains a relatively small quantity of these chlorine compounds and as
the production of these chlorine compounds can be absolutely controlled or regulated
as required by adjusting the electric current the bleaching action is perfectly under
control.
Having now particularly described and ascertained the nature of the said
Invention and in what manner the same is to be performed I declare that I make no
general claim to the use of chlorides under electrolytic action for leaching nor to the use
of chloride of magnesium unless it is employed as heretofore described in such a manner
as to admit of its continuous decomposition and regeneration but what I claim is :
:-
First The employment in apparatus for bleaching by electrolysis of platinum
electrodes arrangeil and connected substantially as hereinbefore described and
illustrated in the accompanying drawings.

page_text: Second-The employment for bleaching purposes in general the manner described
of the reactions produced by the electrical decomposition of the salts or bleaching
agents herein before specified the said sults or bleaching agents admitting of
and continual regeneration substantially of chloride of magnesium as hereinbefore
described.
=
Third: The several methods and combinations of apparatus for bleaching paper
pulp substantially as hereinbefore described.
Dated this 21st day of July 1885.
J. HENRY JOHNSON,
47, Lincoln's Inn Fields, London, W.C.

page_text: I JOHN HENRY JOHNSON of 47 Lincoln's Inn Fields, in the County of Middlesex
Gentleman do hereby declare the nature of the said Invention for "IMPROVEMENTS
IN BLEACHING AND APPARATUS THEREFOR "
which Invention has been com-
municated to me from abroad by Eugène Hermite of Paris in the Republic of
France Chemist to be as follows:-
This Invention relates to an improved process and apparatus for bleaching yarn
textile fabrics paper pulp and the like and it consists in the employment as herein-
after described of the chemical reactions resulting from the electrolysis or electrical
decomposition of the chlorides of magnesium calcium and aluminium but preferably
of chloride of magnesium. These reactions are extremely complex and generate a
series of salts of magnesia, the acids of which consist of oxygenated combinations
of chlorine-It appears that the chloride say of magnesium is decomposed producing
what may be termed hypochlorate of inagnesia which in its turn forms chlorate
and chlorite of magnesia. By the action of the electric current these two salts are
also decomposed and their acids set at liberty. The reaction which takes place may
be represented by the following equations namely :-
2 (Mg. Cl + 5 HO) = 2 (Mg O. CI O) + 10 H
2 (Mg O. Cl 0*) Mg O. CI 0. + Mg O. CI 0³
Mg O. CI O + Mg O. CI 0³ CHO° + C1 O
=
==
The resulting chloric and chlorous acids in presence of the organic matter or
materials to be bleached upon which they act as decolorising agents, transfer to
the latter their oxygen and the fixed chlorine of the hydrogen forming hydrochloric
acid which combines with the free magnesia so as to reconstitute the chlorine of
the original magnesium.
A solution of electrolysed chloride of magnesium possesses a much greater
decolourising power than hypochlorite of line for example containing the same
amount of chlorine. The valuable results obtained by the improved process may.
also be attributed to a certain extent to the nascent condition in which the agentsi
are employed.
J
)

page_text: The same liquid may be used again and again by subjecting it to another process
of electrolysis after each bleaching operation.
The solution of chloride of magnesiumn which it is preferred to employ in carrying.
out this Invention is of a specific gravity of about 1125 or marking a density of
about 16 degrees Beaumé as the solution of this salt attains its maximum of
conducting power at this degree of density.
The polarization in open circuit is about 2 volts 13 and the specific resistance of
the solution of chloride of magnesium at 1125 density at a temperature of
30 degrees Centigrade is about Ohms 1. When a solution of chloride of calcium
is employed the density should be about 1.191 or twenty three degrees Beaumné.
The apparatus employed in carrying out this improved bleaching process is
preferably constructed as next hereinafter described.
The said apparatus is provided with brickwork troughs or tanks cemented over
the whole of their internal surface. A wooden framework is arranged above these
troughs and supports rollers which are driven by worms and worm wheels and
carry the materials to be operated upon.
These troughs contain the bleaching solution which, is, subjected to electrolysis
by means of a suitable number of electrodes suspended therein. The negative
electrodes consist preferably of zinc plates bolted together and soldered to copper
rods. connected with the main conductor being insulated from the liquid by a
varnish or india rubber covering. The positive electrodes are constituted by a
plate of carbon platinum or other material capable of resisting the action of
chlorine or of its oxygenated compounds and are carried in wood frames. A copper
rod connected with the pain conductor is soldered to one extremity of each
of these electrodes. Recesses or cavities are formed in the frames arround the
copper connecting rods and are filled up with melted sulphur which completely
insulates and protects the soldered joints the other parts of the rods being protected
by an india rubber covering.
The troughs are provided with a supply pipe for supplying the solution of
chloride of magnesium calcium or aluminium from a suitable cistern or reservoir
and an outlet conduit is employed for carrying the liquid away from the troughs
to another cistern where it is allowed to settle-after each operation and is then
pumped back to the supply cistern for reuse.
Any suitable mechanical arrangement may be employed for immersing the
materials in the liquid. When frames or rods are employed the materials are
hung upon rods or rails supported by a suitable frame work of transverse bars and
supports suspended by a chain from a pulley to which an alternating motion may
be imparted by an excentric so as to shake or agitate the hanks or materials in the
liquid in the troughs. A crane or hoist arranged at one side scives to remove the
framework together with the materials.
In dealing with hanks of yarn or thread as well as with textile fabrics the
liquid may be prepared in advance in a series of tanks contents of which are
collected in a single trough where the bleaching is effected. The preparing tanks
being arranged in series (preferably in sets of about forty) any desired number
may be connected in tension provided that the electro-motive force is sufficient to
overcome the resistance and the polarisation of the united troughs. A key for
reversing the current may be employed with advantage in the circuit thereby
enabling the negative plates to be occasionally connected with the positive pole for
a few moments for the purpose of detaching any deposit that may have formed
upon the said plates.
Paper pulp may be bleached according to this Invention by subjecting a solution
of chloride of magnesium calcium or aluminium to electrolysis in a series of
preparing backs or vats connected in series and provided with electrodes as herein-
before described. When the liquid is sufficiently charged with the decolourising
principle it is drawn off into a large tank and is employed in the usual manner in
the bleaching apparatus but directly the bleaching is concluded the pulp must be
carefully drained and the liquid pumped back into the electrolysing tanks where it.

page_text: is again exposed to the action of the electric current and is then ready for another
operation.
If preferred the solution may be subjected to electrolysis in the presence of the
pulp or materials either with or without undergoing electrolysis in separate
vessels.
In place of the pallets or blades usually employed in treating pulp I prefer to
place a helix transversely at one end of the vat thereby enabling the apparatus to
be closed in.
Chloride, of lime may be employed concurrently with chloride of magnesium and
it is advantageous to add a certain quantity of magnesia lime or alumina to the
solution according to the chloride employed.
One of the chief advantages of this Invention is that it enables the most delicate
textile materials to be bleached without injuring the fibre.
The electrolysed solution or liquor possessing great decolourising power acts even
when it contains a relatively small quantity of these chlorine compounds and as
the production of these chlorine compounds can be absolutely controlled or regulated
as required by adjusting the electric current the bleaching action is perfectly under
control.

page_text: 33
I JOHN HENRY JOHNSON of 47 Lincoln's Inn Fields in the County of Middlesex
Gentleman do hereby declare the nature of the said Invention for "IMPROVEMENTS
IN BLEACHING AND APPARATUS THEREFor which Invention has been com-
municated to me from abroad by Eugène Hermite of Paris in the Republic of
France Chemist 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 to an improved process and apparatus for bleaching textile
fabrics, yarns, thread, paper pulp and the like and it consists in the employment of
the chemical reactions resulting from the electrical decomposition of certain salts or
bleaching agents hereinafter specified (chlorides of magnesium calcium or aluminium)
These salts or bleaching agents are subjected to electrolysis by the aid of platinum
electrodes arranged and operating as hereinafter described and are continually
regenerated for reuse.
And in order that the said Invention may be fully understood. I shall now
proceed more particularly to describe the same and for that purpose shall refer to
the several figures on the annexed sheets of drawings the same letters of reference
indicating corresponding parts in all the corresponding figures.
Figure 1 of the accompanying drawings represents a vertical section and
Figure 2 a plan of an apparatus, employed in bleaching according to this Invention.
The said apparatus is provided with brick work troughs or tanks A separated by
brick partitions and cemented over the whole of their internal surface. These
troughs contain the bleaching solution. A wooden framework A¹ is arranged
above these troughs and supports rollers B which are driven by worms and worm
wheels and carry the materials to be bleached. Supports S are arranged between
the rollers B for the purpose of supporting the said rollers when being filled or
emptied. This arrangement of the upper part of the apparatus resembles that
commonly employed.
The solution in the troughs A is subjected to electrolysis by means of electrodes
suspended therein.
Figure 3 represents one of the negative electrodes which consist preferably of
zinc plates C bolted together as indicated in Figure 6 by bolts passed through holest
and soldered to copper rods c connected with the main conductor being insulated
from the liquid by a suitable varnish or india rubber covering. The positive
electrodes one of which is shown separately in Figure 4 are constituted by plates D
of platinum carried in wood frames D¹ as indicated in figures 4 and 5. A copper
rod a connected with the main conductor is soldered to one extremity of each of
these electrodes. Recesses or cavities are formed in the frames around the rods d
and are filled up with an insulating compound as indicated at a figures 5 and
which completely insulates and protects the soldered joints the other parts of the
rods being protected by an india rubber covering Figure 6 represents a number
of positive and negative electrodes connected together as employed in the bleaching
troughs A. The number of electrodes employed necessarily varies with the
intensity of the current which is to be caused to pass in the bath with a minimum
expenditure of electro-motive force.

page_text: Figure 2 shows the connection and arrangement of the conductors constituted by
copper bars band 6 placed upon the edges of the tanks and connected to the rods d
and c of the electrodes. The same figure also shows a supply pipe T employed for
supplying the troughs A with the solution of chloride of magnesium from a
reservoir E and an outlet conduit V employed for carrying the liquid which has
been used away from the troughs A to a cistern F where it is allowed to settle.
The clear liquid is afterwards pumped back into the reservoir E by a pump.
placed at H
.In place of the rollers B any other suitable device such as frames or rods may be
employed for immersing the materials in the liquid the apparatus undergoing.
no alteration except in respect of the height of the troughs but there should always
be as many troughs as there are frames or rollers.
Figures 8 and 9 represent in longitudinal and transverse section respectively a
portion of an apparatus in which the goods are suspended from rods or frames.
Above the compartments or brickwork troughs A each containing a set of
electrodes a there is provided a frame B fitted with rods b supporting the goods
or thread to be treated. These rods are supported at the middle by a bar & which
in turn is supported by a bar e forming part of a frame work C carrying all the
frames B. The frame work C a portion of which is shown in plan in figure 10 is
suspended by a chain from a pulley to which an alternating motion is imparted by
an excentric so as to shake or agitate the hanks or goods in the liquid in the
troughs A. A crane or hoist not shown in the drawing arranged at one side serves.
to remove the framework together with the goods after each operation and
transports it to a place where the moisture is drained off.
.
This process is equally applicable to bleaching fabrics composed of linen, cotton,
hemp china-grass and other fibres and any suitable mechanical arrangement may
be employed for passing the cloths or goods through the bleaching tanks or troughs.
In dealing with hanks of yarn or thread as well as with textile fabrics the liquid
may be prepared in advance in a series of tanks the contents of which are collected
in a single trough where the bleaching is effected. The preparing tanks being
arranged in series (preferably in sets of about twenty each) any desired number of
such tanks may be connected in tension provided that the electro motive force at
the terminals of the dynamo or generator is sufficient to overcome the resistance
and polarization of the united troughs.
A key or switch for reversing the current may be employed with advantage in
the circuit, thereby enabling the negative plates to be occasionally connected with
the positive pole for a few moments for the purpose of detaching any deposit that
may have formed upon the said plates.
The
Paper pulp may be bleached according to this Invention in three ways viz :—
1. By subjecting a solution of the salt employed to electrolysis in a series of backs
or vats A¹ figure 7 containing electrodes connected in tension and arranged as
herein before described with reference to figures 1 and 2. When the liquid is
sufficiently charged with the decolourising principle it is drawn off into a large
tank by opening suitable cocks communicating with each preparing vat.
liquid thus prepared is employed in the usual manner in the bleaching troughs or
apparatus but directly the bleaching is concluded the pulp must be carefully
drained and the liquid pumped back into the electrolysing tanks where it is again
exposed to the action of the electric current and is then ready for another
operation.
2. By effecting the bleaching operation in bleaching vats or apparatus containing
a series of electrodes arranged as herein before described. In this case the solution
of the salt is mixed with the paper pulp and an electric current of sufficient
intensity is then caused to pass through the materials. After each bleaching
operation the liquid is drawn off for reuse in subsequent operations.
3. By combining the two methods herein before described. According to this
third method which is recommended in preference to the first and second the
bleaching vats provided with electrodes are arranged in tension in combination

page_text: with a series of preparing troughs or backs and the liquid from these backs is
caused to circulate in the bleaching vats care being taken to employ a current
possessing the requisite intensity and electro-motive power. In place of the pallets
or blades usually employed it is preferred to substitute a helix at one end of
the vat.
It has been ascertained by experiment that the decomposition of chloride of
magnesium by an electric current is attended with an extremely complex action
and generates an entire series of salts of magnesia the acids of which consist of
oxygenated combinations of chlorine. In the series of processes that take place in
this operation it would appear that the chloride of magnesium is first decomposed
producing hypochloric acid and magnesia but immediately on coming into the
presence of the base this acid splits into chloric and chlorous acid which combine
with the magnesia and form chlorate and chlorite of magnesia. These two salts
are also decomposed by the action of the current and their acids are set free whilst
the magnesia passes to the negative pole. The chloric and chlorous acids in
presence of the colouring matter transfer to the latter their oxygen which
decolourises it whilst the chlorine absorbes hydrogen forming hydro-chloric acid and
recombining with the magnesia in the condition of chloride of magnesium. This
salt under the influence of the electric current is subjected to the foregoing processes
of decomposition and combination invariably reverting to the condition of chloride
of magnesium. The multiple changes that take place may be expressed by the
following equations.
2 (Mg Cl, 5 HO)
=
2 Mg Cl + 10 HO =.
2 Mg O + 2 Cl O' + 10 H = Mg O CI O + MgO C1 0³ =
UGTEU ITU TONG
The two equivalents of Mg pass to the negative pole decomposing the water and
forming magnesia.
The Cl O and CI O³ part with their oxygen in the presence of the colouring
matter the chlorine fixing hydrogen and forming hydrochloric acid which recombines
with the magnesia and reconstitutes the original salt Mg Cl.
A solution of electrolysed chloride of magnesium possesses a great decolourising
power. It has been ascertained by experiment that in treating one kilogramme of
linen thread which has undergone no washing the quantity of chlorine measured
chlorometrically is required to be about 114 grammes when employed according
to this Invention whereas about one hundred grammes of chlorine are required in
order to bleach the same quantity of washed thread (thread treated with lye) by
the ordinary method of treatment with hypochlorite of lime. In the presence of
the organic matter which colours the textile material or fibre the oxygenated
compounds of chlorine become converted into hydrochloric acid which combines
with the magnesia thereby reconstituting chloride of magnesium. This fact has
moreover already been demonstrated in the reaction of hypochlorite of lime upon
colouring matter. The same liquid is consequently enabled to be used again and
again by repeating the process of electrolysis after each bleaching operation.
When it is considered that chlorine or its oxygenated compounds invariably
combine with the colouring matter before acting upon the cellulose it will be evident
that by means of my improved process it is possible to bleach textile materials
without prejudice to the strength or solidity of the fibres it being sufficient to
regulate the intensity of the electric current in accordance with the degree of
whiteness to be obtained. In treating flax thread for example according to this
invention the waste or loss amounts to only from about six to eight per cent of the
weight of the thread, the loss when the ordinary process is employed being from
fourteen to eighteen per cent.
A solution of chloride of calcium subjected to electrolysis under the same
conditions also produces a very powerful decolourising principle although inferior to
the chloride of magnesium which is employed by preference for the purposes of
this invention.

page_text: The electrolysis of chloride of aluminium in solution also gives rise to remarkable
and novel reactions and in certain cases it is found advantageous to employ it as
the leaching agent.
I will now proceed to describe the method of carrying out the bleaching process
according to this invention. The solution of chloride of magnesium employed by
preference is of a specific gravity of about 1.125 or a density of about 16 degrees
Beaumé as the solution of this salt attains its maximum of conducting power in
this condition. The polarization in open circuit is about 2.13 volts and the specific
resistance at a density of 1125 and a temperature of 30° Centigrade is 6.1 ohms.
I have stated that chloride of calcium may be employed for the bleaching process
in place of the chloride of magnesium but preference is given to the latter this salt
being more advantageous for many reasons namely: A solution of chloride of
magnesium is a better conductor at a low degree of concentration and thus
diminishes the waste in the treatment. The chloride of magnesium of commerce
is in a state of greater purity than the chloride of calcium of commerce.
It is a
well established fact that salts resulting from the combination of an oxygenated
compound of chlorine with magnesia possess a greater decolorising capacity than
the corresponding salts of lime. For example hypochlorite of magnesia is a more
powerful decolourising agent than hydrochlorite of lime. Moreover magnesia does
not injure textile materials or fabrics whereas lime entirely destroys them. Never-
theless in certain localities chloride of lime may be employed with advantage
concurrently with chloride of magnesium especially when it is to be obtained at a
low price. The density of the solution of chloride of calcium should be 1.191 or
twenty three degrees Beaumè. At this degree of concentration the solution of
chloride of calcium presents the least resistance to the passage of the electric
current its specific resistance in this condition at a temperature of thirty degrees
centigrade being 4.6 ohms.
One of the chief advantages of this process is that it enables the most delicate
textile materials to be bleached without injuring the fibre. The electrolysed
solution of chloride of magnesium possessing great decolourizing power acts oven
when it contains a relatively small quantity of these chlorine compounds and as
the production of these chlorine compounds can be absolutely controlled or regulated
as required by adjusting the electric current the bleaching action is perfectly under
control.
Having now particularly described and ascertained the nature of the said
Invention and in what manner the same is to be performed I declare that what
I claim is
First. The employment in apparatus for bleaching by electrolysis of platinum
electrodes arranged and connected substantially as hereinbefore described and
illustrated in the accompanying drawings.
Second. The employment for bleaching purposes in general of the reactions
produced by the electrical decomposition of the salts or bleaching agents herein-
before specified the said salts or bleaching agents admitting of continual regeneration
substantially as herein before described.
Third. The several methods and combinations of apparatus for bleaching paper
pulp substantially as herein before described.