IMPROVEMENTS IN THE MANUFACTURE OF CHLORINE AND BLEACHING POWDER, CARBONATE OF SODA AND SODA ASH, AND SULPHATE OF IRON
Year: 1863

page_text: Street
Glasgow, in the County of Lanark, North Britain, Civil Engineer,
for the Invention of "IMPROVEMENTS IN THE MANUFACTURE OF CHLORINE
AND BLEACHING POWDER, CARBONATE OF SODA AND SODA ASH, AND SULPHATE
OF IRON." A Communication from abroad by Thomas Macfarlane,
Metallurgical Chemist, of Acton Vale, in the County of Bagot, and
Province of Canada.
LETTERS PATENT to William Johnson, of 166, Buchanan
Sealed the 30th June 1863, and dated the 14th January 1863.
PROVISIONAL SPECIFICATION left by the said William Johnson at
the Office of the Commissioners of Patents, with his Petition, on the
14th January 1863.
1, WILLIAM JOHNSON, of 166, Buchanan Street, Glasgow, in the County
of Lanark, North Britain, Civil Engineer, do hereby declare the nature of
the said Invention for "IMPROVEMENTS IN THE MANUFACTURE OF CHLORINE AND
BLEACHING POWDER, CARBONATE OF SODA AND SODA ASH, AND SULPHATE OF IRON,"
a communication from abroad by Thomas Macfarlane, Metallurgical
Chemist, of Acton Vale, in the County of Bagot, and Province of Canada,
to be as follows:-
This Invention has for its object certain improvements in the manu-
facture of chlorine and bleaching powder, carbonate of soda, soda ash,
and sulphate of iron.
In carrying out the combined processes by which the desired results

page_text: are obtained I proceed as follows:-Firstly, I take common crystallized
green vitriol or sulphate of iron, and heat the same until it loses it
water of crystallisation, and becomes more or less oxidized without losing
any sulphuric acid. I reduce the calcined green vitriol thus obtained
to fine powder, and mix it in the proportion of say, six hundredweight
of vitriol with four and a half hundredweight of common salt, (previously
heated until it no longer decrepitates), and one a half hundredweight
of peroxide of iron. These ingredients in fine powder being intimately
incorporated with each other 1 introduce them into a muffle calcining
furnace heated from below or in any convenient manner. That part of
the furnace over the hearth, which may be called the muffle, and to
which the flame or products of combustion of the fuel have no access is
connected with an exhausting machine which draws a current of air
through quicklime contained in a suitable chamber and over the mixture
which is spread out on the hearth of the muffle calciner. Double decom-
position takes place at a very low temperature betwixt the calcined
green vitriol and the common salt sulphate of soda resulting on the one
hand and protochloride and perchloride of iron on the other. The
temperature in the muffle is so low that neither of the chlorides of iron
are sublimed, but on the other hand the oxygen contained in the dry air
passing over the mixture decomposes both into peroxide of iron which
remains and chlorine gas which is drawn off by the exhausting machine.
It is of the utmost importance in this operation that the temperature
be kept at a low red heat, because, as is well known, that calcined green
vitriol and common salt at a higher temperature fuse and emit fumes
of perchloride of iron. In order to produce pure chlorine, the mixture
must not be allowed to fuse or even to sinter. During the operation
the materials are frequently stirred, and this also prevents sintering.
The raking door must always be kept closed excepting when the mixture
is being stirred, and the exhausting machine above mentioned must, of
course, be kept in motion during the whole operation. The chlorine is
drawn by the exhausting apparatus through an opening leading from
the muffle and through an iron or other suitable pipe joining the opening
and leading to two purifiers. The purifiers are wooden boxes lined with
lead, and furnished with lids having water joints. They are also
supplied with perforated bottoms, upon which rests a layer of coke about
four feet thick. This coke is, during the operation kept moist by water
falling on to a perforated shelf which distributes it over the surface of
the coke through which it percolates, and finally is run off at the bottom.
Pipes lead from the purifiers into a pair of absorbing boxes, cach of
which contains tiers of wooden or other trays or drawers with perforated
bottoms and filled with slaked lime for absorbing the chlorine. From

page_text: these boxes pipes lead into another pair of absorbing boxes connected
by pipes with the exhausting machine, which consists of a series of
cylinders containing smaller cylinders, the latter communicating with
the pipe from the absorbing boxes. The space betwixt the inner and
outer cylinders is partially filled with water in which moveable cylinders
rise and fall. These cylinders are set in motion by a driving shaft,
cranks, and connecting rods. When the cylinders rise certain valves
on their surfaces close and other valves on the inner cylinders open;
when they descend the reverse action takes place, and the air is forced
out of the moveable cylinders into the outer ones or cases, from which
it escapes by exit pipes. The chlorine produced in the muffle of the
furnace, in the manner above described is first drawn through the coke
in the purifier, where it comes in contact with the water, which absorbs
any traces of muriatic acid gas which it may contain. It then passes
over the lime contained in the drawers of one of the first pair of absorb-
ing boxes, where most of it is absorbed by the lime, bleaching powder
being formed; any portion of chlorine which may remain free after the
passage through this box is absorbed by the slaked lime in the drawers
of one of the second pair of absorbing boxes, the gas being in this case
drawn through holes in the bottom of the drawers and up through the
lime contained in them, every trace of chlorine contained in it is
absorbed, and then passes through the exhausting machine and out by
the exit pipes, only the constituents of the atmosphere which entered
the furnace in so far as they have not been absorbed by the materials
calcined in the muffle. As soon as the mixture in the furnace no longer
evolves chlorine, the exhausting machine is stopped, and the contents
of the furnace are drawn into a receptacle beneath. This residue con-
sists of about 600 lbs. of sulphate of soda and 500 lbs. of peroxide of iron;
provided the proportions above mentioned have been used. A fresh
quantity of the mixture is then introduced into the muffle, calciner, or
furnace, and the products drawn through the other purifier and absorb-
ing boxes. While the one set of absorbing boxes are in use, the other
set is opened, and the drawers containing the bleaching powder in the
first box removed and replaced by those of the second box, the lime in
which is only partially charged with chlorine. The second box is then
filled with drawers containing fresh lime, and the whole is again ready
for exposure to the current of chlorine from the furnace. The produc-
tion of chlorine and bleaching powder and of the residual mixture of
sulphate of soda and peroxide of iron constitutes the first part of this
Invention.
I next take the mixture of sulphate of soda and peroxide of iron
resulting as above described, and weighing about 1100 lbs., and mix

page_text: the same with about 214 lbs. of powdered coal or charcoal; then smelt
the mixture in a reverberatory smelting furnace, but before it is heated
up the hearth is prepared in the following manner:-100 parts of quick-
lime ground to powder are mixed with 16 parts of basic slag, such as is
commonly produced in copper smelting works, or of any other slag or
glass not too difficult of fusion. This mixture is beat into the bottom of
the furnace when in a dry state, and the depression for the hearth
scooped out in it, and the tap hole formed through it at the bottom,
as is customary in preparing the hearths of furnaces intended for smelt-
ing; the furnace is then gradually heated up and a strong heat continued
until the materials of the hearth slightly cake together; as soon as this
takes place a mixture of about100 parts of sulphate of soda and about 25
parts of powdered coal or charcoal is introduced; this soon fuses and is
totally absorbed by the hearth; more of the same mixture is then intro-
duced, and the introduction thereof is continued until no more of the
resulting suphuret of sodium is absorbed by the hearth. The furnace is
then kept at a red heat, and is ready to receive the mixture of sulphate
of soda, peroxide of iron, and charcoal or coal already referred to; very
soon after its introduction this mixture begins to fuse and emits jets of
yellow flame; after it has been properly stirred up, it enters into quiet
fusion, and is let off at the tap hole and run into iron moulds, in which
it solidifies in large blocks; it is totally without corroding action on the
hearth, and an almost unlimited number of charges may be smelted
down in it without the hearths being much affected, on the contrary,
it becomes and remains hard and compact, and can only with difficulty
be removed from the furnace. These blocks of smelted material which
contain sulphur, sodium, and iron, are immediately broken up and intro-
duced into water contained in a boiler or vessel, similar to that used for
evaporating alkaline solutions in the ordinary method of manufacturing
soda, and in which the flame and products of combustion pass over the
surface of the solution. On the introduction of the smelted material
into the water it is partially dissolved, and the solution assumes a deep.
greenish black colour from dissolved sulphuret of iron. When, however,
heat is applied to the solution, and the flame as well as the carbonic acid
produced in the combustion of the fuel is passed over it, the latter gas
is absorbed, the solution gradually becomes decolorised, and consists
almost solely of a solution of carbonate of soda. In the event of the
solutions becoming too much evaporated before the decolorisation is
effected more water is added, and the heating and exposure to the
products of combustion continued; during this operation the insoluble
sulphuret of iron remains at the bottom of the boiler or vessel. When
the supernatant solution has become colorless the fire in the grate is

page_text: slackened, and the contents of the boiler allowed to settle. The clear
liquid is then drawn off through a pipe, and fresh water introduced
among the insoluble sulphuret of iron; if this solution also becomes
green, it is decolorised in the same manner as the first solution. The
second solution is drawn off in the same manner.as the first, and the
same operation repeated with fresh water until the latter dissolves no
more soda from the sulphuret or iron. The first and more concentrated
solutions thus obtained are evaporated, and allowed to crystallise, when
carbonate of, soda in crystals separates the mother liquor from which
may be evaporated to dryness for the production of soda ash. The
weaker solutions obtained latterly from the sulphuret are used for treat-
ing fresh quantities of smelted material from the furnace. The sulphuret
of iron which remains after having been thus repeatedly treated with
water, is run off through a pipe in the bottom of the boiler into a box
fitted with a perforated bottom, over which a coarse cloth. is spread, it
here becomes drained of the water it contains, and on being removed
from the box is ready for being treated in the manner yet to be described.
The production of carbonate of soda and of insoluble sulphuret of iron in
the manner above described constitutes the second part of this Invention.
I expose the insoluble sulphuret of iron obtained, as above described,
and which is still in a moist state in considerable quantities, but with
as much surface exposed as possible to the action of the atmosphere and
of moisture. It may be exposed on a perforated wooden floor covered
with coarse cloth, which floor is supported over an impervious bottom
of clay or other material, so inclined and arranged that the solution
obtained in lixiviating the mass may be conveniently collected for further
treatment. The moist sulphuret rapidly oxidizes, and passing though
various intermediate stages of oxidation, it ultimately becomes very rich
in sulphate of iron; it must never be allowed to oxidize so rapidly as to
enter into combustion, because in that case sulphurous acid is produced
which would escape as gas, and be lost; this tendency to oxidize too
rapidly may be counteracted by keeping the mass moist. When a
sufficient quantity of sulphate of iron has been formed in the mass, hot
water is poured over its whole surface, which percolating through it
dissolves the sulphate, and falling on the impervious floor beneath is
gathered up in canals prepared for it, and finally collected in a large
reservoir. The solution thus obtained is concentrated in boilers of the
same description as those used for a similar purpose in copperas works
and crystals of green vitriol obtained in the manner usually adopted in
the same establishments. The exposure and lixiviation of the sulphurets
is continued and repeated until a residue is left consisting of peroxide
of iron, and containing little or no sulphur. The green vitriol obtained

page_text: as above described is used in the first part of this Invention, and the
residue of peroxide of iron if sufficiently pure may also be used in that
operation. The production of sulphate of iron in the manner above
described from the sulphuret of iron resulting in the former process, con-
stitutes the third and last part of this Invention.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said William Johnson in the Great Seal Patent Office on the
14th July 1863.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, WILLIAM
JOHNSON, of 166, Buchanan Street, Glasgow, in the County of Lanark,
North Britain, Civil Engineer, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Fourteenth day of January, in the year of our
Lord One thousand eight hundred and sixty-three, in the twenty-sixth
year of Her reign, did, for Herself, Her heirs and successors, give and
grant unto me, the said William Johnson, Her special license, that I,
the said William Johnson, my executors, administrators, and assigns, or
such others as I, the said William Johnson, my executors, administrators,
or assigns, should at any time agree with, and no others, from time to
time and at all times thereafter during the term therein expressed;
should and lawfully might make, use, exercise, and vend, within the
United Kingdom of Great Britain and Ireland, the Channel Islands, and
Isle of Man, an Invention for "IMPROVEMENTS IN THE MANUFACTURE OF
CHLORINE AND BLEACHING POWDER, CARBONATE OF SODA, AND SODA ASH, AND
SULPHATE OF IRON," a communication from abroad by Thomas Macfarlane,
Metallurgical Chemist, of Acton Vale, in the County of Bagot, and
Province of Canada, upon the condition (amongst others) that I, the
said William Johnson, my executors or administrators, by an intrument
in writing under my hand and seal, or under the hand and seal of one of
them, should particularly describe and ascertain the nature of the said
Invention, and in what manner the same was to be performed, and cause
the same to be filed in the Great Seal Patent Office within six calendar
months next and immediately after the date of the said Letters Patent.
NOW KNOW YE, that I, the said William Johnson, do hereby declare
the nature of my said Invention, and in what manner the same is to be
performed, to be particularly described and ascertained in and by the
following statement, reference being had to the accompanying Draw-
ings, and to the letters and figures marked thereon, that is to say:

page_text: This Invention has for its object certain improvements in the manu-
facture of chlorine and bleaching powder, carbonate of soda, soda ash,
and sulphate of iron.
In carrying out the combined process by which the desired results are
obtained I proceed as follows:-I take common crystallized green vitriol
or sulphate of iron obtained either by the ordinary methods, or in the
manner herein-after to be described, and heat the same until it loses
its water of crystallization and becomes more or less oxidized without
losing any pulphuric acid. I reduce the calcined green vitriol thus
obtained to fine powder and mix it in the proportion, of say, six hundred-
weight of vitriol with four and a half hundredweight of common salt
(previously heated until it no longer decrepitates), and one and a half
hundredweight of peroxide of iron which may readily be obtained by
calcining pure iron pyrites with five per cent. of common salt, and lixi-
viating the result, or by any of the usual methods. These ingredients
in a state of fine power being intimately incorporated with each other
I introduce them into a muffle calcining furnace, of any convenient and
suitable form, but the one illustrated by the Drawings hereunto annexed
is preferred.
Figure 1 is a side elevation of this furnace; Figure 2 is a longitudinal
section of the same in connection with the purifiers, absorbing boxes, and
exhausters herein-after referred to; Figure 3 is a horizontal section of the
entire apparatus; Figure 4 is an end elevation of the furnace; Figure 5
is a transverse section along the line 1, 2, and Figure 6 is a similar
section along the line 3, 4. The same letters of reference indicate corrc-
sponding parts throughout all these Figures.
A is the opening in the roof of the furnace through which the materials
to be calcined are introduced; B is the opening in the back wall of the
furnace through which the gaseous products of calcination are drawn off.
This opening is supplied with a damper C; D, D, are the flues through
which the flame from the grate E (into which the fuel is introduced from
both sides of the furnace) is conducted under the hearth of the furnace.
These flues stand in connection with the flues F, F, and chimney G,
through which the smoke escapes. The chimney is supplied with the
damper H; I is a door to the flues F, in order that the same as well as
the flues D may be cleaned. The grate E is in communication with the
flues D, through the flame holes L; M is a slit in the end wall of the
furnace nearest the working side, which serves, to receive the calcined
product on its being withdrawn from the furnace, and to carry it into
the receptacle N beneath. The slit is furnished with the damper O;
P is another slit in the sane wall supplied with a grating Q, and con-
stantly kept filled with quicklime or other hygrometric substance which

page_text: as it falls through the grating is removed through the opening R in the
outer wall on the working side; S is an iron roller on which a rake for
stirring the mixture is laid and worked; T is the calcining hearth which
rises a little towards the back wall U. It consists of a double layer of
fire-clay slabs or tiles two inches thick. The tiles of the lower layer are
furnished with a check so that they can be accurately fitted into each.
other. Upon this the second layer of tiles which do not require to be
checked is laid. The tiles of both layers must be brought as close to
each other as possible, and the joints carefully filled with fire-clay; V is.
an opening through which the furnace is worked, furnished with the
door W; X is the ash-pit, and, Y, the muffle or space betwixt the.hearth
and the roof. The mixture above mentioned is introduced through the
opening A, and falls on the hearth of the furnace previously. heated* to
faint redness by the fire on the grate E. By means of a rake introduced.
at and worked through the opening V, it is spread over the hearth, after
which the rake is withdrawn and the opening closed by lowering the
door W. That part of the furnace over the hearth. which may be called
the muffle, and to which the flame or products of combustion of the fuel
have no access is connected with an exhausting machine which draws a
current of air through the quicklime contained in the slit P, and over
the mixture which is spread out on the hearth of the furnace. Double
decomposition takes place at a very low temperature betwixt the calcined
green vitriol and the salt sulphate of soda resulting on the one hand and
protochloride and perchloride of iron on the other. The temperature in
the muffle is so low that neither of the chlorides of iron are sublimed, but
on the other hand the oxygen contained in the dry air passing over the
mixture decomposes both into peroxide of.iron which remains, and into
chlorine gas which is drawn off by any suitable exhausting machine. It
is of the utmost importance in this operation that the temperature be
kept at a low red heat because as is well known calcined green vitriol
and common salt ignited together at a higher temperature fuse and emit
fumes of perchloride of iron. In order to produce pure chlorine the
mixture must not be allowed to fuse or even to sinter. The peroxide of
iron used as one of the ingredients has some influence in preventing
sintering and eliminating the chlorine. The greater the quantity of
peroxide of iron used the more easy it is to calcine the mixture without
permitting it to cake together. I have not however found it necessary
to use more of it than the proportion above stated when the calcination
is performed with proper care. During the operation the-materials are
quietly but frequently stirred with a rake, and this also prevents sinter-
ing. The raking door must always be kept closed, excepting when the

page_text: mixture is being stirred and the exhausting machine above mentioned
must of course be kept in motion during the whole operation.
1 shall now proceed to describe the arrangement and construction of.
purifiers, absorbing boxes, and exhausters, which it is preferred to use
in connection with the herein-before described furnace. a, in Figures
2 and 3, represents an iron pipe leading from the opening B in the back
wall of the furnace to two purifiers b, b', c, c'. These branches are
supplied with the stop cocks d, d', one of which only is kept open at a
time and the other shut. The purifiers b, b', are wooden boxes lined with
lead and furnished with lids having water joints. They are also supplied
with perforated bottoms e upon which rests a layer of coke about four
feet thick. This coke is during the operation kept moist by water which
is introduced at the cock f, falls on the perforated shelf g, which dis-
tributes it over the surface of the coke through which it percolates and
is finally run off at the cock h; i, i, are pipes leading from the purifiers
into aspair of absorbing boxes k, k', each of which contains four tiers
of wooden trays or drawers 1, with perforated bottoms, and filled with
slaked lime for absorbing. the chlorine. The drawers of which there
are two in each tier are a few inches shorter than the box in which they
are placed, and they are so situated that the current of chlorine passes
underneath round their ends and over them in the direction shown by
the arrows.
The boxes are furnished with doors m, m³, at the sides
which when opened fall down, and when closed are secured by means of
cramps; n and n' are pipes leading into another pair of absorbing boxes
These boxes are not so long as those marked k, k, and the
drawers fit closely into them. They are furnished with doors at the
sides in the same manner as the boxes k, k¹; o is an iron pipe leading from
the second pair of absorbing boxes into the exhausting machine. This
pipe is also provided with two stop cocks p, p'. The exhausting machine
consists of a series of three cylinders q, containing the smaller cylinders r,
which latter communicate with the aforesaid pipe o. The space betwixt
the inner and outer cylinders up to the levels, (shown by the red line)
is filled with water in which the three movable cylinders t move up and
down. These cylinders t are set in motion by the shaft u, crank o, and
connecting rods w. When the cylinders t rise, certain valves & on their
upper ends close, and other valves in the inner cylinders open. When
they descend the reverse action takes, and the air is forced of the movable
cylinders into the outer ones or cases q, from which it escapes by exit
pipes at y. The furnace being worked, the cylinders in motion, the stop
cocks and p¹ closed, and those marked d and p opened the current of
gas from the furnace is drawn through the apparatus in the direction
shown by the arrows. The chlorine produced in the muffle of the

page_text: furnace in the manner above described is first drawn through the coke
in the purifier b, where it comes in contact with the water which absorbs
any traces of muriatic acid gas which it may contain. It then passes
over the lime contained in the drawers 1, of the box k where the greater
portion of it is absorbed by the lime bleaching powder being formed.
Any portion of chlorine which may remain free after the passage through
the box, is absorbed by the slaked lime in the drawers of the box "..
The gas being in this case drawn through holes in the bottom of the
drawers and up through the line contained in them, every trace of
chlorine contained in it is absorbed, and there passes through the ex-
hausting machine and out at y, the constituents only of the atmosphere
which entered the furnace in so far as they have not been absorbed by
the materials calcined in the muffle. As soon as the mixture in the
furnace ceases to evolve chlorine which may be known by withdrawing
a portion at V, and smelling it, the exhausting machine is stopped, the
damper C is closed, the slide or door O withdrawn, and the contents of
the furnace raked into the slit M through which it falls into the recep-
tacle beneath. This residue consists of about six hundred pounds of
sulphate of soda, and five hundred pounds of peroxide of iron, provided
the proportions above mentioned have been used. A fresh quantity of
the mixture is then introduced into the furnace, the cocks and p¹
opened, and those marked d and p closed in order that the products from
the furnace may be drawn through the other purifier and absorbing
boxes. The damper C is then opened the exhausting machine set in
motion and the same process as that already described repeated. While
the one set of absorbing boxes are in use, the other set is opened and
the drawers containing the bleaching powder in the box k or k¹ removed.
and replaced by those of the box k" or ", the lime in which is only
partially charged with chlorine. The box " or k, is then refilled with
drawers containing fresh lime, and the whole is again ready for exposure
to the current of chlorine from the furnace. The twelve hundredweights
of the original mixture produce about six hundred pounds of bleaching
powder. The production of chlorine and bleaching powder, and of the
residual mixture of sulphate of soda and peroxide of iron constitute the
first part of this Invention.
I next take the mixture of sulphate of soda, and peroxide of iron re-
sulting as above described, and weighing about one thousand one
hundred pounds and mix the same with two hundred and fourteen pounds
of powdered coal or charcoal, I then smelt the mixture in a reverberatory
smelting furnace of any suitable construction, the one shewn in Figures
7, 8 and 9 of the Drawings being preferred. Figure 7 is a side elevation
of this furnace; Figure 8 is a longitudinal vertical section, and Figure 9;

page_text: ȧ sectional plan of the same. In these Figures A is the ash-pit; B, the
grate; C, the fire-bridge; D a hopper for containing the mixture to be
introduced through the opening E into the furnace; F is the cavity for
containing the smelted materials; G, the hearth; H, the tap hole; I, a
flue leading into the chimney K; L, the furnace door; M, a door re-
quired for manipulating the tap hole H, and N, an opening for working
the furnace. Before the furnace is heated up the hearth G is prepared
in the following manner:-One hundred parts of quicklime ground to
powder are mixed with sixteen parts of basic slag such as is commonly
produced in copper smelting works, or of any other slag or glass not
too difficult of fusion. This mixture is well beaten into the bottom of
the furnace when in a dry state and the depression F for the hearth
scooped out in it, and the tape hole H formed through it at the bottom
as is customary-in preparing the hearths of furnaces intended for smelt-
ing. The furnace is then gradually heated up and a strong heat con-
tinued until the materials of the hearth slightly cake together. As soon
as this takes place a mixture of one hundred parts of sulphate of soda;
and twenty-five parts of powered coal or charcoal is introduced; this soon
fuses and is totally absorbed by the hearth; more of the same mixture is
then introduced, and the introduction thereof is continued until no more
of the resulting sulphuret of sodium is absorbed by the hearth. The
furnace is then kept at a red heat and is ready to receive the mixture
of sulphate of soda, peroxide of iron, and charcoal or coal already re-
ferred to. For the furnace above described a charge consists of about
forty hundredweights of the mixture. Very soon after its introduction
it begins to fuse and emits jets of yellow flame. After it has been
properly stirred up it enters into quiet fusion, and is let off at the tap
hole H, and run into iron moulds in which it solidifies in large blocks.
It is totally without corroding action on the hearth, and an almost un-
limited number of charges may be smelted down in it without the hearths
being much affected. On the contrary it becomes and remains hard
and compact and can only with difficulty be removed from the furnace.
These blocks of smelted material which contain sulphur, sodium, and
iron are immediately broken up and introduced into a boiler similar to
that used for evaporating alkaline solutions in the ordinary method of
manufacturing soda, and in which the flame and products of combustion
pass over the surface of the solution. Figures 10, 11, and 12 of the
Drawings represent respectively a transverse, longitudinal, and hori-
zontal section of this boiler and its furnace.
A is the ash-pit; B, the grate; C, the furnace door; D, the fire-bridge;
E, a slit in the fire-wall to prevent the heat from affecting the lenden
pan F which is covered with the brick lining G; H is a space occupied

page_text: by the solution and residue; I is an opening for introducing the smelted
blocks and water; K is a flue leading into the chimney L; M is the
working door; N, a box for receiving insoluble residue from the furnace;
O, a perforated bottom in the same; P, a pipe for leading off alkaline
solution; Q, a pipe for leading off insoluble residue; R, the level to
which the solution may rise in the space H. On the introduction of the
smelted material into the water it is partially dissolved and the solution
assumes a deep greenish black color from dissolved sulphuret of iron.
When however heat is applied to the solution, and the flame as well
as the carbonic acid produced by the combustion of the fuel is passed
over it, the latter gas is absorbed, the solution gradually becomes de-
colorised and consists almost solely of a solution of carbonate of soda. In
the event of the solutions becoming too much evaporated before the
decolorisation is effected, more water is added, and the heating and expo-
sure to the products of combustion continued. During this operation
the insoluble sulphuret of iron remains at the bottom of the boiler. or
vessel. When the supernatant solution has become colorless the fire in
the grate is slackened and the contents of the boiler allowed to settle.
The clear liquid is then drawn off through the pipe P and fresh water
introduced among the insoluble sulphuret of iron. If this solution also
becomes green it is discolorised in the same manner as the first solution.
The second solution is drawn off in the same manner as the first, and
the same operation repeated with fresh water until the latter dissolves
no more soda from the sulphuret of iron. The first and more concen-
trated solutions thus obtained are evaporated and allowed to crystallize
when carbonate of soda in crystals separates the mother liquor from
which may be evaporated to dryness in order to produce soda ash. The
weaker solutions obtained laterally from the sulphuret are used for
treating fresh quantities of smelted material from the furnace. The
sulphuret of iron which remains after having been thus repeatedly
treated with water is run off through the pipe Q into the box or recep-
tacle N over the perforated bottom O, over which a coarse cloth is
spread. It here becomes drained of the water it contains, and on
being removed from the box is ready for being treated in the manner
yet to be described. The production of carbonate of soda and of insoluble
sulphuret of iron in the manner above described constitutes the second
part of this Invention.
The insoluble sulphuret of iron obtained as above described and which
is still in a moist state is exposed in considerable quantities, but with
as much surface exposed as possible to the action of the atmosphere and
of moisture, It is laid on a perforated wooden floor covered with coarse

page_text: cloth, which floor is supported over an impervious bottom of clay or
other material so inclined and arranged that the solution obtained in
lixiviating the mass may be conveniently collected for further treatment.
The moist sulphuret rapidly oxidizes, and passing through various inter-
mediate stages of oxidation it ultimately becomes very rich in sulphate
of iron; it must never be allowed to oxidize so rapidly as to enter into
combustion because in that case sulphurous acid is produced which
would escape as gas and be lost; this tendency to oxidize too rapidly
may be counteracted by keeping the mass moist. When a sufficient
quantity of sulphate of iron has been formed in the mass hot water is
poured over its entire surface, which percolating through it dissolves
the sulphate and falling on the impervious floor beneath is collected in
canals prepared for it, and finally run into a large reservoir. The solu-
tion thus obtained is concentrated in boilers of the same 'description
as those used for a similar purpose in copperas works, and crystals of
green vitriol are obtained in the manner usually adopted in the same
establishments. The exposure and lixiviation of the sulphurets is con-
tinued and repeated until a residue is left consisting of peroxide of iron
and containing little or no sulphur. The green vitriol obtained as above
described is used in the first part of this Invention, and the residue of
peroxide of iron if sufficiently pure may also be used in that operation.
The production of sulphate of iron in the manner above described from
the sulphuret of iron resulting in the former process constitutes the third
and last part of this Invention.
Having described the nature of this Invention, I proceed to advert to
the advantages which it possesses over the ordinary methods for pro-
ducing bleaching powder and soda. These as at present pursued com-
prise the following processes:-
First, the manufacture of sulphuric acid from iron pyrites or sulphur
by the action of nitrous acid on the sulphurous acid and oxygen of the
atmosphere admitted into the leaden chamber, which nitrous acid is
produced by the action of sulphuric acid or nitrate of soda.
Second, the production of muriatic acid and sulphate of soda by the
action of sulphuric acid on common salt.
Third, the production of chlorine (and of bleaching powder by com-
bining the chlorine with lime) by the action of muriatic acid on peroxide
of manganese in which process however only one half of the chlorine
contained in the muriatic acid is evolved as gas, the other half com-
bining with manganese and forming therewith a waste product.
Fourth, the decomposition of sulphate of soda by igniting it with
limestone and charcoal, in which operation the sulphur combines with
lime or calcium and forms therein a waste product.

page_text: Mi Fifth, the extraction of carbonate of soda and soda ash from the pro-
duct of this ignition.
With regard to these, the ordinary processes, the following facts are
"observable:
First, the whole of the sulphur contained in the sulphuric acid and
one half of the chlorine contained in the common salt originally used are
"lost.
**
Second, they comprise five distinct processes, some of which, such as
the manufacture of sulphuric acid require very expensive apparatus.
Third, nitrous acid, peroxide of manganese, and limestone are used
"in these processes in such a manner as not to be recoverable or only with
"great expense and difficulty.
In comparing these processes with the present Invention it will be
observed.
First, that by means of the latter the sulphur contained in the sul-
phuric acid of the green vitriol used in the first operation is recovered
"and may be used an indefinite number of times and that the whole of
'the chlorine contained in the common salt is evolved as gas, and ren-
dered available for the manufacture of bleaching powder.
Second, that this Invention comprises only four operations, that is
one less than by the ordinary methods, and that these do not require
any extraordinarity expensive apparatus.
Third, that nitrous acid, peroxide of manganese, and limestone are
altogether dispensed with, only one material, peroxide of iron, being
used to replace the limestone, but always in such a manner as to be re-
covered and used again.
I am aware that it has been proposed to manufacture carbonate of
soda and soda ash by mixing together and igniting sulphate of soda;
"peroxide of iron and charcoal, or coal, exposing the resulting product
'to a stream of carbonic acid, and thereafter dissolving out the alkaline
matters with water, and I wish it to be understood that I do not claim
this method of manufacturing carbonate of soda, or soda ash when the
same is used alone or in combination with processes other than those
herein described, but what I claim as the Invention secured to me by
the herein-before in part recited Letters Patent is,―
First, the production of chlorine by heating a mixture of calcined
green vitriol, common salt, and peroxide of iron in a current of air in
the manner above described, and the use of the chlorine so produced
in any process in which gaseous chlorine may be advantageously applied.
Second; the application and use of the residue resulting from the pro-
duction of chlorine as above described to and in the manufacture of car-
bonate of soda and soda ash.

page_text: Third, the use of the refractory mixture of burnt lime and slag herein-
before described for forming the hearths of the furnaces employed in
smelting the mixture of sulphate of soda, peroxide of iron, and char-
coal, or coal, above-mentioned.
Fourth, the method of decolorising the deep greenish colored alkaline
solution in the above described manufacture of carbonate of soda and
soda ash as herein-before described.
Fifth, the production of sulphate of iron from the artificial sulphuret
of iron in the manner herein-before described.
Sixth, the combination of the peculiar process herein-before described
for manufacturing carbonate of soda and soda ash with the two other
parts of the Invention, the great advantages of this Invention being
derived from working these processes in combination with each other.
In witness whereof, I, the said William Johnson, have hereunto
set my hand and seal, this Tenth day of July, One thousand eight
hundred and sixty-three.
WILLIAM JOHNSON. (L.S.)