AN IMPROVED COMBINATION OF PROCESSES AND APPARATUS FOR THE MANUFACTURE OF SODA AND POTASH AND THE RECOVERY OF THE SULPHUR EMPLOYED THEREIN.
Year: 1876

page_text: LETTERS PATENT to Walter Weldon, of Abbey Lodge, Merton, in the County
of Surrey, for the Invention of "AN IMPROVED COMBINATION OF PROCESSES
AND APPARATUS FOR THE MANUFACTURE OF SODA AND POTASH AND THE
RECOVERY OF THE SULPHUR EMPLOYED THEREIN.'
"
PROVISIONAL SPECIFICATION left by the said Walter Weldon at the Office
of the Commissioners of Patents on the 28th August 1876
WALTER WELDON, of Abbey Lodge, Merton, in the County of Surrey. "AN
IMPROVED COMBINATION OF PROCESSES AND APPARATUS FOR THE MANUFACTURE
OF SODA AND POTASH AND THE RECOVERY OF THE SULPHUR EMPLOYED.THEREIN."
This Invention consists in a combination of methods, processes, and appliances,
whereby I am enabled to manufacture soda and potash without producing any
offensive residual product, and morcover, in such wise as to continually regenerate
and use again the most costly of the chemical agents or instruments employed in
that manufacture In what follows I shall speak only of the manufacture of soda,
but nearly all that will be said of it will be equally applicable also to the manų-
facture of potash.
The starting point of the said combination of methods and processes is sulphate
of soda, by what method produced I am not concerned. I convert this sulphate of
soda into sulphide of sodium by first heating the sulphate at least to fusion in a
suitable furnace, and then running it into a second furnace or other vessel con-
taining finely powdered coke or charcoal previously heated to redness, in which
second furnace or other vessel I thus de-oxidize the sulphate of soda, thereby
obtaining sulphide of sodium and carbonic acid gas. This deoxidation of the
sulphate of-soda is effected either solely or chiefly under the influence of the heat
communicated to the sulphate of soda on the one hand and to the coke on the other
before the two are mixed together, and so either entirely or for the most part
without application of heat to the mixture itself.
The object of this method of applying the heat necessary to enable the coke or
charcoal to deoxidize the sulphate of soda is to enable the deoxidation of the

page_text: sulphate of soda to take place in a furnace or vessel which shall have, while the
operation of deoxidation is going on, no opening excepting such as to permit of the
escape of the gaseous product of that operation By thus avoiding, either entirely or
for the most part, the presence of either air or products of combustion in the furnace
or vessel in which that operation is performed, I obtain both a very much purer
sulphide and a very much purer carbonic acid than have ever been obtained
hitherto by any similar reaction. When the sulphide so obtained is afterwards to
be converted into carbonate, I prefer that the said carbonic acid should pass from
the apparatus in which it and the sulphide are simultaneously produced into iron
gasometers, therein to be stored and cooled for subsequent application as will
herein-after be set forth; or the carbonic acid may be cooled and its heat utilized
on its way from the said apparatus to the gasometers.
The apparatus in which the sulphide of sodium and the carbonic acid aro
produced must be lined with either carbon or magnesia, to avoid such corrosion
by the sulphide as would rapidly destroy it while rendering the sulphide itself too
impure to permit of its economical conversion into soda.
When it is desired to convert the sulphide of sodium into caustic soda I treat
the sulphide by highly superheated steam, preferably, but not necessarily, in the
apparatus in which the sulphide was itself produced. The steam reacts upon the
sulphide of sodium in such wise as to produce two products, caustic soda and
.sulphuretted hydrogen. The latter passes off mixed with excess of steam
condense the steam out of the mixture and then treat the sulphuretted Lydrogen,
as will herein-after be described.
I
When the sulphide of sodium is to be converted into carbonate of soda the
sulphido must be run, in the fused state, from the furnace or vessel in which it was
produced into iron "bogies," lined with either carbon or magnesia and furnished
with covers to protect the sulphide from the an It can now either be dissolved
in water or allowed to cool, and then, when solid, broken into small lumfps.
If the sulphide is to be treated for its convcision into carbonate of soda by the
wet way I prefer to use a solution of the sulphide, containing from twelve to twenty
per cent. thereof, and to treat this solution by carbonic acid gas in the cold until
a certain precipitation of soda in the state of bicarbonate has been produced. I
then separate this precipitate of bicarbonate of soda from its mother liquor, and
employ the latter to dissolve more sulphide of sodium for another operation. The
bicarbonate of soda so obtained can either be sold as bicarbonate or its second
equivalent of carbonic acid can be driven off by heat, leaving a much purer soda
ash than has ever hitherto been manufactured When the bicarbonate is thus
treated for its conversion into soda ash, the carbonic acid driven off from it during
that operation must be collected for use again.
Instead of the solution of sulphide of sodium being treated by carbonic acid in
the cold, so as to produce bicarbonate, the two may be treated together hot, in
which case it will be sesqui-carbonate which will be produced But in this case
the resulting solution will have to be allowed to cool before the sesqui-carbonato
can be separated from the mother liquor. After cooling, the sesqui-carbonate can
be separated in the solid state, and on then being heated will give off half an
equivalent of carbonic acid and be converted into a pure soda ash.
By these methods merchantable soda is obtained from sulphide of sodium treated
by carbonic acid in the wet way, without the operation of evaporation. If,
however, the sulphide contains polysulphides, evaporation cannot be avoided,
because a precipitated carbonate of soda obtained from a solution of such a sulphide
would be inixed with free sulphur In such case it will be better to usc a solution
of sulphide, so dilute that when the sulphide has become completely converted into
carbonate the carbonate so produced shall remain wholly in solution The free
sulphur can then be allowed to settle, and the supernatant solution be then drawn
off from it and boiled down.
If it be preferred to treat the sulphide of sodium for its conversion into carbonate

page_text: of soda by the dry way the sulphide, in the state of small lumps, must be charged
into a series of gas-tight vessels communicating by pipes from the top of one to the
bottom of the next, and therein treated by carbonic acid and vapour of water in
the same methodical manner as will be described below for the treatment of solution
of sulphide by carbonic acid.
The sulphuretted hydrogen produced in any of the above-described methods of
decomposing sulphide of sodium I bring into intimate contact with a mixture with
water of finely divided oxide of either iron or manganese. There is thus produced
sulphide of iron or manganese in suspension in water. Into such mixture of
metallic sulphide with water I then inject air, so as to separate the sulphur in the
free state and reproduce the metallic oxide. I have now a mixture with water of
metallic oxide and free sulphur. I employ this to absorb more sulphuretted
hydrogen, and I then again treat the product by injection of air into it until the
metallic sulphide, which the second treatment with sulphuretted hydrogen had
reproduced, is again reconverted into oxide. These alternate treatments, first with
sulphuretted hydrogen and then with air, I repeat until the product is very rich in
sulphur. I then either separate such sulphur from the oxide with which it is
associated by dissolving out the latter by means of hydrochloric or other convenient
acid; or I employ the mixture itself, having first separated it from the water in
which it was suspended, and drained and dried it for the direct production of sul-
phurous acid, as will be well understood.
The above described combination of processes will enable the soda manufacture
to be carried on without production of any offensive residue, will enable the sulphur
employed therein to be continually recovered for use again, and will yield purer
products than can at present be obtained, excepting at such expense as can be borne
only in a few cases To carry out this method of manufacturing soda will require
apparatus as follows:-
Firstly Apparatus for the Manufacture of Sulphide of Sodium. This must
consist of a combination of a revolving furnace, lined with blocks or bricks of hardly
compacted carbon or hardly compacted magnesia with two other furnaces, one for
supplying the revolving furnace with products of combustion when such are
1equired therein, and the other for fusing and otherwise heating sulphate of soda.
The latter should preferably be a Siemens's regenerative furnace, and must be so
placed that fused sulphate of soda can be run from it at will into the revolving
furnace. It may also be so disposed as to be capable of supplying products of com-
bustion to the revolving furnace when necessary, thus avoiding the necessity of a
third furnace for that special purpose. The opening at that end of the revolving
furnace at which, when products of combustion are passed into and through such
furnace, the said products of combustion pass out of it, must be capable of being
connected at will with either of two conduits, one leading to a chimney through a
regenerator or otherwise to be used when products of combustion are being passed
into and through the furnace, and the other leading either to gasometers for storing,
or to apparatus for utilizing carbonic acid to be used when carbonic acid gas and
sulphide of sodium are being simultaneously produced therein. At the other end of
the revolving furnace the dispositions must be such that the annular disc suspended
between the revolving furnace and the furnace or combustion chamber which
supplies it with products of combustion and through the aperture in the centre of
which the said products of combustion enter, the revolving furnace may be moved
away at will, and a carbon disc without any aperture be readily attached to that
end of the furnace in such manner that when the furnace is in notion the carbon
dise shall move with it, keeping the opening at that end of the furnace completely
closed The revolving furnace can thus be converted at will either into a vessel
communicating at both ends with other apparatus, or into a vessel completely closed
at one end and communicating with other apparatus only at the other end These
dispositions will permit of powdered coke or charcoal being heated to redness in the
revolving furnace by means of products of combustion entering that furnace at one

page_text: end and passing out of it at the other end, and then passing on to a chimney, of
the supply of products of combustion to the revolving furnace being then cut off, of
the opening by which they had entered being then closed, and of the opening at the
other end of the revolving furnace being disconnected from the chimney and
connected with gasometers or other apparatus as aforesaid; of fused sulphate of
soda being then run in on to the red-hot coke or charcoal in the revolving furnace;
of the fused sulphate of soda and the hot coke being then rapidly mixed together
by the motion proper to the revolving furnace; and of reaction between them
being thus enabled to take place without access either of air or of products of
combustion, in a vessel having no opening except that necessary for the escape of 1
the resulting carbonic acid gas. If the sulphate of soda and the powdered coke
have been sufficiently heated separately before being thus mixed together in the
revolving furnace, reaction between them will go on to completeness without any
further application of heat. If they have not been sufficiently heated previously
when the reaction between them has gone on as far as it otherwise can com- 1
munication with the chimney must be re-established, and products of combustion
admitted for the few moments necessary to complete it.
Secondly. Apparatus for Decomposing the Sulphide of Sodium by Superheated
Steam. If the sulphide of sodium is to be decomposed by superheated steam, in
the same furnace as that in which it was itself produced, the said revolving furnace
must further be combined at one end with a Siemens-Cowper stove or other
apparatus for superheating steam, and at the other end with apparatus for absorbing
or otherwise treating sulphuretted hydrogen, the dispositions being such that the
revolving furnace may be connected therewith or disconnected therefrom at will.
If a special furnace be used for the treatment of the sulphide of sodium by highly 2
heated steam, such special furnace must be similarly connected with other apparatus
as just said.
An
Thirdly. Apparatus for Treating Sulphide of Sodium by Carbonic Acid.-For
treating solution of sulphide of sodium by carbonic acid gas it will be necessary to
employ a series of vessels which may conveniently be six in number, although their 3
number may be either greater or less than six. We will call them A, B, C, D, E,
and F. Each must be a "closed vessel furnished with an agitator capable when put
in motion after the vessel has been about half filled with solution of sulphide of
keeping the upper part of the vessel filled with a fine spray of such solution
arrangement of pipes passing from the upper part of one vessel to the upper part of the 3
next so connects all the vessels together, that a gas entering at the upper part of A can
pass through all the vessels of the series passing out at F, and there is a further dis-
position of pipes and cocks, such as to permit of the following mode of working:- Each
of the six vessels having been charged with enough solution of sulphide of to about half
fill it, the agitators are set in motion and a stream of carbonic acid gas is admitted into 4
the upper part of A. There it partially reacts upon and is partially absorbed by the
spray of solution of sulphide which it finds in the upper part of that vessel, so that
from the upper part of A to the upper part of B there passes a mixture of that
portion of the carbonic acid which has entered A, and has not been absorbed therein
with the sulphuretted hydrogen corresponding to such portion of the said carbonic
acid as has been absorbed in A. In B a portion of the carbonic acid in the said
mixture of gases reacts upon and is absorbed by sulphide of sodium, so that there
passes from B to C a mixture of carbonic acid and sulphuretted hydrogen containing
more sulphuretted hydrogen and less carbonic acid than were contained in the
mixture which passed into B from A. Absorption of carbonic acid and liberation 5
of sulphuretted hydrogen similarly go on in each successive vessel of the series,
until if the rate of admission of carbonic acid into A be properly regulated what
passes off from F is nearly or quite pure sulphuretted hydrogen. The admission
of carbonic acid into A, and the passage of the gas or gases through the six vessels
in the order A, B, C, D, E, F, is continued until the solution of sulphide in A is 5
completely decomposed, or until it has deposited the desired quantity of bicarbonate

page_text: r contains the required quantity of sesqui-carbonate. The contents of A are then
withdrawn and that vessel recharged, and the communications are ther so arranged
hat the carbonic acid now enters at B, the gases passing from B to C, from C to D,
rom D to E, from E to F, and from F to A, sulphuretted hydrogen passing off
from A. When the contents of B are at length withdrawn and that vessel
recharged the course of the gaseous current is again changed, the carbonic acid
being now made to enter at C, the current now passing through the six vessels in
the order C, D, E, F, A, B. From these examples the subsequent changes in the
course of the gases will be well understood.
When the solution of sulphide of sodium is treated by carbonic acid with the
object of obtaining not a precipitate of carbonate of soda but a solution thereof, the
carbonic acid may always enter at A, and sulphuretted hydrogen pass off at F,
the course of the gaseous current never varying from the order A, B, C, D, E, F.
In such case the six vessels should be connected together by a second set of pipes, in
such wise that solution of sulphide of sodium entering F from a suitable reservoir
which we may call G, shall first fill F to about half its depth, shall then flow over
into E and fill that vessel to the same depth as F, shall then similarly flow over
from E into D, and afterwards from D into C, fiom C into B, and from B into A,
until the solution of sulphide stands at the same height in all the six vessels
six vessels having thus been charged with solution of sulphide, the agitators put in
motion and carbonic acid made to enter at the upper part of A when the solution of
sulphide in A is completely converted into carbonate, the liquor pipe between A
and B is closed by means of a cock provided for that purpose, and the contents of
vessel A are drawn off. The cock between A and B, and at the same time the cock
between F and the reservoir G are then opened, so that more sulphide solution shall
flow in from G until the vessel A is refilled to the proper depth.
The
Of these two dispositions of apparatus for treating sulphide of sodium by carbonic
acid, the one first described most resembles that which should be employed when
the sulphide of sodium is treated in the dry way. For such treatment of sulphide of
sodium by carbonic acid in the dry way the first described disposition of apparatus
will need modifying only by the suppression of the agitators, and by making the
pipes for the gases pass from the upper part of one vessel to the bottom of the next,
instead of from the upper part of one vessel to the upper part of the next.
In each of the vessels used for treating solution of sulphide of sodium by carbonic
acid, I prefer that there should be several diaphragmns descending from the top of
the vessel to within a few inches of the surface of the solution in them when at
rest, the agitators being so disposed as to work between these diaphragms.
Fourthly. Apparatus for Treating the Sulphuretted Hydrogen.-The apparatus
for absorbing the sulphuretted hydrogen by means of oxide of iron or oxide of
manganese mixed with or suspended in water may be exactly the same as either
of the dispositions of apparatus above described for treating solution of sulphide of
sodium by carbonic acid To such apparatus must be added an "oxidizer," such as
is now universally used in my process for the regeneration of the peroxide of
manganese employed in the manufacture of chlorine, for the purpose of treating by
injection of air the mixture of metallic sulphide with water, which results from the
treatment by sulphuretted hydrogen of a mixture with water of one of the metallic
oxides aforesaid.
The dispositions of apparatus above set forth I believe to be the best for my
purpose, but some of them may be modified in various ways without departing
from the Invention the nature of which is above described. In my final Specifi-
cation the said dispositions of apparatus will be more particularly described, and
will be illustrated by such Drawings as may be necessary to their clear
comprehension.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Walter Weldon in the Great Seal Patent Office on the 26th February
1877.
AN
WALTER WELDON, of Abbey Lodge, Merton, in the County of Surrey
IMPROVED COMBINATION OF PROCESSES AND APPLIANCES FOR THE MANUFACTURE
or SODA AND POTASH AND THE RECOVERY OF THE SULPHUR EMPLOYED THEREIN."
This Invention consists in a combination of methods, processes, and appliances,
whereby I am enabled to manufacture soda and potash without producing any
offensive residual product, and, moreover, in such wise as to continually regenerate
and use again the most costly of the chemical agents or instruments employed in
that manufacture. In what follows I shall speak only of the manufacture of soda,
but nearly all that will be said of it will be equally applicable also to the manu-
facture of potash.
The starting point of the said combination of methods and processes is sulphate
of soda, by what method produced I am not concerned. I convert this sulphate of
soda into sulphide of sodium by first heating the sulphate at least to fusion in a
suitable furnace, and then running it into a second furnace or other vessel containing
finely powdered coke or charcoal previously heated to redness, in which second
furnace or other vessel 1 thus deoxidize the sulphate of soda, thereby obtaining
sulphide of sodium and carbonic acid gas This deoxidation of the sulphate of soda
is offected either solely or chiefly under the influence of the heat communicated to
the sulphate of soda on the one hand and to the coke on the other before the two
are mixed together, and so either entirely or for the most part without application
of heat to the mixture itself.
The object of this method of applying the heat necessary to enable the coke or
charcoal to deoxidize the sulphate of soda is to enable the deoxidation of the
sulphate of soda to take place in a furnace or vessel which shall have, while the
operation of deoxidation is going on, no opening excepting such as to permit of the
escape of the gaseous product of that operation By thus avoiding either entirely
or for the most part the presence of either air or products of combustion in the
furnace or vessel in which that operation is performed, I obtain both a very much
purer sulphide and a very much purer carbonic acid than have ever been obtained
hitherto by the reaction of carbonaceous matter upon sulphate of soda. When the
sulphide so obtamed is afterwards to be converted into carbonate, the said carbonic
acid should pass from the apparatus in which it and the sulphide are simultaneously
produced either into iron gas holders, therein to be stored and cooled for subsequent
application as will herein-after be set forth, or directly to apparatus in which it
may react on sulphide of sodium produced in a previous operation.
The apparatus in which the sulphide of sodium and carbonic acid are produced
must be lined with carbon to avoid such corrosion by the sulphide as would rapidly
destroy it, while rendering the sulphide itself too impure to permit of its economical
conversion into soda.
When it is desired to convert the sulphide of sodium into caustic soda I treat the
sulphide by highly superheated steain, preferably but not necessarily in the
apparatus in which the sulphide was itself produced. The steam reacts upon the
sulphide of sodium in such wise as to produce two products, caustic soda aud
sulphuretted hydrogen. The latter product I treat for the recovery of sulphur from
it as will herein-after be described.
When the sulphide of sodium is to be converted into carbonate of soda, the
sulphide must be run in the fused state from the furnace or vessel in which it was 5
produced into iron "bogies" lined with carbon and furnished with covers to protect
the sulphide from the air. In these it is conveyed to the vessels in which it is to
be dissolved, in order that it may be treated in the state of solution by carbonic acid
gas. To these vessels also there should be as little access of air as possible.

page_text: If the sulphide is to be treated for its conversion into carbonate of soda by the
wet way, I prefer to use a solution of the sulphide containing from twelve to twenty
per cent. thereof, and to treat this solution by carbonic acid gas in the cold until a
certain precipitation of soda in the state of bicarbonate has been produced. I then
separate this precipitate of bicarbonate of soda from its mother liquor and employ
the latter to dissolve more sulphide of sodium for another operation, first adding to
the mother liquor enough water to compensate for that removed as water of
combination with the bicarbonate. The bicarbonate of soda so obtained can
cither be used as bicarbonate, or its water and its second equivalent of carbonic
acid can be driven off from it by heat, leaving a much purer soda ash than has ever
hitherio been manufactured. When the bicarbonate is thus treated for its conversion
into soda ash, the carbonic acid duiven off from it during that operation should be
applied for the decomposition of more sulphide.
Instead of the solution of sulphide of sodium being treated by carbonic acid in the
cold so as to produce bicarbonate, it may be treated there with hot, in which case it
will be sesqui-carbonate of soda which will be produced. In this case the resulting
solution will have to be allowed to cool before solid sesqui-carbonate can be separated
from it After cooling much of the sesqui-carbonate can be separated as crystals, which
on being heated will give off water and half an equivalent of carbonic acid, and be
so converted into a pure soda ash The mother liquor from sesqui-carbonate thus
obtained must be re-employed in the same way as the mother liquor from bicarbonate
until it has become too highly charged with impurities.
By these methods, when the sulphide of sodium is practically pure monosulphide,
merchantable soda is obtained from sulphide of sodium treated by carbonic acid in
the wet way without the operation of evaporation. If however the sulphide
contains polysulphides evaporation cannot be avoided, because a precipitated car-
bonate of soda obtained from a solution of such a sulphide- would be mixed with
free sulphur. In such case it will be better to use a solution of sulphide so dilute .
that when the sulphide has become completely converted into carbonate the carbonate
so produced shall remain wholly in solution. The fiee sulphur can then be allowed
to settle, and the supernatant solution be then drawn off from it and boiled down.
In treating solution of sulphide of potassium by carbonic acid only a solution of
carbonate of potash can be obtained, the carbonates of potash being all too soluble
to permit of their being obtained as precipitates.
The sulphuretted hydrogen produced in treating sulphide of sodium by either
steam or carbonic acid, as above described, I bring into intimate contact with a
mixture with water of finely divided oxide of either iron or manganese. There
is thus produced sulphide of iron or manganese in suspension in water. Into such
mixture of metallic sulphide with water I then inject air, so as to separate the
sulphur in the free state, and reproduce the metallic oxide. I have now a mixture
with water of metallic oxide and free sulphur. I employ this to absorb more sul-
phuretted hydiogen, and I then again treat the product by injection of air into it,
until the metallic sulphide which the second treatment with sulphuretted hydrogen
had reproduced is again reconverted into oxide. These alternate treatments, first
with sulphuretted hydrogen, and then with air, I repeat until the product is very
rich in sulphur. I then either separate such sulphur from the oxide with which it
is associated by dissolving out the latter by means of hydrochloric or other con-
venient acid, or employ the mixture itself, having first separated it from the water
in which it was suspended, and drained and dried it for the direct production of
sulphurous acid, as will be well understood.
The above-described combination of processes will enable the soda manufacture
to be carried on without production of any offensive residue, will enable the sulphur
employed therein to be continually recovered for use again, and will yield purer
products than can at present be obtained, excepting at such expense as can be
borne only in a few cases. To carry out this method of manufacturing soda will
require apparatus as follows:-
Firstly. Apparatus for the Manufacture of Sulphide of Sodium.-This may consist

page_text: of a combination of a revolving furnace with two other furnaces, one for supplying
the revolving furnace with products of combustion when such are required therein,
and the other for fusing and otherwise heating sulphate of soda. The latter should
preferably be a Siemens's regenerative furnace, and it may be so disposed as to be
capable of supplying products of combustion to the revolving furnace, thus avoiding |
the necessity of a third furnace for that special purpose. The revolving furnace,
while otherwise resembling the revolving furnaces at present in nearly general use
among manufacturers of alkali, must be specially disposed as follows:-It must be
lined interiorly with blocks of agglomerated and hardly compressed coke to protect
it from corrosion by the sulphide to be produced in it; that end of it at which when
its contents are being heated products of combustion enter it must be capable of
being completely closed at will. To this end the annular disc, through the aperture
in the centre of which products of combustion pass into it when its contents are
being heated, must be suspended between it and the furnace, supplying the said
products of combustion in the same manner otherwise as in the case of ordinary
revolving furnaces, but so that it can swing like a pendulum, and can thus be
instantly drawn aside when required. Another disc must be provided and kept
ready, supported on edge on a suitable carriage, to be pushed forward to take the
place of the annular disc when required, this other disc being of solid carbon enclosed
in a stout iron hoop having a broad flange, in which flange are holes corresponding
to bolts projecting from the end of the revolving furnace. In this carbon disc there
is no aperture, and instead of being merely suspended between the revolving furnace
and the furnace supplying thereto products of combustion, in such wise as not quite
to touch either furnace, as is the case with the annular disc when such annular
disc is in use, this carbon disc when in use is attached to the revolving furnace
by means of the bolts aforesaid in such wise as to revolve with the furnace when
the furnace is in evolution, and it must fit so accurately as to completely close
in such case the aperture over which it is placed The aperture at the other ond
of the revolving furnace, by which when products of combustion are passing into
the revolving furnace they afterwards pass out of it, must communicate with a
flue or conduit which at some short distance from the revolving furnace shall
divide into two branches, one going to a chimney, and the other to apparatus for
either storing or directly utilizing carbonic acid, and in each of the said branches
there must be a valvo or damper so as to permit of the revolving furnace being made
to communicate with either the chimney or the said other apparatus at will
furnace for supplying products of combustion to the revolving furnace must be
so disposed that the said products of combustion can either be sent into the
revolving furnace, or be cut off therefrom and sent elsewhere at will.
The
The Siemens's furnace should be so placed and at such elevation that fused
sulphate of soda can run from it into the revolving furnace, the fused sulphate of
soda preferably entering the revolving furnace through the man-hole by which
ordinary revolving furnaces are charged and discharged.
For running out the fused sulphate of soda from the Siemens's furnace there
must be an opening in its side, which opening when not in use can be closed by a
sliding damper formed of a fire-brick tile, or by any other convenient appliance.
These dispositions will permit of powdered coke or charcoal being heated to redness
in the revolving furnace, by means of products of combustion entering that furnace
at one end and passing out of it at the other end, and then passing on to a
chimney, of the supply of products of combustion being then cut off, of the opening
by which they bad entered being then closed, and of the opening at the other end
of the revolving furnace being disconnected with the chimney and connected with
gas holders or other apparatus as aforesaid, of fused sulphate of soda being then
run in on to the red-hot coke or charcoal in the revolving furnace, of the fused
sulphate of soda and the hot coke being then rapidly mixed together by the motion
proper to the revolving furnace, and of the reaction between them being thus
enabled to take place, without access either of air or of products of combustion, in
a vessel having no opening for the time being, except that necessary for the escape

page_text: of the resulting carbonic acid gas. If the sulphate of soda and the powdered coke
have been sufficiently heated separately before being thus mixed together in the
revolving furnace, reaction between them will go on to completeness. without any
further application of heat. If they have not been sufficiently heated previously,
when the reaction between them has gone on as far as it otherwise can, commu-
nication with the chimney must be re-established, and products of combustion
admitted for such time as may be necessary to complete it.
When it is not required to utilize the gaseous product of the reaction for sub-
sequent conversion of the sulphide into carbonate, or otherwise, the revolving
furnace will of course always communicate with the chimney, instead of sometimes
with the chimney and sometimes with other apparatus, as above said.
The above described apparatus and method of working may be modified in in
various ways
Thus the furnace in which the sulphate of soda is heated to fusion
may be other than a Siemens's furnace; the furnace in which the previously fused
sulphate of soda is mixed with the previously heated coke or charcoal may be other
than a revolving furnace; the furnace in which the coke or charcoal is heated may
be other than that in which it afterwards reacts on the fused sulphate of soda; and
instead of the previously fused sulphate of soda being added to the previously
heated coke or charcoal, the previously heated coke or charcoal may be added to the
previously fused sulphate of soda.
Secondly. Apparatus for Decomposing the Sulphide of Sodium by Superheated
Steam If the sulphide of sodium is to be decomposed by superheated steam in
the same furnace as that in which it was itself produced, the said revolving
furnace must further be combined, at one end with a Siemens-Cowper stove or
other apparatus for superheating steam, and at the other end with apparatus for
absorbing or otherwise treating sulphuretted hydrogen, the dispositions being such
that tho revolving furnace may be connected therewith or disconnected therefrom
at will If a special furnace be used for the treatment of the sulphide by highly
heated steam such special furnace must be similarly connected with other apparatus,
as aforesaid.
The method of working consists simply in sending superheated steam into the
revolving furnace containing sulphide of sodium, which has either been produced
therein, or having been produced in other apparatus has been charged thereinto, as
long as sulphuretted hydrogen continues to be evolved.
Thirdly. Apparatus for Treating Sulphide of Sodium with Carbonic Acid.-For
treating solution of sulphide of sodium by carbonic acid gas it will be necessary
to employ a series of vessels, which may conveniently be six in number, although
their number may be either greater or less than six. We will call them A, B, C,
D, E, and F. Each must be a closed vessel, furnished with an agitator, capable
when put in motion after the vessel has been about half filled with solution of sul-
phide of maintaining in the upper part of the vessel a fine rain or spray of such
solution. An arrangement of pipes passing from the upper part of one vessel to the
upper part of the next so connects all the vessels together that a gas entering at
the upper part of A can traverse all the vessels of the series, and then pass out
at F, and there is a further disposition of pipes and cocks, such as to permit of the
following mode of working:
-
Each of the six vessels having been charged with enough solution of sulphide of
sodium to about half fill it, the agitators are set in motion, and a stream of carbonic
acid gas is admitted into the upper part of A; there a portion of it reacts upon the
solution of sulphide in that vessel, and so becomes absorbed with liberation of
sulphuretted hydrogen, which sulphuretted hydrogen mixed with what carbonic
acid has not been absorbed in A passes on from the upper part of A to the upper
part of B In B a portion of the carbonic acid in the said mixture of gases similarly
reacts and is absorbed, so that there passes from B into C a mixture of carbonio
acid and sulphuretted hydrogen containing more sulphuretted hydrogen and less
carbonic acid than were contained in the mixture which passed into B from A.
Absorption of carbonic acid and liberation of sulphuretted hydrogen similarly go on

page_text: in each successive vessel of the series, until, if the rate of admission of carbonic acid
into A be properly regulated, what passes off from F is nearly pure sulphuretted
hydrogen The admission of carbonic acid into A, and the passage of the gas or
gases through the six vessels in the order A, B, C, D, E, F, is continued until the
solution of sulphide in A is completely decomposed, or until it has deposited the
desired quantity of bicarbonate or contains the required quantity of sesqui-carbonate.
The contents of A are then withdrawn, and that vessel is recharged, and the com-
munications are then so arranged that the carbonic acid now enters at B, the gases
passing from B to C, from C to D, from D to E, from E to F, and from F to A,
sulphuretted hydrogen passing off from A. When the contents of B are at length
withdrawn and that vessel recharged, the course of the gaseous current is again
changed, the carbonic acid being now made to enter at C, the current now passing
through the six vessels in the order C, D, E, F, A, B. From these examples the
subsequent changes in the course of the gases will be well understood.
When the solution of sulphide of sodium is treated by carbonic acid with the
object of obtaining, not a precipitate of carbonate of soda, but a solution thereof, the
carbonic acid may always enter at A, and sulphuretted hydrogen pass off from F,
the course of the gaseous current never varying from the order A, B, C, D, E, F. In
such case the six vessels should be connected together by a second set of pipes in
such wise that solution of sulphide of sodium entering F from a suitable reservoir,
which we may call G, shall flow from F into E, from E into D, from D into C, from
C into B, and from B into A, until all the six vessels are about half filled with it.
The six vessels having thus been charged with solution of sulphide, the agitators
are put in motion, and carbonic acid made to enter at the upper part of A. When
the solution of sulphide in A is completely converted into carbonato, the liquor pipe
between A and B is closed by means of a stop-cock provided for that purpose, and
the contents of vessel A are drawn off. The cock between A and B, and at the
same time the cock between F and the reservoir G are then opened, so that more
sulphide solution shall flow in from G until the vessel A is refilled to the proper level.
In each of the vessels used for treating solution of sulphide of sodium by carbonic
acid, I prefer that there should be several diaphragms descending from the top of
the vessel to within a few inches of the surface of the solution in them when at rest,
the agitators being so disposed as to work between these diaphragms.
Fourthly. Apparatus for Treating the Sulphuretted Hydrogen.-The apparatus
for absorbing the sulphuretted hydrogen by means of oxide of iron or oxide of
manganese mixed with. or suspended in water, may consist of a similar series of
absorbers to those just described for treating solution of sulphide of sodium by
carbonic acid. To such apparatus must be added an "oxydizer," such as is now
universally used in my process for the regeneration of the peroxide of inanganese
employed in the manufacture of chlorine, for the purpose of treating by injection of
air the mixture of metallic sulphide with water which results from the treatment
by sulphuretted hydrogen of a mixture with water of one of the metallic oxides
aforesaid.
Having thus described the nature of my said Invention, and in what manner the
same is to be performed, I would have it understood that the processes and
appliances above described are separately the subject of other Patents, numbered
respectively 2008 of the year 1871, and 3380, 3383, 3387, 3388, and 3389, all of
the year 1876, but that I claim as the Invention to be secured to me by the herein-
before in part recited Letters Patent, the combination of processes and apparatus
for the manufacture of soda and potash, substantially as is above set forth.
In witness whereof, I have hereunto set my hand and seal, this Twenty-
fourth day of February, in the year of our Lord One thousand eight
hundred and seventy-seven.