IMPROVEMENTS IN THE MANUFACTURE OF SULPHIDE OF SODIUM AND SULPHIDE OF POTASSIUM, CONSISTING PARTLY IN A NEW METHOD OR PROCESS AND PARTLY IN MEANS AND APPLIANCES FOR CARRYING THE SAME INTO EFFECT
Year: 1876

page_text: LETTERS PATENT to Walter Weldon, of Abbey Lodge, Merton, in the County
of Surrey, for the Invention of "IMPROVEMENTS IN THE MANUFACTURE OF
SULPHIDE OF SODIUM AND SULPHIDE OF POTASSIUM, CONSISTING PARTLY IN A
NEW METHOD OR PROCESS AND PARTLY IN MEANS AND APPLIANCES FOR
CARRYING THE SAME INTO EFFECT."
Sealed the 24th November 1876, and dated the 28th August 1876.
PROVISIONAL SPECIFICATION left by the said Walter Weldon at the Office
of the Commissioners of Patents on the 28th August 1876.
"IM-
WALTER WELDON, of Abbey Lodge, Merton, in the County of Surrey.
PROVEMENTS IN THE MANUFACTURE OF SULPHIDE OF SODIUM AND SULPINDE of
POTASSIUM, CONSISTING PARTLY IN A NEW METHOD OR PROCESS AND PARTLY IN
MEANS AND APPLIANCES FOR CARRYING THE SAME INTO EFFECT."
It has been many times proposed, and although less frequently, it has been many
times attempted to manufacture soda by converting sulphate of soda into sulphide
of sodium and then decomposing such sulphide of sodium by carbonic acid. This
method of manufacturing soda would permit the utilization of the whole of the
sulphur contained in the sulphate of soda employed, and would moreover avoid the
production of the offensive residue known as "alkali waste." But all attempts to
practically apply this method have hitherto failed.
A principal cause of this failure has been the powerfully corrosive action of
sulphide of sodium upon the materials of which all furnaces or other appliances
for the manufacture of sulphide of sodiumn have hitherto been constructed.
The manufacture of sulphide of sodium has usually been attemped by beating to
a suitable temperature a mixture of sulphate of soda with coal, coke, or other form
of carbonaceous matter, and the furnaces or other apparatus employed have usually
been constructed either of brick or of cast iron Sulphide of sodium, however, at a
high temperature, attacks both those materials with extreme energy Hence when
only enough carbonaceous matter to decompose the sulphate of soda has been used,
the furnaces employed have become useless after a very few operations, and the
product obtained has been largely contaminated with compounds resulting from the
reaction of sulphide of sodium upon the materials of which the furnaces have been'
formed. When an excess of carbonaceous matter has been employed, the contact'
•

page_text: of the resulting sulphide of sodium with the material of the furnaces has been less
intimate, and the wear of the furnaces has consequently been less than in the other
case, but the wear of the furnaces has still been excessive, and although the product
has contained a smaller proportion of impurities due to corrosion of the furnaces or
other apparatus, it has contamed in addition a more or less considerable residue of
carbonaceous matter.
The furnaces or other apparatus in which it has hitherto been attempted to manu-
facture sulphide of sodium have thus worn out too rapidly to permit of the manu-
facture being continued, and the product obtained in such furnaces or other
apparatus has always been extremely impure.
Another principal cause of the said failure has lain in the methods by which in
all attempts to manufacture sulphide of sodium by the reaction upon sulphate of
soda of solid carbonaceous matter, the heat necessary to enable the carbonaceous
matter to react upon the sulphate of soda has been applied. Either the method of
working has been such that the sulphide of sodium has been formed in an atmo-
sphere of the products of combustion employed to heat the sulphate of soda and
the carbonaceous matter; these materials either mixed together, or the sulphate of
soda at one end of a furnace, and the carbonaceous matter at the other end of the
same furnace, being heated by direct contact with the said products of combustion,
or the sulphate of soda and the carbonaceous matter have been mixed together in
the cold, and the mixture then subjected to transmitted heat in a "blind" furnace
or muffle.
The first mentioned method of applying the necessary heat has two very serious
disadvantages, firstly, sulphide of sodium is an appreciably volatile body, and a
current of hot gases passing through the apparatus in which it is being manu-
factured carries off considerable quantities of it. The sulphide of sodium thus
carried off is not merely lost, but it attacks the bricks of the flues or other conduits
for the gases passing from the apparatus as in such wise to cause their rapid
destruction; secondly, whereas sulphide of sodium, in order to be capable of being
converted into merchantable soda in the most economical manner, must be practically
pure monosulphide, unmixed or nearly so with compounds containing more than
one equivalent of sulphur per equivalent of sodium When a mixture of sulphate
of soda and carbonaceous matter is heated by direct contact with products of com-
bustion, the steam and free oxygen in such products of combustion give rise to
reactions, which result in the production of considerable quantities of polysulphides
as well as of several other compounds other than monosulphide of sodium, while
by either method of heating, when the carbonaceous matter employed is coal and
not coke the hydrogen of the coal tends to the same result.
In the method of heating by transmitted heat a similar result is produced by the
air, which is admitted when the doors of the muffle furnace are opened to permit
of the charge being stirred. This presence of polysulphides in the product, and
that of the impurities due to corrosion of the furnaces, render solution and evapora-
tion by whatever method the sulphide be converted into carbonate absolutely
essential to the obtainment of a merchantable soda, whereas either both these
operations or at least the second, and by far the more costly of them, could be
avoided if the sulphide wore monosulphide and practically pure.
Another cause of the insuccess of all attempts made heretofore to practically
apply the method of manufacturing soda, to which reference has been made above,
has been the difficulty of obtaining a sufficiently pure carbonic acid wherewith,
after having produced sulphide of sodium, to convert it into merchantable soda.
Theoretically, when no excess of carbonaceous matter is employed, the gaseous
product of the reaction of carbonaceous matter upon sulphate of soda is this very
agent, carbonic acid, and it has often been proposed to employ for the conversion of
sulphide of sodium into carbonate of soda the carbonic acid so resulting from the
reaction by which the sulphide is itself formed, but the methods of heating
employed for the production of the sulphide have rendered the realization of this
method hitherto impossible. If carbonic acid.gas be much diluted with other,

page_text: although inert gases, its action is so enfeebled thereby that the quantity of it
required for the decomposition of sulphide of sodium becomes impracticably great,
while the treatment of sulphide of sodium by carbonic acid associated with
comparatively small quantities of free oxygen yields, instead of merchantable
carbonate of soda, a comparatively worthless mixture of carbonate with hypo-
sulphite and other salts. Hence, in all attempts made hitherto to manufacture
sulphide of sodium, it has been impossible to employ for the decomposition of the
sulphide the gaseous product of the reaction by which it was formed If the
sulphide were formed after the manner oftenest proposed in presence of an excess
of carbon that gaseous product was not carbonic acid at all, but carbonic oxide, and
when the said gaseous product has been really carbonic oxide it has always been
associated with free oxygen, and generally with large quantities of products of
combustion as well. And pure carbonic acid, as obtained by any means hitherto
known, has always been, and still is, much too costly for use for the manufacture
of soda by the decomposition of sulphide of sodium.
My present Invention consists in means of avoiding the causes above set forth
alike of the prohibitory cost and of the fatal impurity of sulphide of sodium as
hitherto obtained, of thus manufacturing sulphide of sodium economically, and of
such purity as to be practically a new product, capable of conversion into merchant-
able soda by simpler and cheaper means than any hitherto practicable, and than
any hitherto proposed, and of obtaining at the same time a gaseous product,
consisting of nearly pure and undiluted carbonic acid, perfectly available for the
subsequent conversion of the sulphide into carbonate.
The corrosion of the furnaces or other apparatus to be employed for the manu-
facture of sulphide of sodium I avoid by lining them with blocks of carbon. This
carbon lining nay he made of gas retort graphite, or of certain kinds of native
graphite, or, which will generally be the cheaper and more convenient plan,
of artificial blocks or bricks obtained by mixing powdered coke with gas tar,
submitting the mixture to powerful pressure in suitable moulds, and then
heating the blocks or bricks so obtained in such manner and under such
conditions that the tar in them shall undergo destructive distillation without the
blocks or bricks themselves either losing their shape or sensibly altering their
dimensions I prefer that such blocks or bricks should be so shapen as to be
capable of fitting into one another, and in fitting them together in the furnaces or
other apparatus to be lined with them I prefer to smear those surfaces of them
which are to come into mutual contact either with tar or with a mixture of tar and
powdered coke Instead of such carbon lining a lining of blocks or bricks of
hardly compacted magnesia may also be used.
The kind of furnace in which, when lined as aforesaid, I prefer to effect the
reaction of carbonaceous matter upon sulphate of soda is the kind which is known
to alkali makers as the "revolving furnace." In almost any other kind of furnace
the charge operated upon would have to be stirred from time to time with iron
tools, which tools would be rapidly eaten away by sulphide of sodium, much of
the said sulphide becoming thereby converted into double sulphide of sodium and
iron. The sulphide of sodium in such double sulphide could not be converted into
merchantable soda by any practicable means, and its presence with the remainder
of the sulphide of sodium would render essential to the conversion of the latter
into merchantable soda that operation of evaporation which this Invention will
enable me to avoid. In connection with a "revolving furnace" lined as aforesaid
I employ iron "bogies" similarly lined, and adapted with redily fixable covers to
receive the sulphide of sodium in cases in which its treatment for conversion
into merchantable products is not performed in the furnace in which it is
produced.
What is known to manufacturers of alkali as the "revolving furnace" is a long
cylinder, placed horizontally, arranged so as to be capable of revolving on its longer
axis, and having an opening at each end to permit of its contents being heated by
the passage through it of products of combustion. For the purposes of this Inven-

page_text: tion the revolving furnace must not only be so lined as to be rendered inattackable
. by fused sulphide of sodium which would completely destroy in a very short time
any revolving furnace at present in use, but it must also be provided with appliances
for cutting off at will the entry into it of products of combustion and of completely
closing the opening at one of its ends so as to admit of its being converted at will
into a vessel having only one open aperture.
To avoid the evils which result from the access into or passage through the vessel
in which sulphide of sodium is being produced of either air or products of com-
bustion I heat the sulphate of soda and the carbonaceous matter separately in
distinct furnaces, and I then mix them together only after they have separately
been raised to such temperature or temperatures as shall permit of the reaction
between them taking place without any further application of heat. I am thus
enabled to effect the reaction between them in a vessel into which neither air nor
products of combustion can enter while the reaction is going on, and which for the
Lime being has no other opening than such as is necessary for the escape of the
gascous product of the reaction. I thus not only obtain a purer sulphide than has
ever hitherto been produced but I obtain at the same time a practically pure
carbonic acid by means of which the sulphide can afterwards be decomposed.
For this method of working the carbonaceous matter employed must be powdered
čoke or other form of charcoal This I heat in the suitably lined revolving furnace
aforesaid. The furnace in which I heat the sulphate of soda should preferably be
a Siemens's regenerative furnace. In it I heat the sulphate of soda at least to
fusion The furnace in which I thus heat-the sulphate of soda is so connected
with the revolving furnace that the fused sulphate of soda can be run from the
former furnace into the latter at will. A means which will be more particularly
described in my Final Specification is also provided, whereby products of com-
bustion can be supplied at will to the revolving furnace, such products of combustion
being either those of the furnace in which the sulphate of soda is heated or those
of a third furnace, whose special function shall be the supply of products of com-
bustion to the revolver By means of such products of combustion, which should
preferably be either in a deoxidizing state or as nearly neutral as possible, I heat
the powdered coke in the revolving furnace, preferably to bright redness. I then
cut off the supply of products of combustion to the revolving furnace, close it at
one of its ends, run in upon the hot coke in it fused sulphate of soda from the other
furnace, and then put the revolving furnace into as rapid motion as I conveniently
can in order to mix the hot powdered coke and the fused sulphate of soda thoroughly
together as quickly as possible. If the sulphate of soda and the hot coke have been
sufficiently heated before being thus brought into contact one with the other the
heat previously communicated to them separately will suffice for the completion of
the required reaction between them; but if they have not been sufficiently heated
before being so brought together it may be necessary after the reaction has proceeded
as far as it can to admit for a few moments products of combustion.
The above described manner of carrying out my Invention I believe to be the
best, but it may be varied in several ways. Thus the furnace in which the sulphide
of sodium is formed may be other than a revolving furnace, and the furnace in
which the sulphate of soda is fused may be other than a Siemens's furnace, and the
fui nace in which the powdered coke or charcoal is heated may be other than that
in which it afterwards reacts on the sulphate of soda. Instead too of the fused
sulphate of soda being added to the hot coke the hot coke may be added to the
fused sulphate of soda Moreover, if the sulphate of soda be sufficiently heated,
which however will be difficult to effect, the heating of the coke or charcoal may
be dispensed with.
This Invention is equally applicable to the manufacture of sulphide of potassium.

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.
.
WALTER WELDON, of Abbey Lodge, Merton, in the County of Surrey. "IM-
PROVEMENTS IN THE MANUFACTURE OF SULPHIDE OF SODIUM AND SUPHIDE OF
POTASSIUM, CONSISTING PARTLY IN A NEW METHOD OR PROCESS AND PARTLY IN
MEANS AND APPLIANCES FOR CARRYING THE SAME INTO EFFECT."
This Invention relates to a new method or process for the manufacture of
sulphide of sodium by the reaction of carbonaceous matter upon sulphate of soda,
and for the manufacture of sulphide of potassium by the reaction of carbonaceous
matter upon sulphate of potash, and to means and appliances for carrying this new,
method or process into effect.
In describing the said Invention it will be convenient to speak only of sulphate
of soda and sulphide of sodium, but all that is said of these will be equally
applicable to sulphate of potash and sulphide of potassium.
The first part of the said Invention consists in obtaining sulphide of sodium by
bringing into mutual contact in a furnace or vessel, which for the time being has no
opening except that necessary for the passing away of the gaseous product of their
reaction, sulphate of soda and powdered coke or charcoal, each of which before
being brought into contact with the other has been heated separately, the sulphate
of soda in one furnace, and at least to fusion, and the coke or charcoal in another
furnace, and preferably to redness, so that when the previously heated sulphate of
soda and the previously heated coke or charcoal are mixed together as just said,
reaction may take place between them and may be carried to completeness without
any further or with but little further application of heat.
The second part of the said Invention consists in the appliances and manner of
working for carrying into effect the said new method of obtaining sulphide of
sodium by means of a combination of a revolving furnace with two other furnaces,
one for supplying the evolving 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 Siomens's regenerative furnace, and it may be so
disposed as to be capable of supplying products of combustion to the revolving
furnace when necessary, 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 differ therefrom
in being lined and otherwise arranged and disposed, as is set forth in the Specifi-
cation of my Patent, numbered 3380, of the year 1876. It must be lined interiorly
with blocks of agglomerated and hardly compressed coke to protect it from
corrosion by the sulphide to be formed 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 pro-
Jecting 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 fuinace, as is the case with the annular disc when such annular disc is
use;
this carbon disc when in use is attached to the revolving furnace by means.
in

page_text: •
of the bolts aforesaid in such wise as to revolve with the furnace when the furnace
is in revolution, 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 end of the revolving
furnace by which, when products of combustion are passing into the revolving
furnace, they afterwards pass out of it, must cominunicate 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. The 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 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.
The two furnaces being thus arranged and disposed, the method of working will
consist of charging sulphate of soda into the Siemens's furnace, and therein heating
it at least to fusion; in charging powdered coke or charcoal into the revolving
furnace, and admitting into that furnace products of combustion until the powdered
coke or charcoal has become heated to redness, the revolving furnace during this
operation communicating with the chimney, and being either kept motionless or
revolving only extremely slowly; in then cutting off the supply of products of
combustion to the revolving furnace, closing the aperture by which they had
entered by means of the carbon disc aforesaid, and at the same time interrupting
the communication of the other end of the furnace with the chimney and
establishing instead thereof communication with the apparatus for receiving carbonic
acid, and in then running into the revolving furnace fused sulphate of soda from
the Siemens's furnace, and putting the revolving furnace into somewhat rapid
revolution. Reaction between the fused sulphate of soda and the hot coke or
charcoal will now take place in what for the time being is a close furnace, having.
no opening except that necessary for the passing away of the gaseous product of
the reaction. If the sulphate of soda and the coke or charcoal have been sufficiently
heated before being thus brought together reaction between them will go on to
completeness without any further application of heat. If they have not been
sufficiently heated when the reaction between them has proceeded as far as it
otherwise can, the communication of the revolving furnace with the carbonic acid
apparatus must be interrupted and its communication with the chimney re-esta-
blished, and products of combustion must be admitted for such time as may be
necessary to complete the reaction.
When it is not desired to utilize the gaseous product of the reaction the revolving
furnace will of course always communicate with the chimney, instead of sometimes
with the chimney and sometimes with other apparatus, as above set forth.
The above described manner of carrying into effect the new method of obtaining
sulphide of sodium, which is above set forth, may be varied in several 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 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.

page_text: Having now described the nature of my said Invention, and in what manner the
same is to be performed, I claim as the Invention to be secured to me by the
herein-before in part recited Letters Patent,—
Firstly. Obtaining sulphide of sodium and sulphide of potassium by bringing
into mutual contact in a furnace or vessel, which for the time being has no opening
except that necessary for the passing away of the gaseous product of their reaction,
sulphate of soda or sulphate of potash and powdered coke or charcoal, each of
which, before being brought into contact with the other, has been heated separately,
the sulphate of soda or potash in one furnace, and the coke or charcoal in another
furnace, as is above set forth
And, Secondly. The use for this method of obtaining sulphide of sodium by
means and appliances substantially as above described.
In witness whereof, I, the said Walter Weldon, 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.