IMPROVEMENTS IN THE MANUFACTURE OF CAUSTIC SODA AND CARBONATE OF SODA
Year: 1839

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, I, MOSES
POOLE, of Lincoln's Inn, in the County of Middlesex, Gentleman, send
greeting.
WHEREAS Her present most Excellent Majesty Queen Victoria, by Her
Letters Patent under the Great Seal of Great Britain, bearing date at
Westminster, the Ninth day of December, in the third year of Her reign.
did, for Herself, Her heirs and successors, give and grant unto me, the said
Moses Poole, Her especial licence, full power, sole privilege and authority,
that. I, the said Moses Poole, my exors, admors, and assigns, or such others
as I, the said Moses Poole, my exors, adñiors, or assigns, should at any time
agree with, and no others, from time to time and at all times during the
term of years therein expressed, should and lawfully might make, use; exer-
cise, and vend, within England, Wales, and the Town of Berwick-upon-
Tweed, the Invention of "IMPROVEMENTS IN THE MANUFACTURE OF CAUSTIC
SODA AND CARBONATE OF SODA," communicated by a certain Foreigner residing
abroad; in which said Letters Patent is contained a proviso that I, the said
Moses Poole, shall cause a particular description of the nature of the said
Invention, and in what manner the same is to be performed, to be inrolled
in Her said Majesty's High Court of Chancery within six calendar months
next and immediately after the date of the said in part recited Letters Patent
as in and by the same, reference being thereunto had, will more fully and at
large appear.

page_text: NOW KNOW YE, that in compliance with the said proviso, I, the said
Moses Poole, do hereby declare that the nature of the said Invention, and the
manner in which the same is to be performed, are fully described and
ascertained in and by the following statement thereof (that is to say):-
The nature of the Invention of a new method of manufacturing caustic
soda and carbonate of soda consists in the following system or cyclus of
operations by which these products are gained from common salt (that is to say),
I first prepare sulphate of soda by the mutual decomposition of common salt or
chloride of sodium and sulphate of ammonia, by which decomposition sulphate
of soda and hydrochlorate of ammonia are produced. The sulphate of soda is
then converted into sulphuret of sodium by heating it with charcoal or any other
carbonaceous substance, and this sulphuret of sodium is decomposed by the pro-
toxide of copper, by which decomposition caustic soda is formed, which if requi-
site may be evaporated to solid caustic soda, or saturated with carbonic acid and
thus converted into carbonate of soda. The sulphuret of copper afforded by the
decomposition of sulphuret of sodium and protoxide of copper is then calcinated
in a current of atmospherical air, by which operation deutoxide of copper is
formed, the sulphur being burned and volatilized in the state of sulphurous
acid gas. I then combine this latter acid with caustic ammonia gained by the
decomposition of the hydrochlorate of ammonia by means of lime, exposing
hereafter the sulphate of ammonia thus gained to the action of atmospherical
air, and regain sulphate of ammonia, which is then again used for decomposing
common salt. Lastly, the deutoxide of copper is converted into the state of
protoxide by moderate heating with a certain quantity of coal. The same
cyclus of operations may then be recommended, the ammonia as well as the
protoxide of copper and the greater part of the sulphur being recovered. I
shall now give a more detailed description of this process or processes divided
in the following seven parts:-
.
First part. As the conversion of common salt into the state of sulphate of
soda by its mutual decomposition with sulphate of ammonia is a well-known
process, a description of it will be superfluous. The hydrochlorate of ammonia
gained hereby is used afterwards for restoring sulphate of ammonia, as will
hereafter be described.
Second part. The decomposition of sulphate of soda by means of heating
it with coal, charcoal, turf coal, coke, or any other sort of carbon, is likewise a
well-known process, but I recommend to effect this decomposition in. any
closed vessel in order to prevent the loss of a good quantity of sulphur which
would otherwise be burned and thus volatilized.
Third part. The sulphuret of sodium gained by the latter operation is

page_text: then dissolved in water and filtrated in order to separate the remainder of coal
(which may be employed for subsequent operations), whereupon protoxide of
copper in the state of fine powder is added to the liquid slowly and in little
portions, and by well stirring the matter until the decomposition of the sulphuret
of sodium will be just found to be completely effected, by adding to a small portion
of it some drops of a solution of sulphate of copper, which, if the decomposition
is not yet finished, will produce a precipitate of a blackish colour, but will
give a precipitate of a pure blue colour if the decomposition of the sulphuret
of sodium is completely done. The sulphuret of copper is then separated
from the liquid containing caustic soda by filtrating or in any other convenient
manner.
Fourth part. The solution of caustic soda may then be evaporated to
dryness in case of solid caustic soda being required. If carbonate of soda.
should be wanted, the solution of caustic soda is to be saturated with carbonic
acid. Although any manner for causing caustic soda to get in contact with
carbonic acid may be adopted, I prefer to make use of a large vessel or
chamber constructed of bricks, and covered on the inside with Roman cement
or any other convenient substance, filled up with pieces of granite, limestone,
or any other sort of stone, excepted only such sorts of stones which could be
considerably attacked by the caustic liquid. I suffer the liquid to flow gently
over the stones, and at the same time I introduce a current of carbonic acid
gained by the combustion of coal, coke, charcoal, or any other convenient
combustible on the inferior end of the chamber. The carbonic acid passing
the interstices of the stones will thus be absorbed by the caustic soda, carbo-
nate of soda being formed, which hereafter may be evaporated and calcinated
in the usual way.
Fifth part. The sulphuret of copper gained as described in the third part
of this Specification is now to be converted into deutoxide of copper by cal-
cinating it in such a way as to allow the sulphurous acid gas produced by.
this calcination to be received in the apparatus destined for the preparation of
sulphate of ammonia. I effect this calcination in an iron muffle heated to a
feeble degree of glowing, and I cause a slow current of atmospherical air to
pass through the muffle and then into the apparatus, which will be described
in this sixth part of this Specification. The sulphate of copper which may
form a couch of about one inch in the muffle is to be well stirred until the
smell of sulphurous acid is observed to have ceased. The deutoxide of
copper is then taken out of the muffle, and a new portion of sulphuret is
introduced in such a way that the muffle may be kept in continual heat. It
is now to be remarked that the deutoxide of copper brought into contact with

page_text: the protosulphuret of sodium would decompose this latter so as to form
a considerable quantity of hyposulphate of soda mixed with caustic soda. It
is in order to prevent this byphosulphate of soda from being produced
thus I employ the protoxide of copper, which is obtained by mixing the
deutoxide of copper with about one twenty-eight of its weight of powdered
charcoal or turf coal, and by heating this mixture in a well-closed vessel of
iron, or any other suitable material, to a feeble degree of glowing.
Sixth part. I have already observed that the sulphurous acid gas formed
by the calcination of sulphuret of copper is to be received in any apparatus,
in order to be saturated with ammonia. I get this ammonia by distilling the
hydrochlorate of ammonia, gained as described in the first part of this Speci-
fication, with caustic lime. In order to combine this ammonia with the
sulphurous acid I employ a large vessel or chamber constructed of lead or any
other suitable material, filled with chipping of fir wood. By means of a ven-
tilating apparatus I cause a moderate current of atmospherical air to pass over
the glowing sulphuret of copper in the muffle, as is above described, and
after being sufficiently cooled by passing through a pipe surrounded with cold
water, to move slowly through the interstices of the chipping at the same time
the caustic ammonia (the caustic ammonia) is introduced on the upper end
of the chamber, and gliding slowly over the chipping, it absorbes the
sulphurous acid, and is thus converted into the state of sulphate of ammonia.
In order to prevent any loss of ammonia that could be caused by the current
of the air leaving the chamber, I employ a second chamber; or if it should be
found convenient, several chambers of the same construction as the first, and
also filled with chipping, through which the current of air is forced to pass, and
over the chipping of which a very feeble solution of sulphuric acid in water is
caused to flow. By this means the ammonia, which could have been carried
off by the air leaving the first chamber, is entirely absorbed and thus saved,
sulphate of ammonia being formed, which may be added to the solution of
sulphate of ammonia, the preparation of which forms the last part of the process.
Seventh part. This process, consisting in the oxydation of the sulphate of
ammonia to sulphate, is very easily performed by exposing a solution of the
former salt to the contact of the atmospherical air. I employ for this purpose
a frame or scaffold, constructed of timber in any convenient manner, which I fill
with chipping of fir wood in such a way as to expose this chipping as much as
possible to the access of atmospherical air. The solution of sulphate of
ammonia is then caused to flow gently over the chipping, and being received.
in a flat chest placed below the chipping, is pumped up again until it is
observed to be entirely converted into sulphate of ammonia, which is hereafter

page_text: used for decomposing common salt, as is herein-before described. The manner
of trying the sulphate of ammonia, or its being perfectly formed, consists in
the addition of some drops of sulphuric acid to a small portion of the liquid.
If by this solution a smell of sulphurous acid should be observed, the oxydation
is not yet entirely finished.
I do not claim as the Invention the mode of preparing sulphate of soda
by the decomposition of common salt and sulphate of ammonia, nor do I claim
the conversion of sodium, nor the calcination of sulphuret of copper, nor do I
claim any particular construction of apparatus which may be used for the
process, nor do I claim certain proportions in which the substances used for
the process may be applied. But I claim as the Invention, consisting of
certain improvements in the manufacture of caustic soda and carbonate of
soda, the decomposition of sulphuret of sodium by the protoxide of copper, and
in combination with this process the production of sulphate of ammonia, and
also in the conversion of sulphate of ammonia to the state of sulphate by the
manner herein-before described.
In witness whereof, I, the said Moses Poole, have hereunto set my
hand and seal, this Fourth day of
in the year of our Lord