CERTAIN IMPROVEMENTS IN THE CONVERTING SULPHATE OF SODA INTO THE SUBCARBONATE OF SODA OR MINERAL ALKALI
Year: 1836

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, I, THOMAS
HODGSON LEIGHTON, of Blyth, in the County of Northumberland, Chemist,
send greeting.
WHEREAS His most Excellent Majesty King William the Fourth, by His
Letters Patent under the Great Seal of Great Britain, bearing date at West-
minster, the Twelfth day of April, in the sixth year of His reign, did, for
Himself, His heirs and successors, give and grant unto me, the said Thomas
Hodgson Leighton, His especial license, that I, the said Thomas Hodson
Leighton, my exors, adñiors, and assigns, or such others as I, the said
Thomas Hodgson Leighton, my exors, admiors, and 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,
exercise, and vend, within England, Wales, and the Town of Berwick-upon-
Tweed, my Invention of "CERTAIN IMPROVEMENTS IN THE CONVERTING SULPHATE
OF SODA INTO THE SUBCARBONATE OF SODA OR MINERAL ALKALI;" in which said
Letters Patent there is contained a proviso, obliging me, the said Thomas
Hodgson Leighton, by an instrument in writing under my hand and seal,
particularly to describe and ascertain the nature of my said Invention, and
in what manner the same is to be performed, and to cause the same to be
enrolled in His said Majesty's High Court of Chancery within six calendar
months next and immediately after the date of the said 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
Thomas Hodgson Leighton, do hereby declare that the nature of my
said
Invention, and the manner in which the same is to be performed, are
described and ascertained as follows (that is to say) :-
According to the usual mode of converting sulphate of soda into the
subcarbonate of soda. The sulphate of soda with chalk and coal are
placed in a reverberatory furnace, and by means of heat they are fluxed.
Now, according to my Invention, I use a common reverberatory furnace
having a metal pan or box of a length and width corresponding with the
length and width of the working bed of the furnace, and in depth about
twelve inches, built into the bottom. A steam pipe with a stop-cock in it
(to turn on or shut off steam, as required), leading from a boiler is fitted into
one side of the box or pan, and near to the bottom (under which is a fire, to
prevent the condensation of the steam) there is also a waste pipe, to let off
condensed steam or water. The pan or box is filled with bricks in the follow-
ing manner, to form the hearth or working bed of the reverberatory furnace :-
First, a course of bricks set on edge, and having about an inch space between
each; over these another course is laid flat and close together, upon which
a course of fire bricks set on edge, and also close together, will complete the
furnace bottom. The size of the furnace is immaterial. I use one with a
bed four feet square, the steam pipe one inch and a half bore, the steam
boiler being at a pressure of sixteen pounds to a square inch. The furnace
being heated as heretofore, and the steam shut off, I throw into the furnace
three quarters of a hundredweight of small coal, and half a hundredweight of
fresh burnt lime (chalk will do, but doublo the quantity must be used), and
bring them to a state of complete ignition, when I turn on the steam and
add by degrees one hundredweight of sulphate of soda in powder, stirring it
well into the mixture of coal and lime, or chalk; I continue this operation
until all the sulphate of soda is decomposed, a small portion of the material
being from time to time taken from the furnace and tested, which testing is
done by dissolving it in water, and dropping into the clear solution a little of
the solution of muriate of barytes, which will shew, a precipitate if any
sulphate of soda is left. The mixture in the furnace is not allowed to
melt or flux as heretofore, being prevented by the steam, and by being
stirred with a rake or other instrument; when this part of the process
is complete, I remove the materials from the furnace to a cast iron or
other suitable vat having a pipe at the bottom covered with any common
filter. I have used gravel, and lay over it a cover of the size of the vat, made
of thin sheet iron perforated with small holes; I then run warm water at

page_text: about 150° of heat through the cover into the materials in the vat, so long, as
any alkali or subcarbonate of soda comes off from. it. This is to be ascertained
either by taste or trying the specific gravity of the solution with a hydrometer.;
it may be considered as sufficiently exhausted if the hydrometer does not
exhibit more than two degrees above the ordinary specific gravity of water
used for dissolving. The residuum in the vat is then drained and allowed. to
heat, which it will do, and its being in a proper state will easily be known by
the material smoking and feeling hot; sulphuret of lime is now formed, which
I dissolve by stopping the pipe at the bottom of the vat and running in
boiling water. After, standing about an hour I run it off and repeat the
process until all the sulphuret of lime is washed out of the vat. I collect
all the solution of sulphuret of lime in any convenient reservoir, and add to
it as much muriatic acid as precipitates all the sulphur; the solution of
subcarbonate of soda, or mineral alkali first drawn off being collected into
another vessel is examined, and if found to contain caustic alkali, which is
shewn by its not, effervescing when a small portion of any weak acid is
dropped into it, or sulphur, which may bo shewn by sugar of lead or any
ordinary test. I force in carbonic acid by passing steam through a metal
cylinder charged with charcoal and heated red hot, having a pipe connected
with it and the end immersed in the alkaline solution, or it may be effected
by: adding muriatic or other strong acid-to chalk in a close vessel with a-pipe
leading into the alkaline solution, which is now found to be sufficiently pure
to make chrystals of soda, soap, or for any other purpose for which the
mineral alkali is used.
Having thus described the nature of my Invention, and the manner of
carrying the same into effect, I would remark that I do not confine myself to
the precise means of constructing the furnace in order to the applying steam
by its passing through the joints of the brick at the bottom of the furnace,
and coming amongst the materials therein, as variations may be made in
order to introduce the steam; and I would have it understood that what I
claim as my Invention is,-
First, the application of steam into and with the materials in the furnace
in the process of converting sulphate of soda into subcarbonate of soda or
mineral alkali, as above described.
Secondly, the process of running streams of hot water through the materials
from the furnace, collecting the solution of the subcarbonate of soda, and
purifying the same by forcing carbonic acid as above described; and this means
of purifying I also claim as applicable to the solution of subcarbonate of soda
produced in the ordinary manner from the fluxed materials; and I do

page_text: claim the process of permitting the remaining materials in the vat, after:
drawing off the solution of subcarbonate of soda as I have above described, to:
heat, and again apply hot water, then drawing off the solution of the sulphuret
of lime, whereby I am enabled by precipitation to obtain the sulphur, in the
place of its going into the atmosphere and becoming a nuisance, which is the
case by the present mode of working.
In witness whereof, I, the said Thomas Hodgson Leighton, have hereunto
set my hand and seal, this Eleventh day of October, in the year of our
Lord One thousand eight hundred and thirty-six.