IMPROVENENTS IN OBTAINING CAUSTIC SODA AND OTHER SUBSTANCES
Year: 1852

page_text: LETTERS PATENT to William Chisholm, of Cornwall Place, Hollo-
way, in the County of Middlesex, Chemist, for the Invention
of "IMPROVENENTS IN OBTAINING CAUSTIC SODA AND OTHER SUBSTANCES
"
Sealed the 13th April 1853, and dated the 19th October 1852.
PROVISIONAL SPECIFICATION left by the said William Chisholm
at the Office of the Commissioners of Patents, with his Petition,
on the 19th October 1852.
I, WILLIAM CHISHOLM, do hereby declare the nature of the said
Invention for "IMPROVEMENTS IN OBTAINING CAUSTIC SODA AND OTHER
SUBSTANCES FROM THE RESIDUES OF ARTICLES USED IN THE PURIFICATION OF
GAS" to be as follows:-
In a former demand for Patent for purifying gas I have described a
purifying mixture, consisting of chloride of sodium and charcoal, for
depriving gas of its ammonia. After this mixture has done its office
at the gas works, I place it in a proper vessel and sublime from it by

page_text: heat its salts of ammonia; the residium will be carbonate of soda and
charcoal; the soda may be washed out of the charcoal either by steam
or hot or cold water, and soda ash or crystallized soda obtained from
the solution by evaporation. The damp charcoal from which the car-
bonate of soda has been washed may now be mixed with about its
own weight of chloride of sodium and placed in a close vessel, into
which carbonic acid is to be passed so as to saturate the mixture. The
sublimed salts of ammonia, as above described, are to be placed in
another vessel and mixed with lime; this vessel will be connected by a
tube with the one containing the chloride of sodium, charcoal, and
carbonic acid. Heat is now to be applied to the lime and ammonia
vessel, when caustic ammonia will pass over, and in its passage through
the mixture of chloride of sodium, charcoal, and carbonic acid will
first be converted into a carbonate and bicarbonate, and, lastly, into a
hydrochlorate of ammonia, converting the chloride of sodium into a
carbonate of soda. The salts of soda and ammonia are to be seperated
in the manner already described. This process may be repeated add
infinitum, merely supplying any loss of ammonia by adding a little
purifying mixture from the gas works, or any of the crude salts of
ammonia of commerce.
The residium arising from the lime and salts of ammonia may be
used for the purification of gas, as described in my Patent before-
mentioned.
Any vegetable charcoal or peat, partially charred or simply dried (I
prefer peat charcoal), roughly ground, mixed with sulphate or hydro-
chlorate of ammonia of commerce, may be used for the manufacture of
soda instead of the purifying mixture.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said William Chisholm in the Great Seal Patent Office
on the 18th April 1853.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I,
WILLIAM CHISHOLM, of Cornwall Place, Holloway, in the County of
Middlesex, Chemist, &c., send greeting.

page_text: WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Nineteenth day of October, in the year
of our Lord One thousand eight hundred and fifty-two, in the six-
teenth year of Her reign, did, for Herself, Her heirs and successors,
give and grant unto me, the said William Chisholm, Her especial license
that I, the said William Chisholm, my executors, administrators, and
assigns, or such others as I, the said William Chisholm, my executors,
administrators, and 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 "AN IMPROVED
MODE OF OBTAINING CAUSTIC SODA AND OTHER SUBSTANCES FROM THE
RESIDUE OF ARTICLES USED IN THE PURIFICATION OF GAS," upon the con-
dition (amongst others) that I, the said William Chisholm, by an
instrument in writing under my hand and seal, 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 Chisholm, 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:
The particulars of my Invention will be found by reference, first, to
an abstract, as follows, of the Specification of a Patent granted to me
on or about the
day of October, One thousand eight hundred
and fifty-two, for limprovements in the Purification of Gas, and the
Obtention of certain Products during the Process of such Purification.
In such Specification I state that for the purposes of that Invention I
use charcoal made from peat partially charred, or charcoal made from
algoe (seaweed), either in blocks, or coarsely powdered, or finely ground.
In this process I prefer to use peat charcoal, to which I add chloride
(common salt), and for the purposes of this Invention I use equal parts
of each. This mixture will be placed in that vessel, well known on all

page_text: gas works as the dry lime purifier, and the gas is made to play through
it in a similar manner or through the lime now used, which, being
effected, a decomposition takes place; the chloride of sodium is decom-
posed by the hydrosulphuric of ammonia contained in the gas; a
hydrochlorate of ammonia and hydrosulphate of soda are formed.
After the mixture herein described has done its office at the gas
works I cause all the soluble salts to be separated from the mixture,
either by passing steam through it or washing it with hot or cold water.
The solution to be evaporated to dryness and then placed in the well
known apparatus for subliming "sal ammoniac"; when heat is applied
the hydrochlorate of ammonia will be sublimed and the caustic soda
remain in the retort. This process may be done with the mixture as
it comes from the gas works without washing out the salts first, in
which case the mixture remaining in the retort, after subliming from it
the hydrochlorate of ammonia, will be soda and charcoal; the former
must be washed out and evaporated or crystallized. The damp charcoal
from which the salts of ammonia and soda has been separated may be
again mixed with chloride of sodium, as described in the Specification
of the Patent herein in part recited, for purifying gas, and applied at the
gas works again, plan-retort. The sublimed hydrochlorate of ammonia
may be sold, or the charcoal may be mixed with the chloride of sodium
and placed in a retort, and the ammonia obtained as above described
by sublimation mixed with rather more than its own weight of car-
bonate of lime and placed in another retort. The two retorts are to be
connected with a short and wide tube; a fire is to be placed under the
retort containing the ammonia and carbonate of lime, when the am-
monia will be decomposed, the hydrochloric acid combining with the
lime, and the ammonia with the carbonic acid; the volatile carbonate of
ammonia will pass over into the retort containing the charcoal and
chloride of sodium, when the chloride of sodium will be decomposed,
its chlorine combining with the ammonia, and the carbonic acid com-
bining with the soda. The contents of the retort which contained the
ammonia and carbonite of lime will now be chloride of calcium, and
may be sold. The contents of the retort which contains the charcoal
must be treated precisely in the same manner as described in the first

page_text: part of the Patent aforesaid, as if the mixture had taken up the am-
monia from purifying the gas. This process may be a continuous one,
any little ammonia that may be lost in the process of manufacture
being made good by a supply of the purifying mixture that has been
used at the gas works, or from a sulphate or chloride of ammonia of
commerce. Instead of carbonate of lime, as described to be used with
the ammonia in one of the retorts, lime may be used, when caustic
ammonia will pass over instead of a carbonate. In this case a stream
of carbonic acid must be continued playing into the retort containing
the charcoal and chloride of sodium during the operation. Instead of
using the purifying material from the gas works which has been
charged with ammonia from the purification of gas, a commercial chlo-
ride or other salt of ammonia may be used, such ammonia being the
same weight as the chloride of sodium to be acted upon. The opera-
tion will be precisely the same, the ammonia being always recovered,
and may be used over and over as may be required.
In witness whereof, I, the said William Chisholm, have here-
unto set my hand and seal, this Eighteenth day of April, in
the year of our Lord One thousand eight hundred and fifty-
three.
Witness, JOHN GEDGE,
Patent Agent,
4, Wellington Street, Strand,
London.
W CHISHOLM. (L.s.)