IMPROVEMENTS IN THE MANUFACTURE OF SODA
Year: 1859

page_text: LETTERS PATENT to Alexander Robertson Arrott, of Saint Helen's, in the
County of Lancaster, Chemist, for the Invention of "IMPROVEMENTS IN
THE MANUFACTURE OF SODA." a
Sealed the 29th November 1859, and dated the 3rd June 1859.
PROVISIONAL SPECIFICATION left by the said Alexander Robertson
Arrott at the Office of the Commissioners of Patents, with his Petition,
on the 3rd June 1859.
I, ALEXANDER ROBERTSON ARROTT, of Saint Helen's, in the County of
Lancaster, Chemist, do hereby declare the nature of the Invention for "IM-
PROVEMENTS IN THE MANUFACTURE OF SODA," to be as follows:-
It is well known that sulphuret of sodium in solution can be decomposed by
means of carbonic acid or bicarbonate of soda, carbonate of soda or soda ash
being produced on evaporation, and the sulphur evolved as sulphuretted hydro-
gen; but the great difficulty of carrying out this process has hitherto been the
economical use of sulphuretted hydrogen so produced. I effect this by passing
the gas evolved over oxide of iron heated to redness, or nearly so, in a suitable
furnace or kiln, in which case the sulphur is absorbed by the iron and com-
bines with it, forming an artificial sulphuret; this sulphuret I use for the
formation of sulphate of soda by any of the well-known methods, such as pro-
ducing sulphuric acid from it for the decomposition of common salt, by passing
the sulphurous gas arising from its combustion into leaden chambers, or calciuing

page_text: it in mixture with common salt, whereby sulphate of soda and oxide of iron
are produced, and in working it in the latter manner, I mix the artificial
sulphuret with a suitable quantity of common salt; or I mix the salt with the
oxide of iron previous to passing the sulphuretted hydrogen over it, in which
case I am enabled to roast the mixture and obtain sulphate of soda and
oxide of iron without removing the materials, the absorption of sulphuretted
hydrogen and subsequent oxidation being carried on in the same furnace.
I effect the formation of sulphuret of sodium from sulphate of soda in a
blast furnace, similar to those in use for smelting metals, and I produce caustic
soda from a solution of sulphuret of sodium by means of oxide of iron, the
oxide of iron for this purpose being previously prepared by heating it with an
alkili or alkaline carbonate; or I heat together oxide of iron and sulphuret
of sodium, when caustic soda and sulphuret of iron will be produced; the
caustic soda is then dissolved out; the residuum, which, in either case, con-
sists of sulphuret of iron, is used for the production of sulphate of soda, as
already described. In some cases I form caustic soda from carbonate of soda
by calcining it with peroxide of iron; the caustic soda is dissolved out by
means of hot water, and the peroxide of iron, which remains undissolved, can
be used for the production of a further quantity of caustic soda from carbonate,
or for decomposition of sulphurate of sodium, as already mentioned. The
oxide of iron arising from any of the processes for formation of sulphuric acid
or sulphate of soda is in a fit state to absorb sulphuretted hydrogen without
previous preparation. In these processes, oxide of manganese may be sub-
stituted for oxide of iron.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Alexander Robertson Arrott in the Great Seal Patent Office
on the 3rd December 1859.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, ALEXANDER
ROBERTSON ARROTT, of Saint Helen's, in the County of Lancaster, Chemist,
send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Third day of June, in the year of our Lord, One
thousand eight hundred and fifty-nine, in the twenty-second year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto me,
the said Alexander Robertson Arrott, Her special licence that I, the said
Alexander Robertson Arrott, my executors, administrators, and assigns, or

page_text: such others as I, the said Alexander Robertson Arrott, my executors, admi-
nistrators, 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 "IMPROVEMENTS IN THE MANUFACTURE OF SODA," upon the
condition (amongst others) that I, the said Alexander Robertson Arrott, my
executors or administrators, by an instrument in writing under my, or their,
or one of their hands and seals, 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 Alexander Robertson Arrott, do hereby
declare the nature of the said Invention, and in what manner the same is
to be performed, to be particularly described and ascertained in and by the
following statement thereof, that is to say:-
It is well known that sulphuret of sodium in solution can be decomposed
by means of carbonic acid or bicarbonate of soda, carbonate of soda or soda
ash being produced, and the sulphur evolved as sulphuretted hydrogen, but the
great difficulty of carrying out this process has hitherto been the economical
use of sulphuretted hydrogen so produced.
In operating on salt cake, I prefer to begin by converting the salt cake or
sulphate of soda into sulphuret of sodium by roasting it, in mixture with
coal or coke, in the proportion of about 4 of salt cake to 1 of coal or coke, or
by fusing the same mixture in a cupola or blast furnace, the copula being
supplied with a proper quantity of coke or coal as fuel. The sulphuret of
sodium so obtained I dissolve in water, and expose the solution to the action
of carbonic acid (obtained from any convenient source), which may be con-
veniently done by passing the same down through a tower of iron or brick-
work filled with lumps of coke or pebbles, and causing the carbonic acid gas
to pass upwards amongst the lumps of coke or pebbles, the result of which
is, that the sulphuret of sodium is decomposed and converted into carbonate
of soda, which can be obtained from the solution by the usual well-known
methods, as soda ash or soda crystals, while the sulphur contained in the
sulphuret of sodium is evolved as sulphuretted hydrogen, which is conveyed
from the top of the carbonating tower or apparatus employed by a connecting
pipe to the apparatus in which the sulphur is made to enter into combination
with iron or manganese. Or, I introduce a solution of sulphuret of sodium,

page_text: made as strong as possible, into an iron pot or pan, similar to that used for
the decomposition of common salt by sulphuric acid, and having a pipe con-
nected to convey away the sulphuretted hydrogen evolved. I then add to the
solution of sulphuret of sodium bicarbonate of soda, in the proportion of 85 to
40 of sulphuret of sodium contained in the solution, and, on applying heat,
the bicarbonate of soda is decomposed; and the carbonic acid evolved, by
acting on the sulphuret of sodium, expels the sulphur as sulphuretted
hydrogen, and carbonate of soda remains. I cause the sulphuretted hydrogen
evolved in either of these processes to pass over oxide of iron or oxide of
manganese in small lumps, heated to a low red heat by transmitted heat,
atmospheric air being carefully excluded, by which means sulphuret of iron,
or sulphuret of manganese, or artificial pyrites is produced. I prefer to use
for this purpose a series of kilns similar to those in use for the combustion of
pyrites, but so constructed as that the materials contained in them can be
heated by transmitted heat, and this heat I maintain at a temperature of low
redness. I then cause sulphuretted bydrogen to pass through them in suc-
cession from below upwards, and from time to time I remove at the bottom
a portion of the sulphuret of iron or of manganese produced, when the whole
material in the kilns sinks to the extent of the sulphuret removed, and I
then add a fresh portion of the oxide by an opening at the top, so that the
operation is continuous. When the oxide of iron or of manganese is in
powder, as obtained by the combustion of the sulphurets obtained in the
processes for production of caustic soda, I prefer to heat it in a furnace
similar to the roasting portion of the furnace in common use for the making
of salt cake; and I pass the sulphuretted hydrogen over the surface of the
oxide, heated as already described. The oxide of iron or of manganese when
in lumps may be advantageously converted into sulphuret in a similar furnace.
The sulphurets of iron or of manganese so produced I use for the manufacture
of "salt cake," either by burning them for the production of sulphuric acid,
according to the well-known method at present in use; or I calcine them in
mixture with common salt, by which means I obtain a mixture of oxide of
iron or of manganese and salt cake, from which the salt cake is to be sepa-
rated by lixiviation, the oxide of iron or of manganese remaining insoluble,
and in a proper condition for absorbing sulphur when treated in the manner
already described. I have used the terms oxide of iron and oxide of man-
ganese, by which I mean any oxide of these metals. When I intend to
calcine the sulphuret produced with common salt, I find it advantageous to
mix the oxide and common salt before converting the oxide into sulphuret.
Having thus described the nature of this part of my Invention, and the

page_text: manner of performing the same, I would have it understood that I do not
claim the production of the solution of the sulphuret of sodium, nor the
subjecting it to the action of carbonic acid gas; but what I claim is, the
bringing of the sulphuretted hydrogen, as it is evolved in the manufacture of
carbonate of soda in contact with oxide of iron or oxide of manganese heated
to redness.
To produce caustic soda from "salt cake," I first convert the salt cake by
the means already described into sulphuret of sodium, and this sulphuret of
sodium I bring into contact with oxide of iron or manganese in the following
manner: To a strong solution of caustic soda contained in an iron pot I
add a quantity of peroxide of iron or oxide of manganese, equal in weight to
the soda contained in the solution; I evaporate till the mixture begins to
assume an olive yellow color, and I maintain it in this state till the whole has
assumed this color. I then remove the mass from the pot, and add water,.
when the caustic soda dissolves, and the oxide of iron or oxide of manganese
subsides. This oxide is now in a state to take sulphur from sulphuret of
sodium. The clear solution of caustic soda is drawn off, and to the residual
oxide of iron or oxide of manganese I add solution of sulphuret of sodium so
long as the oxide continues to take up sulphur, whereby a solution of caustic
soda is produced, and sulphuret of iron or sulphuret of manganese is pre-
cipitated, which I use for the production of sulphuric acid or of salt cake, by
calcining it with common salt. I vary this process by adding the dried
mixture of oxide of iron or manganese and caustic soda to a solution of sul-
phuret of sodium without previously removing the caustic soda, thus effecting
a saving of labour; or 1 mix sulphuret of sodium with caustic soda before
heating the solution with oxide of iron or oxide of manganese, and on the
addition of water the whole of the soda dissolves as caustic soda, and sul-
phuret of iron or manganese remains. The sulphuret of iron or manganese
obtained I use for the formation of salt cake, and the oxide of iron produced
by the combustion of the sulphuret I use for the abstracting sulphur from
additional quantities of sulphurets of sodium. I propose also to use for
extracting sulphur from sulphuret of sodium, the formation of caustic soda,
and formation of sulphuret of the metal used, the oxide of iron or man-
ganese which remains in the process hereafter described for obtaining
caustic soda from carbonate of soda. In all these decompositions the oxide
employed should be at least equal to the weight of sulphuret of sodium to
be decomposed.
I obtain caustic soda from carbonate of soda by mixing with the carbonate
peroxide of iron or manganese, and heating to a full red heat, which I con-

page_text: tinue from two to three hours, by which means the carbonic acid is expelled,
and a compound remains, which, on the addition of water, yields caustic soda,
and the metallic oxide remains undissolved; and the manner in which this
is to be performed is as follows:-I mix together in powder an equal weight
of soda ash and peroxide of iron or oxide of manganese, and introduce the
mixture into a retort or furnace. I prefer to use an iron retort similar to
the ordinary iron retort used in the manufacture of coal gas, and I keep the
mixture at a full red heat from two to three hours. When drawn from the
retort, the mixture is placed in water, which I prefer to be boiling; the
caustic soda then dissolves, and oxide of iron or manganese remains insoluble,
and is to be used for decomposing a further portion of carbonate of soda, or
for production of caustic soda from sulphuret of sodium. I greatly prefer
oxide of iron in this process, but if oxide of manganese is used, I admit a
current of air during the roasting.
Having thus described this part of my Invention, I would have it under-
stood that what I claim is, the use of oxide of iron and oxide of manganese
when manufacturing caustic soda, as herein described.
In witness whereof, I, the said Alexander Robertson Arrott, have here-
unto set my hand and seal, this Thirtieth day of November, in the
year of our Lord One thousand eight hundred and fifty-nine.
D ADRATE
L
R. ARROTT. (..)