CERTAIN IMPROVEMENTS IN MANU- FACTURING SULPHURIC ACID
Year: 1853

page_text: LETTERS PATENT to William Hunt, of Lee Brook Chemical Works,
near Wednesbury, in the County of Stafford, Manufacturing
Chemist, for the Invention of "CERTAIN IMPROVEMENTS IN MANU-
FACTURING SULPHURIC ACID."
nea
cunest
Stanford, Manufacturing
Chemist, for the Invention of "CERTAIN IMPROVEMENTS IN MANU-
FACTURING SULPHURIC ACID."
Sealed the 9th January 1854, and dated the 16th August 1853.
PROVISIONAL SPECIFICATION left by the said William Hunt
at the Office of the Commissioners of Patents, with his Petition,
on the 16th August 1853.
I, WILLIAM HUNT, do hereby declare the nature of the said Inven-
tion for "CERTAIN IMPROVEMENTS IN MANUFACTURING SULPHURIC ACID "
to be as follows:-
The ordinary mode of making sulphuric acid is to burn brimstone
or sulphury pyrites to obtain sulphurous acid; and it has been found
necessary to use a considerable quantity of nitrate of soda or nitrate of
potash (commonly called nitre), which is decomposed to yield nitrous
gases to mix with the sulphurous acid gas and atmospheric air to
facilitate the formation of sulphuric acid, which is conveyed along flues
Sp

page_text: for cooling, and thence to the vitriol chamber for condensation. The
quantity of nitre used for this purpose forms a considerable part of the
expense incurred in manufacturing sulphuric acid. And further, by far
the greatest quantity of sulphuric acid now made is obtained from
sulphury pyrites; but sulphuric acid made from this substance is found
to contain arsenic, and it is well known that such acid containing
arsenic cannot be used in some of the arts, such as preparing iron for
tinning and galvanizing. Now my improvements are intended, first,
to diminish the cost of nitre in manufacturing sulphuric acid; and,
secondly, to extract the arsenic from sulphuric acid.
In carrying my improvements into effect I propose to cause sul-
phuric acid gas and atmospheric air to pass through a hot chamber or
flue made with brick, and filled with pebbles or pumice stone, or any
other material that will resist the action of heat and acid. I purpose
heating the flue or chamber and materials by utilizing the heat given
off when burning sulphury pyrites from which the sulphurous acid gas
is obtained, and causing the sulphurous acid and atmospheric air to
pass through the chamber when red hot. By this means part of the
sulphurous acid gas takes up oxygen from the air, and becomes sulphuric
acid, which is carried forward with some sulphurous acid into the
vitriol chamber, where it condenses, and the remaining sulphurous acid
becomes mixed with nitrous gas, as in the ordinary way, but I save
nitre in proportion to the sulphuric acid made in the hot chamber or
flue. Hitherto the gases have been cooled down in flues as they are
generated, and not passed through a hot chamber.
To effect a larger saving of nitre, I propose to pass sulphurous acid
gas and atmospheric air through a brick flue or chamber filled with
the former mentioned materials, and heated by the spare heat arising
from the manufacture of coke or other ovens or furnaces. The above
gases percolating through the heated materials become sulphuric acid
gas, which being cooled after leaving the flue, and brought into contact
with water, is rapidly absorbed, and becomes liquid sulphuric acid.
I also propose to make sulphuric acid by using strong sulphuric acid
as an absorbent of sulphurous acid. I purpose using the sulphuric acid

page_text: at a strength of about 134° on Twaddle or upwards, and employ it
whether free of or containing nitrous gas. In carrying out this process
I cause sulphurous acid gas and atmospheric air to percolate through coke
moistened with strong sulphuric acid from time to time. The sulphuric
acid gas becomes absorbed by the sulphuric acid, and absorbs oxygen
from the atmospheric air, and is converted into sulphuric acid; the same
sulphuric acid may be used again for absorbing. The production of
sulphuric acid with these means is in proportion to the oxidation of the
sulphuric acid.
In order to separate arsenic from sulphuric acid I cause the acid
to percolate through a bed of pebbles in contact with a stream of
sulphuretted hydrogen, and to the extent that arsenic is present sul-
phuretted hydrogen will be decomposed. The sulphur will combine
with the arsenic, and form what is called yellow orpiment, which
separated from the sulphuric acid by filtration; the sulphuric acid is
then in a proper state for evaporation.
may be
I obtain sulphuretted hydrogen for this purpose by operating upon
sulphuret of calcium with muriatic acid or by any other well-known
means of generating sulphuretted hydrogen.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said William Hunt in the Great Seal Patent Office
on the 16th February 1854.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I,
WILLIAM HUNT, of Lee Brook Chemical Works, near Wednesbury,
in the County of Stafford, Manufacturing Chemist, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Sixteenth day of August, in the year
of our Lord One thousand eight hundred and fifty-three, in the seven-
teenth year of Her reign, did, for Herself, Her heirs and successors,
give and grant unto me, the said William Hunt, Her special license
that I, the said William Hunt, my executors, administrators, and
assigns, or such others as I, the said William Hunt, my executors, ad-
ministrators, and assigns, should at any time agree with, and no others,

page_text: .
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 "CERTAIN IMPROVEMENTS IN
MANUFACTURING SULPHURIC ACID," upon the condition (amongst others)
that I, the said William Hunt, 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 Hunt, 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, reference being had to the Drawings hereunto
annexed, and to the letters and figures marked thereon (that is to say);
The ordinary mode of making sulphuric acid is to burn brimstone or
sulphury pyrites in order to obtain sulphurous acid gas, which is subse-
quently converted into sulphuric acid by the addition of oxygen
obtained from any suitable source.
The oxygen has usually been obtained from nitrate of soda or nitrate
of potash (commonly called nitre), of which a large quantity is required
to be decomposed to yield nitrous gases to mix with the sulphurous
acid gas; atmospheric air is also introduced to facilitate the formation
of sulphuric acid. These various gases are conveyed along flues in
order to be cooled, and pass from thence to the vitriol chamber, where
the sulphuric acid is condensed. The quantity of nitre used for this
purpose forms a considerable part of the expence incurred in manufac-
turing sulphuric acid; any means, therefore, of economizing this
article will of course materially reduce the cost of manufacture.
A large proportion of the sulphuric acid now made is obtained from
sulphury pyrites, but sulphuric acid made from this substance is found
to contain arsenic, and it is well known that such acid containing
arsenic cannot be used in some of the arts, such as preparing iroit for
tinning and galvanizing.

page_text: Now my improvements are intended, first, to obviate the necessity of
using so large a quantity of nitre as is usually employed in manufac-
turing sulphuric acid; and, secondly, to extract the arsenic from sul-
phuric acid so that it may be more applicable to the various purposes
for which it is usually employed.
In carrying my improvements into effect I propose to cause sul-
phurous acid gas and atmospheric air to pass through a hot chamber or
flue made of brick or other suitable material, and, if thought desirable,
filled with pebbles or pumice stone or any other material that will
resist the action of heat and acid. This flue or chamber, and materials.
contained therein, are heated by means of the heat given off from the
furnace while burning the sulphury pyrites from which the sulphurous
acid gas is obtained. The sulphurous acid gas, together with the
atmospheric air, are caused to pass through this heated chamber, which
is made nearly red hot. By this means part of the sulphurous acid gas.
is made to take up oxygen from the air more readily than when the
gases are comparatively cool, and is converted into sulphuric acid,.
which is carried forward with some sulphurous acid into the vitriol
chamber or to the condensing column hereafter described, where it is.
condensed. The remaining sulphurous acid will also become mixed
with nitrous gas, which is supplied for the purpose. By this means a
great economy of nitre is effected, as a considerable quantity of.
sulphuric acid is made in the hot chamber or flue by the combination
of the oxygen of the atmosphere with the sulphurous acid. Hitherto
the gases have been cooled down in flues as they were generated, and
not passed through a hot chamber; the consequence was that the
oxygen of the air would not easily combine with the sulphurous acid, as
this combination will only take place with avidity when the gases are
highly heated.
A large saving of nitre may also be effected by causing the sulphurous.
acid gas and atmospheric air to pass through a brick flue or chamber
filled with the former-mentioned materials, and heated by the spare
heat arising from the manufacture of coke, or from other ovens.or
furnaces. By either of these means the heat required to promote the
combination of the oxygen of the air with the sulphurous acid is ob-
tained from sources where it would otherwise be wasted. The above

page_text: gases by percolating through the heated materials become converted
into sulphuric acid gas, which being cooled after leaving the flue, and
brought in contact with water, will be rapidly absorbed, and become
converted into liquid sulphuric acid.
Fig. 1, Sheet I., represents a longitudinal section of a furnace con-
structed according to my improvements for burning coaly pyrites. and
generating sulphurous acid gas therefrom. Fig. 2, is a transverse
section of the same. a, a, a, is the masonry of the furnace; b, b, b, the
fire bars or grating on which the pyrites are placed; c, c, c, are ash pits,
through which the dust resulting from the burning of the pyrites falls,
and may be cleared out from time to time through the side doors
d, d, d. The furnace is charged with pyrites by the door e, (Fig. 1,) in
front; and air to support combustion, and also to supply oxygen to carry
on the conversion of the sulphurous acid into sulphuric acid, is supplied
through a door opening or hole below the furnace door communicating
with the ash pits. As the sulphur from the pyrites becomes driven off
therefrom, and converted into sulphurous acid gas, the exhausted pyrites
are pushed forward along the grating towards the end to make room
for a fresh supply; and to facilitate this operation side doors g, g, g, are
placed on the side of the furnace so as to enable the workmen to stir
and push forward the burnt and exhausted pyrites, and when the mass
has been deprived of all its sulphur it is finally pushed into the well h,
from whence, when cool, it may be removed in any convenient manner.
The heated gases pass from the furnace along the flue i, i, i, made
above the fire, as seen in the Figures, and by this means the gases are
made exceedingly hot, and caused to combine with the oxygen of the
air supplied to the furnace, and thereby produce sulphuric acid. This
flue or chamber may, if thought desirable, be supplied with pebbles,
stones, or other substances, through or between which the gases will be
made to pass, and thereby be more effectually commingled. By thus
placing the flue or chamber i, i, above the furnace the heat of the
latter is made more uniform than it otherwise would be, and will more
effectually burn the carbonaceous matters contained in the pyrites; and
as a considerable portion of the sulphurous acid gas will be converted
into sulphuric acid in the furnace, a less quantity of nitre or nitrous gas
than usual will be required.

page_text: If it be proposed to use a vitriol chamber in connection with this
apparatus, the gases are conveyed away from the fluc i, through the
opening j, (Fig. 1,) direct to the vitriol chamber, which must be sup-
plied with nitrous gas in the ordinary way; but I propose further to
economize the heat of the furnaces and gases by causing the latter to
enter another chamber k, (Fig. 2,) in which I place pots 1, 7, filled with
nitre, which being acted upon by the heated gases will give off nitrous
gas in great quantities. A portion of this nitrous gas will combine
with the sulphurous acid gas, and be converted into sulphuric acid gas
in the chamber k, from whence, with the uncombined gases, it will be
conveyed through the flue m, to the condensing chamber.
Fig. 3, is a longitudinal section, and Fig. 4, a transverse section of
another arrangement of apparatus for facilitating the combination of the
oxygen of the air with sulphurous acid gas. This apparatus may be
used either alone or in combination with that above described. In order,
however, to avoid complexity I will explain its operation when used alone.
The object of this arrangement is to utilize the waste heat given off*
from coke ovens, and which is usually allowed to escape uselessly along
the flue to the chimney, and from thence into the atmosphere. The
sulphurous acid gas from the ordinary furnace, or from my improved
furnace above described, is conveyed in combination with atmospheric
air along a flue or chamber which is heated by the waste heat of the
coke ovens. a, a, (Figure 3,) is the furnace for burning the sulphury
pyrites, the gases from which pass along a flue or narrow chamber i, i,
filled with pebbles, stones, or other material not liable to be acted upon
by heat or the acid. Above and below this flue or chamber i, i, are
other flues or chambers n, n, which communicate with the coke ovens,
as shewn at 0, 0, 0. As the heated gases from the ovens pass along the
flues n, n, they heat the sulphurous acid gas and atmospheric air in
the central flue i, i, and thereby facilitate the combination of the gases
and conversion of the sulphurous acid into sulphuric acid.
It will be understood from the foregoing description that the sul-
phurous gases from the furnace are heated in their own flue by the
heat passing along the flues from the coke ovens. Sometimes, however,
I dispense with a separate flue, and propose to carry the sulphurous

page_text: gases direct from the furnace into the flue from the coke ovens; and as
all the combustible gases will be consumed in the flue, the sulphurous
and sulphuric acid gases will be conducted from the flue to a con-
denser in which the sulphurous acid will have an additional dose of
oxygen given to it, so as to convert it into sulphuric acid, and this
latter will be condensed by means of water; or in the way hereafter
described.
"
I also propose to make use of strong sulphuric acid in combination
with nitrous gas or nitric acid as an absorbent of sulphurous acid,
which, in combination with atmospheric air and nitrous gas, is brought
from the furnace into the condensing chamber, in which it meets with
the nitro-sulphuric acid, and whereby the combination is facilitated.
For this purpose I prefer to use sulphuric acid of a strength of about
one hundred and thirty-four degrees or upwards on Twaddle's hydro-
meter. In carrying out this process I cause sulphurous acid gas and
atmospheric air to percolate through a tower or column supplied with
coke.moistened with strong nitro-sulphuric acid, which is made to per-
colate through the mass of coke in the opposite direction. The sul-
phurous acid gas becomes absorbed by the nitro-sulphuric acid, and
absorbs oxygen from the nitrous gas and atmospheric air which accom-
panies it, and is by this means converted into sulphuric acid. The
nitro-sulphuric acid in its passage through the coke will meet with and.
absorb the ascending sulphurous acid, which will receive a dose of
oxygen, and be converted into sulphuric acid. This will run out at
bottom, and will be found charged with nitrous gas, and may be used
again for absorbing an additional quantity of sulphurous acid.
The arrangement of apparatus for carrying out the above object will
be best understood by referring to Sheet 2, of the Drawings, in which
Fig. 5, is a side elevation of the apparatus, the furnace for generating
the nitrous gas being shown on section. Fig. 6, is a longitudinal
vertical section through the whole apparatus. The masonry of the
nitrous gas furnace is shewn at a, a, a; the fire place at b, b. In this
fire place is burned coke or other suitable combustible, and the heat
evolved therefrom passes along the flues i, i, i, which surround a
chamber k, containing any suitable number of pots 1, 1, supplied with

page_text: nitre, which will be decomposed by the heat, and nitrous gas driven
off along the flue in, into the tower or column p, at m, Fig. 6. The
sulphurous gas obtained from any convenient source, and mixed
with atmospheric air, is supplied by the pipe q, to the small tower or
chamber r, which, as well as the column or tower p, is filled with coke,
pebbles, stones, or other substance not liable to be acted upon by the
acid. The uncombined sulphurous acid passes through the chamber 7,
into the lower end of the column or tower p, as seen in Fig. 6, and
while ascending is brought in contact with the nitrous gas supplied at
m, and also meets with a continual. stream of nitro-sulphuric acid, which
is supplied from the upper part, and made to trickle down the mass of
coke or other material contained in the tower. The uncondensed gases
are, by means of a pipe s, conducted from the upper part of the tower
p, to a similar tower p*, where they are again brought in contact with
nitro-sulphuric acid, so that all the sulphurous acid gas will be. con-
verted into sulphuric acid, which will run out at bottom into any con-
venient receptacle. The atmospheric air and other uncondensible
gases are carried off through the pipe t, to the chimney, whereby a suffi-
cient draught is created to cause the gases to pass with facility through
the apparatus and be properly operated upon. Such an excess of
nitrous gas is supplied to the towers through the pipe m, that the sul-
phuric acid that runs out of the towers p, and p*, will be found charged
with this gas; the required quantity of acid may therefore be pumped up
again to the top of the towers to act upon a further supply of sul-
phurous acid, and all the superabundant acid from the towers is con-
ducted to the upper part of the chamber r, and allowed to percolate
through the same, and come in contact with the ascending current of
sulphurous acid, a part of which will be converted into sulphuric
acid, and will fall to the bottom, from whence it may be drawn off* in
any convenient manner.
As the liquid acid, in percolating through the towers, will be con-
tinually increasing in strength, it will be necessary to cautiously supply
from time to time small quantities of water or steam, but care must be
taken that the strength of the acid supplied to the towers is never below
one hundred and thirty-four degrees of Twaddle's hydrometer.

page_text: It will be seen that according to my improved plan of making
sulphuric acid I do not make use of the ordinary vitriol chambers; but
the principle of my improvements may be advantageously applied to the
ordinary manufacture of sulphuric acid, as an excess of uncondensed
sulphurous acid may then be passed through the vitriol chambers into
an apparatus similar to that above described, where all the sulphurous
acid will be quickly converted into sulphuric acid.
By adapting my improvements above described to the vitriol chamber
of an ordinary apparatus for manufacturing sulphuric acid I am enabled
to pass an excess of sulphurous acid through the chamber, and thus pre-
vent the nitrous acid from acting upon the lead of which the chamber
is constructed; by this means the chamber will be preserved, and will
last much longer than usual.
The second part of my improvements relates to a means of separating
arsenic from sulphuric acid, to effect which object I cause the
impure acid to percolate through a vessel containing a bed of pebbles
through which a stream of sulphuretted hydrogen is made to pass; the
sulphuretted hydrogen will be thereby decomposed, and the sulphur
will combine with the arsenic in the acid, and form what is called
yellow orpiment, which afterwards may be separated from the sul-
phuric acid by filtration, and the sulphuric acid will then be in a
proper state for evaporation.
Fig. 7, of Sheet II. is a side elevation of the apparatus whereby this
object is effected. The sulphuretted hydrogen is generated according to
any of the well-known methods in the vessel v, from whence it rises
into the chamber w, and from thence into a similar vessel w", both of
which are filled with stones or pebbles, and are supplied from above
with the impure acid. The acid, in descending through the vessels
w, w, comes in contact with the ascending current of sulphuretted
hydrogen, which, by combining with the arsenic contained in the acid,
becomes decomposed, and produces yellow orpiment, which by the
descent of the liquid acid will be washed out of the vessels w, and w,
into the trays y, from whence it may be removed at pleasure. The
uncombined gases will pass off through the pipe a, into the chimney,
and the purified acid from the trough y, of the vessel w, will fall into the

page_text: filter, made of sand or other suitable substance, from whence it may be
drawn out by the cock and concentrated in the ordinary manner.
Having now described my Invention of "Improvements in the Manu-
facture of Sulphuric acid," and the best means with which I am at
present acquainted for carrying the same into effect, I would observe,
in conclusion, that although in the foregoing Specification I have (in
order to render the nature and object of my improvements more clear)
described various matters which have been long known and in use for
similar purposes, yet I do not mean or intend to claim any such parts as
of my Invention; but that which I consider to be new in the above-
described process and apparatus, and therefore wish to claim as the
Invention secured to me by Letters Patent as aforesaid, is,-
First, heating the gases in their passage from the furnace to the con-
denser by means of the spare or waste heat of the furnace, or the spare
or waste heat of coke ovens or other furnaces, so that the said gases may
be made to combine with avidity and produce sulphuric acid.
Second, the use and application of nitro-sulphuric acid, or any other
similar or analogous compound, for absorbing sulphurous acid, and
acting upon it in the manner above set forth.
Third, separating arsenic from sulphuric acid by means of sulphu-
retted hydrogen, as above described.
In witness whereof, I, the said William Hunt, have hereunto set
my hand and seal, this Thirteenth day of February, in the year
of our Lord One thousand eight hundred and fifty-four.
Witness,
A. W. WHITEHOUSE,
Soapmaker, Wednesbury.
WILLIAM HUNT. (L.S.)