IM- PROVEMENTS IN THE TREATMENT OF SULPHUROUS GASES, AND IN THE MEANS EMPLOYED THEREFOR
Year: 1879

page_text: LETTERS PATENT to Alfred Henry Allen, F.C.S., Analytical Chemist, of
Surrey Street, Sheffield, in the County of York, for the Invention of "IM-
PROVEMENTS IN THE TREATMENT OF SULPHUROUS GASES, AND IN THE
MEANS EMPLOYED THEREFOR."
Sealed the 29th July 1879, in pursuance of an Order of the Lord Chancellor, and
dated the 16th Try 1970
PROVISIONAL SPECIFICATION left by the said Alfred Henry Allen at the
Office of the Commissioners of Patents on the 16th January 1879.
ALFRED HENRY ALLEN, F.C.S., Analytical Chemist, of Surrey Street, Sheffield,
in the County of York. "IMPROVEMENTS IN THE TREATMENT OF SULPHUROUS
GASES, AND THE MEANS EMPLOYED THEREFOR."
These improvements consist in the absorption of sulphurous acid, and its separa-
tion from nitrogen when these gases are obtained together, as for instance, in the
burning of minerals or other substances containing sulphur, by passing over them a
current of air, or by blowing air through molten sulphides, as in Hollway's
process.
The gases preferably freed from impurities mechanically carried over with them
are led into towers, chambers, or other suitablo vessels filled with charcoal or
similar porous substance which will absorb and retain the sulphurous acid, and
allow the nitrogen to escape.
In order to free the gases from impurities, they may be caused to impinge on a
liquid surface, or be otherwise brought in contact with a liquid; by employing
for this purpose concentrated sulphuric acid, this object will be attained, and any
moisture present in the sulphurous acid will be removed.
The sulphurous acid is afterwards obtained from the absorbent by exhaustion, by

page_text: heat, or in other ways, and being thus practically free from nitrogen, it can moro
readily be liquified by compression or converted into sulphuric acid than is possible
in the presence of a large quantity of nitrogon. If the current of the mixed gases
be produced continuously, it is advisable to use two or more sets of absorbing
towers or chambers, so that while one set is in uso for absorption, the condensed
sulphurous acid may be extracted from the material employed in a previous
operation.
The sulphurous acid having been oxtracted from the charcoal or other absorbent
employed, will be ready for another operation, and may thus be used many times
in succession.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Alfred Henry Allen in the Great Seal Patent Office on the 29th
July 1879.
ALFRED HENRY ALLEN, F.C.S., Analytical Chemist, of Surrey Street, Sheffield,
in the County of York. "IMPROVEMENTS IN THE TREATMENT OF SULPHUROUS
GASES, AND IN THE MEANS EMPLOYED THEREFOR.'
"
My Invention consists in the means employed for absorbing sulphurous acid and
effecting a partial or completo separation of it from nitrogen, when these gases aro
obtained together, either as part or the whole of a gaseous mixture, as for instance,
in the burning of minerals or other substances containing sulphur, by passing over
them a current of air, or by blowing air through molten sulphides, as is described in
the Specification of a Patent granted to John Hollway, No. 1131, A.D. 1878.
In carrying out my Invention, I prefer first of all to free them from all dust,
smoke, and other suspended matter, by passing them through suitable chambers,
pipes, or other known arrangements adapted for such purposes, or by causing them
to impinge on the surface, or otherwise be brought into contact with a liquid.
I prefer next to purify the gases thoroughly from all trace of moisture in cases in
which any is present, and I do that by causing them to pass through pipes, towers,
chambers, or other arrangements containing coke, pebbles, bricks, or similar
materials saturated with concentrated sulphuric acid or other powerful dehydrating
agent, or I use other known means of bringing the gases in contact with the
dehydrating agent.
Having purified the gases from suspended particles and moisture by the above
described or other suitable means, I cause them to enter towers, chambers, pipes, or
other suitable vessels containing charcoal or similar porous substance which will
absorb and retain the sulphurous acid, and allow all or the greater part of the
nitrogen to escape.
As an absorbing substance, I prefer to use fragments of wood charcoal, so packed
as to allow free circulation of the gases through the apparatus, but I do not limit
myself to the use of wood charcoal as an absorbent body.
I prefer to prepare the charcoal for use as an absorbent by heating it to redness,
and cooling it in a current of nitrogen.
When the gases which pass through the absorbing arrangement give evidence
that the charcoal is nearly saturated with sulphurous acid, as is known by the
powerful smell of the evolved gases, and by their power of decolorizing Condy's
purple disinfecting fluid, I arrest the passage of the gases, and by suitable valves,
cocks, or similar means I close the absorbing apparatus completely.
I next proceed to extract the sulphurous acid contained in the charcoal or similar
absorbing substance, and this I prefer to do by applying a vacuum pump, which
causes the gasification of a portion of the condensed sulphurous acid gas. I do not
limit myself to the use of a vacuum only for extracting the sulphurous acid, but in
some cases I heat the absorbing apparatus to a temperature of 300 or 400 degrees
centigrade, and by preference I employ the combined action of heat and a vacuum,
and I construct the absorbing apparatus in such a manner and of such materials
that I may be able to apply heat in the manner stated.
Having obtained the sulphurous acid again in a gascous state, it may be em-
ployed for known purposes, such as the manufacture of sulphuric acid and of
metallic sulphites, or condensed by pressure to a liquid state.
The sulphurous acid having been extracted from the charcoal, the latter when
cold may be employed to absorb a fresh quantity of sulphurous acid gas from a
mixture containing it, and may thus be used many times in succession.
I prefer to employ two or more sets of absorbing arrangements, so that one set
while in use absorbing the sulphurous acid from a gaseous mixture, the operation
of extracting the condensed sulphurous acid may be going on in another, while a

page_text: third may be cooling down preparatory to being used for treating a fresh quantity
of sulphurous gases.
Having now described the nature of my said Invention, together with the
manner of performing the same, I would wish it to be particularly understood in
conclusion, that I lay no claim to,-
First. The production of the sulphurous gases.
Second. The means hereinbefore described for obtaining the sulphurous gases free
from suspended matter and moisture, and,
Third. The application of the sulphurous acid recovered from the charcoal to the
manufacture of sulphuric acid, metallic sulphites, liquid sulphurous acid, or any
other purpose, but what I do claim as new and as of my Invention is,―
First. The treatment of sulphurous gases produced in metallurgical or other
manufacturing operations, by passing them through an arrangement containing
charcoal or similar porous substance, whereby the sulphurous acid is absorbed and
retained by the charcoal, while the nitrogen and other gases remain partly or
entirely in the gascous state, as herein substantially described and set forth, and,
Second. The treatment of the charcoal or similar porous substanco containing
condensed sulphurous acid by a vacuum or heat, or both means combined, in order
to re-obtain the sulphurous acid in a gaseous state in the manner as herein before
substantially described and set forth.
In witness whereof, I, the said Alfred Henry Allen, have hereunto set my
hand and seal, this Twenty-second day of July, in the year of our Lord One
thousand eight hundred and seventy nine.
ALFRED HENRY ALLEN. (L.B.)