IMPROVEMENTS IN THE PURIFICATION OF COAL GAS
Year: 1865

page_text: LETTERS PATENT to Alexander Angus Croll, of Coleman Street, in the
City of London; Civil Engineer, for the Invention of "IMPROVEMENTS IN
THE PURIFICATION OF COAL GAS."
Sealed the 21st July 1865, and dated the 26th January 1865.
PROVISIONAL SPECIFICATION left by the said Alexander Angus Croll at
the Office of the Commissioners of Patents, with his Petition, on the
26th January 1865.
I, ALEXANDER ANGUS CROLL, of Coleman Street, in the City of London,
Civil Engineer, do hereby declare the nature of the said Invention for "Im-
PROVEMENTS IN THE PURIFICATION OF COAL GAS," to be as follows:-
The improvements relate to the use of sulphuric acid, wood sawdust, or
other suitable open or porous substance, and sulphate of lime, in the purifica-
tion of coal gas. I prefer that the sulphuric acid I employ be in a highly
concentrated and also in a highly heated state, say of a specific gravity of
about 1-700, and at a temperature of about 270 degrees Fahrenheit, and to
combine it with the wood sawdust in the proportion of say about 2 parts by
weight of the acid to 1 part by weight of the dry wood sawdust; and to the
combination obtained I add sulphate of lime in the proportion say of 1 part
by weight of the sulphate of lime to 2 parts by weight of the previous com-
bination. These conditions may, however, vary. In the purification of gas
the combined matters may be placed in vessels such as are commonly called

page_text: dry lime purifiers, or in other vessels adapted to effect the free action of the
matters on the gas. If desired, the combined sawdust, or other porous matter
and acid, may be placed in one vessel to act on the gas, and the sulphate of
lime, combined with sawdust or other suitable porous matter adapted to hold
the lime open, to act upon the gas in another vessel.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Alexander Angus Croll in the Great Seal Patent Office on
the 26th July 1865.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, ALEXANDER
ANGUS CROLL, of Coleman Street, in the City of London, Civil Engineer, send
greeting.
WHEREAS Her most Excellent Majesty Queen, Victoria, by Her Letters
Patent, bearing date the Twenty-sixth day of January, in the year of our Lord
One thousand eight hundred and sixty-five, in the twenty-eighth year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto me, the
said Alexander Angus Croll, Her special licence that I, the said Alexander Angus
Croll, my executors, administrators, and assigns, or such others as I, the said
Alexander Angus Croll, my executors, administrators, and assigns, should at
any time agree with, and no others, from time to time and at all times there-
after during the term therein expressed, should and lawfully might make,
nse, exercise, and vend, within the United Kingdom of Great Britain and
Ireland, the Channel Islands, and Isle of Man, an Invention for "IMPROVE-
MENTS IN THE PURIFICATION OF COAL GAS," upon the condition (amongst others)
that I, the said Alexander Angus Croll, 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 im-
mediately after the date of the said Letters Patent.
NOW KNOW. YE, that I, the said Alexander Angus Croll, 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:-
The improvements relate to the use of sulphuric acid, wood sawdust, or
other suitable open or porous, substance, and sulphate of lime in the purifica-
tion of coal gas.

page_text: In carrying out these improvements, I prefer that the sulphuric acid I
employ be in a highly concentrated and also in a highly heated state, say of
a specific gravity of about 1.700, and at a temperature of about 270 degrees
Fahrenheit, and to combine it with the wood sawdust in the proportion of
say about equal parts weight of the acid and of the dry wood sawdust; and
with the combination obtained I employ sulphate of lime in the proportion
say of 1 part by weight of the sulphate of lime to 2 parts by weight of the
previous combination. These conditions may however vary. In the purifi-
cation of gas the sawdust, or other suitable open porous matter employed, and
the acid should be placed in one purifying vessel, or one part of the purifying
vessel, and the sulphate of lime combined with sawdust or other porous matter
in another purifying vessel, or in another part of the purifying vessel, so that
the gas may be first acted upon by the sulphate of lime and sawdust. And
I prefer that the sawdust, or other porous matter thus separately combined
with sulphate of lime, be acidulated and saturated with ammonia by its pre-
vious use in the purification of gas. The quantity of sulphate of lime should
be in proportion to the quantity of carbonic acid gas present in the gas to be
purified, and I have found that when the gas is
it is purified from sulphuretted hydrogen it'
above stated, but when the sulphate of lime af
such purification it will be found that the pr
dust may be considerably lessened, and, in
lime and porous matter will have the effect of removing the whole of the
remaining ammonia without the use of other material.
purified from ammonia before
tires about the proportions
orous material are used after
tion of active acidulated saw-
me cases, that such sulphate of
Having thus described my Invention, I would have it understood that I do
not confine myself to the precise details given, as these may be varied; but
what I claim is the purification of gas by the use of sulphuric acid, wood saw-
dust, or other suitablo open porous substance, and sulphate of lime substantially
as described.
In witness whereof, I, the said Alexander Angus Croll, have hereunto
set my hand and seal, this Twenty-fifth day of July in the year of
our Lord One thousand eight hundred and sixty-five.
A. ANGUS CROLL. (L.S.)