IMPROVEMENTS IN THE PREPARATION OF MATERIALS TO BE USED IN THE PURIFICATION OF GAS FOR ILLUMINATION
Year: 1864

page_text: LETTERS PATENT to Alexander Angus Croll, of Coleman Street, in the
City of London, Engineer, for the Invention of "IMPROVEMENTS IN THE
PREPARATION OF MATERIALS TO BE USED IN THE PURIFICATION OF GAS FOR
ILLUMINATION."
Sealed the 12th May 1865, and dated the 18th November 1864.
PROVISIONAL SPECIFICATION left by the said Alexander Angus Croll
at the Office of the Commissioners of Patents, with his Petition, on the
18th November 1864.
I, ALEXANDER ANGUS CROLL, of Coleman Street, in the City of London,
Engineer, do hereby declare the nature of the said Invention. for "IMPROVE-
MENTS IN THE PREPARATION OF MATERIALS TO BE USED IN THE PURIFICATION OF
GAS FOR ILLUMINATION," to be as follows:-
In the preparation of materials to be used in the purification of gas for
illumination, I mix chloride or sulphate of zinc, or chloride or sulphate of man-
ganese, or chloride or sulphate of iron with lime, by preference unslacked and
in proportions varying with the amount of ammonia in relation to the carbonic
acid, or sulphuretted hydrogen gas required to be absorbed in the purification
of the gas.
I have obtained good results by the use of lime slacked or unslacked in the
proportions of 1 part thereof to 5 parts of the salt employed, or as a carbonate
in a finely divided state or as a chloride, or as a sulphate, in the proportions
of 1 part thereof to 3 parts of the salt employed, but these proportions may

page_text: vary very materially, and when the mixture has been fully effected, I combine
it with sawdust or other porous matter adapted to hold such mixture open, and
admit of its freely acting upon gas passed through it in purifying apparatus
or vessels.
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 18th May 1865.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, ALEX-
ANDER ANGUS CROLL, of Coleman Street, in the City of London, Engineer,
send greeting.
WHEREAS. Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Eighteenth day of November, in the year of our Lord
One thousand eight hundred and sixty-four, 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 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 PREPARATION OF MATERIALS TO BE USED
IN THE PURIFICATION OF GAS FOR ILLUMINATION," upon the condition (amongst
others) that I, the said Alexander Angus Croll, my executors or administra-
tors, 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 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 :-
'My improvements relate to the employment of chloride or sulphate of zinc,
or chloride or sulphate of manganese, or chloride or sulphate of iron and lime

page_text: combined with sawdust or other porous matter, adapted to hold such mixture
open, and admit of the free action thereon of the gas in the purification of
gas for purposes of illumination.
such
In carrying out my improvements when employing sulphate of zinc, I mix
such salt of zinc with the lime by preference in the state of quick or unslacked
flare, burned chalk, lime in a powdered or finely divided state, and in the pro-
portion of five parts or thereabouts of the cystallized salt to one part or there-
about of the lime. And I incorporate these matters by spreading them in
alternate layers, and then when the lime is slacked thoroughly, mixing them
up with a free access of air. The composition obtained I then mix with wood
sawdust, or other porous material adapted to hold it open, and admit of the gas
freely acting thereon. And I then place the mixture obtained in purifying
apparatus through which the gas to be purified is caused to pass, as is well
undertsood when using other matters in the purification of gas for illumi-
nation by which such gas will become purified from sulphuretted hydrogen,
ammonia, and other impurities. When from use these purifying matters have
become spent so as to cease to remove sulphuretted hydrogen from the gas
passed through them, they may be revivified by free exposure of tem to
the atmosphere when they may be again applied to the purification of gas as
before.
It will frequently be found that these purifying matters will by use lose
their power of removing sulphide of ammonium (a condition which is easily
ascertained by its power of blackening a piece of paper immersed in it which
has previously been moistened with sulphate of iron) although they may still
be capable of acting on carbonate of ammonia. In this case I sprinkle over
the matters during the revivifying a portion of the metallic salt used in the
preparation of them in a strong solution, or in the state of crystallization, and
I continue such application until carbonate of ammonia ceases to be capable
of being readily removed, a condition which may be ascertained by the action
of the matters on turmeric paper. A like treatment will be found applicable
to the sulphate of iron, or to the sulphate or chloride of manganese, but with
the latter salt only one half of the quantity of lime may be sufficient. In using
the chlorides of iron or zinc, I take solutions of them containing about equal
weights (as readily ascertained by ordinary analysis) of anhydrous chlorides
and water, and I add thereto about one-fifth of their weight of the lime, and
when the solution contains more water I proportionately reduce the lime, I
then dry the solution to a convenient state for use. In the case of the use of
the chlorides in the preparations, care must be taken to avoid a too free

page_text: exposure to atmospheric influênce on account of their deliquescent tendency by
which a too moist condition might be obtained which would interfere with the
free action of the gas through the preparations.
All these proportions will however vary materially with the amount of
impurities contained in the gas to be purified..
In carrying out my improvements I find that the best results are obtained
by passing the gas first through a' preparation obtained by the use of the
sulphate of zinc or chloride of manganese .as described, and then through'a
preparation obtained' by the use of the sulphate of iron as described.
Having thus described my improvements I would have it 'understood that'
what I claim is the employment of chloride or sulphate of zinc; or chloride or
sulphate of manganese, or chloride or sulphate of iron and lime mixed with
wood sawdust, or other suitable open porous matter in the purification of gas
for illumination in manner substantially as explained.
In witness whereof, I, the said Alexander Angus Croll, have hereunto
set my hand and seal, this Eighteenth day of May, in the year of
our Lord One thousand eight hundred and sixty-five.