IMPROVEMENTS IN THE PURIFICATION OF GAS
Year: 1854

page_text: Sealed the 21st April 1854, and dated the 20th February 1854.
PROVISIONAL SPECIFICATION left by the said John Chisholm at the
Office of the Commissioners of Patents, with his Petition, on the 20th
February 1854.
I, JOHN CHISHOLM, do hereby declare the nature of the said Invention for
"IMPROVEMENTS IN THE PURIFICATION OF GAS" to be as follows:-
I have discovered that certain earthy compounds exist which possess the
power of purifying gas. My present object is to patent these, and to claim
their use for such purpose.
First, the silicious earthy matter containing oxide of iron, oxide of man-
ganese, &c., found under bogs and in alluvial deposits.
Second, the ferruginous gravel which overlies and is intermingled with the
chalk formation of this island.
"Third, the ferruginous clay or loom of the alluvial formation.

page_text: Fourth, the phosphate and subphosphate of iron which exists in the tertiary
formation, and all of which I propose to use combined with hydrate of lime,
or the mixed hydrate of lime and magnesia obtained by calcining magnesian
limestone, and with these mixtures I propose to purify gas from sulphuretted
hydrogen, and in some measure from ammonia and carbonic acid.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said John Chisholm in the Great Seal Patent Office on the
16th August 1854.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JOHN
CHISHOLM, of Holloway, in the County of Middlesex, Chemist, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Twentieth day of February, in the year of our Lord
One thousand eight hundred and fifty-four, in the seventeenth year of
Her reign, did, for Herself, Her heirs and successors, give and grant unto
me, the said John Chisholm, Ier special licence that I, the said John
Chisholm, my executors, administrators, and assigns, or such others as I, the
said John Chisholm, my executors, administrators, and assigns, should at any
tine 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 PURIFICATION OF GAS," upon the condition (amongst others) that I, the
said John Chisholm, 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 imme-
diately after the date of the said Letters Patent.
NOW KNOW YE, that I, the said John Chisholm, do hereby declare the
nature of the said Invention, and in what manner the same is to be per-
formed, to be particularly described and ascertained in and by the following
statement:-
My Invention consists in combining or mixing together the peculiar red
earthy or ochry looking substances found mingled with peat, and the subsoil
of peat, with hydrate of lime, or the mixed hydrates of lime and magnesia

page_text: obtained from magnecian limestone, and this combination or mixture I then
introduce into the vessel known to gasmakers by the term dry-gas purifier,
and into this vessel and through this mixture the foul gas is then passed until
it is rendered pure, such purity being ascertained by the application of the
tests usually employed by makers of gas for that purpose. The red earthy or
ochry substance above alluded to is composed chiefly of the oxides and salts of
iron and manganese, and it is principally to these metallic matters that the
purifying agency of the compounds is due; therefore the greater the quantity.
of these oxides this earthy matter contains, the better it is adapted for the
purpose for which I use it; and although the exact proportion of lime to be.
added is not material, yet the greater the amount of metallic matters there
may be contained in the red or ochry earthy matters aforesaid, the more lime
or lime and magnesia must be used. I prefer to use for every three parts by
weight of metallic matters in this earthy matter one part of line by weight.
Instead of the above red earthy matter, I sometimes employ in the same way
and proportion the fine red sandy gravel so general around London, in the
neighbourhood of chalk beds, or the red clay which is so common around
Rugby and other districts, or the phosphate or subphosphate of iron known
by these names to all geologists, and common in many boggy districts. All
these or any of them I use precisely in the way or combination described with
respect to red earthy peat matters, herein-before alluded to; and I would add,
that when these substances or mixtures, or any of them, have ceased to purify
the gas from sulphuretted hydrogen and other impurities, their powers may
be again in part or altogether renewed or restored by passing or forcing through
them a current of air, or even by merely exposing them to the air, after which
they may be used over and over again or many times in succession.
Having now described the nature of my Invention of "Improvements in the
Purification of Gas," I will now state that I claim,-
Firstly, the use of the silicious earthy matter herein described containing
oxides of iron and oxides of manganese, and found under bogs and in
alluvial deposits, and treated in the manner herein-before described for purify-
ing gas.
Secondly, I claim the use of ferruginous gravel which overlies and is inter-
mingled with chalk formations, treated as herein-before described for purifying
gas.
Thirdly, I claim the use of the ferruginous clay or loam of the alluvial
formation, treated as herein-before described for purifying gas.

page_text: And, lastly, I claim the use of the phosphate and subphosphate of iron
which exists in the tertiary formation, treated in the mode and manner herein-
before described for purifying gas.
In witness whereof, I, the said John Chisholm, have hereunto affixed my
hand and seal, this Fifteenth day of August, in the year of our Lord
One thousand eight hundred and fifty-four.
Witness,
JOHN GEDGE,
Patent Agent,
4, Wellington Street South,
Strand, London.
JNO. CHISHOLM. (L.S.)