IMPROVEMENTS IN THE PURIFICATION OF COAL GAS
Year: 1859

page_text: LETTERS PATENT to John Leigh, of the City of Manchester, in the
County of Lancaster, Surgeon, for the Invention of "IMPROVEMENTS IN
THE PURIFICATION OF COAL GAS."
Sealed the 10th May 1859, and dated the 5th March 1859.
PROVISIONAL SPECIFICATION left by the said John Leigh at the
Office of the Commissioners of Patents, with his Petition, on the
5th March 1859.
I, JOHN LEIGH, of the City of Manchester, in the County of Lancaster,
Surgeon, do hereby declare the nature of the said Invention for "IMPROVE-
MENTS IN THE PURIFICATION OF COAL GAS," to be as follows:-
My Invention consists in the application of gas water, commonly called
"ammonia water," which has been treated with or mixed with lime or any
other alkali or alkaline earth, with the view of removing the carbonic acid
together with any other acids with which such lime, alkali, or alkaline earths
may combine from the ammonia water or gas water, and then in passing the
gas through the gas water, which has been so treated, in suitable vessels in
order to remove from the gas not only the salts of ammonia existing therein,
but also the carbonic acid, sulphuretted hydrogen, hydrocyanic acid, sulpho-
cyanic acid, &c., which may exist also in the impure gas.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said John Leigh, in the Great Seal Patent Office on the
5th September 1859.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JOHN
LEIGH, of the City of Manchester, in the County of Lancaster, Surgeon,
send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Fifth day of March, in the year of our Lord
One thousand eight hundred and fifty-nine, in the twenty-second year of
Her reign, did, for Herself, Her heirs and successors, give and grant unto
me, the said John Leigh, Her special licence that I, the said John
Leigh, my executors, administrators, and assigns, or such others as I,
the said John Leigh, 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 PURIFICATION OF COAL GAS," upon the condition (amongst
others) that I, the said John Leigh, 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 John Leigh, do hereby declare
the nature of my said Invention, and the manner in which the same is to be
performed, to be particularly described and ascertained in and by the following
statement (that is to say):-
My Invention consists in the application of causticised or partially causticised
gas water or ammonia water, that is to say, gas water or ammonia water
which has been treated with or mixed with lime or any other alkaline earth,
or alkali, with the view. of removing the carbonic acid, together with any other
acids with which such lime or alkaline earths or alkalies may combine in the
gas water to the purification of coal. gas or caunel gas, which I effect by
passing the gas through the gas water, which has been so treated, in suitable
vessels in order to remove from the gas not only the salts of ammonia existing
therein, but also the carbonic acid, sulphuretted hydrogen, sulphocyanic acid,
hydrocyanic acid, &c., which may exist also in the impure gas.

page_text: For the causticising of the gas water or ammonia water, I prefer to use
lime which may be mixed with the gas water in proportions varying with the
strength or specific gravity of the ammonia water acted upon. For ammonia
water of the specific gravity of six degrees or seven degrees of Twaddell's
hydrometer, I find about four hundred pounds weight of dry lime a suitable
quantity for the causticising of eight hundred gallons of ammonia water. I
first slake or slack the lime, and then add it to the ammonia water, keeping
it mixed therewith by constant agitation for a considerable time. When I
find by the reduced specific gravity, that is to say, when the gravity of the
ammonia water is reduced to one, two, or three degrees of Twaddell's hydro-
meter, I allow the lime to settle, and draw off the causticised ammonia
water into a vessel, from which it is pumped into a series of washing vessels
being carried through pipes and impinging from a jet pipe on a flat plate at
the upper part of each washing vessel falling thence in spray or in showers
through the washing vessel which contains a number of shelves covered with
brickbats or other material exposing extent of surface. The gas entering at
the lower part of each washer being brought into contact in the washer with
the causticised ammonia water imparts to it not only the salts of ammonia
which it contains, but also the carbonic acid, sulphuretted hydrogen, sulpho-
cyanic, and hydrocyanic acid or other acids which may exist in the gas as
impurities. As some portion of the salts of ammonia may be carried forward
beyond the washing vessels mechanically by the velocity of the gas, these
may be removed by passing the gas terminally through one or more
purifiers containing layers of any one of the numerous substances capable of
removing the salts of ammonia, or otherwise a few layers of lime.
the ammonia water intended for
liquor causticised is received, and
The washer or vessel in which the
And in order that the process may be clearly understood, I have shewn in
the accompanying Sheet of Drawings a suitable apparatus for the purpose,
though other kinds of apparatus may be used. Fig. 1 is a vertical section,
and Fig. 2, a sectional plan of the apparatus which I have found very efficient.
a represents a vessel in which is placed
causticising; b, a cistern into which the
from which the force-pump c is supplied.
gas is purified or freed from its salts or ammonia or other impurities above
specified is shewn at d, which may be made of any convenient size or shape.
The ammonia water is supplied at the upper part of the vessel by the
injection pipe e connected to the force-pump, and spread about by the dis-
persing plate f. At certain intervals in the interior of the vessel are grids g,
each of which is covered with materials to retard the return of the ammonia
water, and thus afford time for it to mix with and purify the gas, the said

page_text: materials consisting of bricks, ashes, or other suitable substance. The inlet
pipe for the gas is shewn at h, and the outlet pipes at i and k, the water being
discharged through the cistern l, and the syphon m.
Having thus fully described the nature of my said Invention, and the
manner in which the same is to be performed, I desire it to be distinctly
understood that I do not claim any particular kind of apparatus for carrying
.out my said Invention, nor the use of any particular substance or material,
but I claim the use of causticised or partially causticised gas water or ammonia
water for the purification of coal or cannel gas, as herein described.
In witness whereof, I, the said John Leigh, have hereunto set my
hand and seal, this Third day of September, in the year of our Lord
One thousand eight hundred and fifty-nine.
Signed, sealed, and delivered by the within
named John Leigh in the presence of
E. J. HUGHES, Patent Agent,
Manchester.
JOHN LEIGH. (L.s.)