IMPROVEMENTS IN PURIFYING GAS
Year: 1845

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, I, WILLIAM
CORMACK, of Dalgleish Street, Commercial Road, in the County of Middlesex,
Chemist, send greeting.
WHEREAS Her present most Excellent, Majesty Queen Victoria, by Her
Letters Patent under the Great Seal of Great Britain, bearing date at
Westminster, the Tenth day of April, in the eighth year of Her reign, did,
for, Herself, Her heirs and successors, give. and grant unto me,. the said
William Cormack, Her especial licence, full, power, sole privilege and authority,
that I, the said William Cormack, my exors, admors, and assigns,, or such
others as I, the said William Cormack, my exors, admors, or assigns, should
at any time agree with, and no others, from time to time and at all times
during the term of years therein expressed, should and lawfully might
make, use, exercise, and vend, within England, Wales,, and the Town
of Berwick-upon-Tweed, my. Invention of "IMPROVEMENTS IN PURIFYING GAS;"
in which said Letters Patent is contained a proviso,,that. I, the said William
Cormack, shall cause a particular description of the nature of my said Inven
tion, and in what manner the same. is, to be performed, to be inrolled in
Her said Majesty's High Court of Chancery within six calendar months
next and immediately after the date of the said in part recited Letters Patent,
as in and by the same, reference being thereunto had, will more fully and at
large appear.

page_text: NOW KNOW YE, that in compliance with the said proviso, 1, the said
William Cormack, do hereby declare that the nature of my said Invention, and
the manner in which the same is to be performed, are fully described and
ascertained in and by the following statement thereof (that is to say):-
In purifying gas by causing it to pass through liquids, as heretofore prac-
tised, the manufacturer has been prevented carrying the gas through any con-
siderable depth of the purifying liquor by the back pressure which would take
place in the retorts, for it is well known that at present the whole pressure
necessary for forcing the gas as it is generated through the purifying liquor
is caused by the generation of the gas, and therefore to encrease the depth of
the purifying liquids in the purifiers would encrease that pressure, which would
be highly injurious.
Now, the object of the first part of my Invention is to employ other means
than the pressure of the gas in the retort or generator to cause the gas to
pass into and through any desired-column of purifying liquid, thus relieving
the retorts or vessels in which the gas is generated from being pressed on or
influenced by the column of fluid through which the gas is forced for per-
forming the process of purification. In carrying out this part of my Inven-
tion the apparatus may be varied, but I prefer to employ two or more
gasometers, of a size depending on the extent of the works; and I so arrange
the inlet pipe to these gasometers that the cutting off the in-coming gas from
one of the gasometers shall open the passage into the other gasometer, and
then by causing the full gasometer to descend by pressure, I force the gas
through any desired depth of column of purifying. liquor, such depth, however,
not being so great as the depth the gasometer dips into the water; by this
means I am enabled to employ a considerable depth of purifying liquid, which
is very desirable, without in any way interfering with or adding to the pressure
in the retort or vessel in which the gas is generated; and I have found that a
column of two feet of liquid is a very good arrangement, but I do not confine
myself thereto, the object of my Invention being to receive the gas after it has
passed the hydraulic main into suitable apparatus, and then, by force of such
apparatus, to force the gas forward, so as to be enabled greatly to encrease the
column of fluid through which it shall be passed to purify it without adding to
the pressure in the retort by the encreased column of purifying liquid through
which the gas is passed, and in fact all the pressure that need be in the retort
will be that necessary for the gas passing through the hydraulic main; and
although I prefer gasometers, as above stated, alternately receiving and
forcing out the
it will be evident to the engineer that other apparatus may
be substituted therefor.
gas,

page_text: The second part of my Invention consists, of applying certain chemical solu-
tions, in the manner hereafter explained, for purifying gas. The materials so
employed by me may be used in the ordinary purifying vessels, such as are now
used in the wet lime purifiers, or they may be employed in vessels much
deeper, if the first part of my Invention be resorted to. First, I apply acetate
of lead, and by preference the brown acetate, for purifying coal gas from the
sulphuretted hydrogen and free ammonia, forming by their combination hydro-
sulphuret of lead, acetate of ammonia, and at the same time I produce caustic
ammonia, which caustic ammonia or part chemically combines with the free
sulphuretted bydrogen, forming hydrosulphuret of ammonia, and the other
part combining with the free carbonic acid, forming carbonate or subcarbonate
of ammonia. The sulphuret of lead so formed, as before described, precipitates
to the bottom of the purifying vessel as an insoluble compound, whilst the acetate
of ammonia, carbonate of ammonia, and caustic ammonia are held in solution
the caustic ammonia acting on both carbonic acid and sulphuretted hydrogen,
forming hydrosulphuret of ammonia and carbonate of ammonia, the carbonate
of ammonia remaining in solution, while the hydrosulphuret of ammonia is
decomposed, forming sulphuret of lead and caustic ammonia, which caustic
ammonia is continually presented to the sulphuretted hydrogen, carbonic acid,
and carbonic oxide, taking them up in solution as they come in contact; the
carbonate of ammonia so formed, as above described, from its volatile pro-
perties; part of it passes off with the gas to the next purifying vessel, where it
is taken up by liquid muriate of baryta or liquid muriate of lime, forming by
their combination muriate ammonia, and carbonate of baryta or carbonate of
lime; the carbonate of baryta or the carbonate of lime precipitated as an
insoluable compound, while the muriate of ammonia is held in solution; but it
should be understood that I do not claim the use of muriate of lime when
uncombined with the use of acetate of lead.
Having so far described the way in which chemical combination takes place
with acetate of lead, muriate of baryta, and muriate of line upon the impuri-
ties of the gas, I now describe the way in which I supply the acetate of lead,
muriate of baryta, and muriate of lime. First, I mix in some convenient
vessel brown acetate of lead with water, in the proportion of 112 lbs. weight of
acetate of lead to two hundred gallons of water, and so on in that proportion;
when dissolved it is ready for use. I then place it in the purifying vessel,
allowing the gas to pass through it, as in the usual way of wet lime purifica-
tion. When the mixture is fully saturated with the impurities. by applying
a test paper for the acetate of lead, the paper will turn black, thus shewing
that a fresh supply of the acetate of lead solution is required; I then draw off

page_text: the saturated products into a tank or reservoir, there to settle, when the sul-
phuret of lead will deposit to the bottom of the tank or reservoir; I draw off
the clear liquor, which is the acetate and carbonate of ammonia.. And in
order to separate the acetate of ammonia from the carbonate of ammonia, I
place them in a still, and add carbonate of lead in the proportion of. seventy
pounds weight to every hundredweight of acetate of lead used in the purifying
mixture. The carbonate of ammonia is then distilled over, and the acetic acid
combines with the lead, forming acetate of lead, which acetate of lead I return
back to the purifiers, so that the whole of the acetate of lead can be recovered,
or nearly so, to be worked over and over again.
I now describe the way I supply the muriate of baryta or muriate of lime
or acetate of lime to the second purifying vessel, or third. I dissolve one hun
dred and twelve pounds of muriate of baryta into one hundred gallons of water,
and so on in that proportion; the carbonate of ammonia formed in the acetate
of lead purifier escaping with gas into the muriate of baryta purifier is taken
up the instant they come in contact, forming carbonate of baryta and muriate
ammonia; the muriate ammonia I evaporate to crystals; as in the usual way;
the carbonate of baryta I re-dissolve by muriatic acid, forming the muriate of
baryta, to be used over again for the freeing of the carbonate ammonia...In
order to ascertain when the muriate of baryta is saturated; I withdraw a small
quantity from the purifier into a glass; and drop a few drops of crude ammo-
iiacal liquor into it; if not saturated, it will throw down a white precipitate,
and if it remain clear it is saturated, and a fresh charge is required. "In-using
the muriate of lime instead of the muriate of baryta, I add one hundred-and
twelve pounds weight of muriate of lime to fifty gallons of water; the gas
passing through this solution is freed from the carbonate ammonia, forming
carbonate of lime and muriate of ammonia, which carbonate of lime I dissolve
with muriatic acid, forming muriate of lime, to be applied over again. When
acetate of lime is employed, it is used at the rate of one pound weight of acetate
of line to a gallon of water; the acetate of lime will be decomposed by the
carbonate of ammonia, forming acetate of ammonia and carbonate of lime; and
to separate the acetic acid from the acetate of ammónia I apply caustic lime,
as well understood, thus producing acetate of lime; to be again used in the
second purifier, and caustic ammonia; and I separate the caustic ammonia from
the acetate of lime by distillation.
.
I now describe the way in which I reconvert or get back the acetate of lead
from the sulphuret of lead. First, I treat the sulphuret of lead with carbonate
of lime, charcoal, or small coal, and apply a red heat to the mixture in a
ieverberatory furnace, as is well understood, by which means the carbon of the

page_text: coal, lime, or charcoal combines with the lead, forming carbonate of lead, and
the sulphur.is: driven off..
Another method of applying the acetate of lead is, to the crude ammo-
niacal liquor,..such as it comes from the condensing mains. For every
gallon of the crude liquor I add seven ounces of the acctate of lead, which
immediately throws down the sulphuretted hydrogen; I then draw off the
clear liquor so freed from sulphur, and apply it to the purifier instead of
the mixture of acetate of lead, as before described, it containing in solution a
subcarbonate of ammonia and caustic ammonia; and from the affinity of the
caustic ammonia to the sulphuretted hydrogen and carbonic acid there will be
formed hydrosulphuret and carbonate of ammonia; and when fully saturated,
I draw off and charge afresh, taking care to decompose the whole of the sulphur
by the acetate of lead in the way before described; and the sulphuret of lead I
convert into acetate of lead, as before described.
Another method of purification coal gas, according to my Invention, is, by
the use of acetate of iron, forming by this combination sulphuret of iron and
acetate of ammonia, which acetate of ammonia when so formed I treat with
sulphate of iron, forming sulphate of ammonia and acetate of iron, to be used
again in the purifier; and in using acetate of iron, I dissolve the same at the
rate of one hundred pounds to one hundred gallons of water, and I ascertain
when it is saturated when a quantity withdrawn remains clear when crude
ammoniacal water is dropped in.
Another method of purifying coal gas is by the use of acetate of baryta, which
I dissolve at the rate of seventy-five pounds to one hundred and twenty gallons
of water, and I test the liquor of the purifier by crude ammoniacal liquor, as
before explained.
Having thus described the nature of my Invention, and the manner of per-
forming the same, I would wish it to be understood that what I claim is, first,
the causing gas to pass through greater columns of purifying liquor, by appa-
ratus so arranged as not to encrease the pressure on the retort or vessel wherein
the gas is generated by the encrease of column of the liquor; and, secondly, I
claim the application of the acetate of lead, the acetate of iron, and the acetate
of baryta, and also the use of muriate of baryta, and muriate of lime, and
acetate of lime, as herein described.
In witness whereof, I, the said William Cormack, have hereunto set my
hand and seal, this Tenth day of October, in the year of our Lord
One thousand eight hundred and forty-five.
WCORMACK. (L.S.)

page_text: AND BE IT REMEMBERED, that on the Tenth day of October, in the
year of our Lord 1845, the aforesaid William Cormack came before our said
Lady the Queen in Her Chancery, and acknowledged the Specification afore-
said, and all and every thing therein contained and specified, in form above
written. And also the Specification aforesaid was stamped according to the
tenor of the Statute made for that
purpose.
Enrolled the Tenth day of October, in the year of our Lord One thousand