Year: 1853

page_text: I already use chloride
charcoal naturally containing an alkali combined with an acid, or a
metal similarly combined, as a peat strongly impregnated with sul-
phuric acid; and iron can be used with similar effect, or it may
be combined with chlorine or calcium; such peat will decompose
ammonia in a natural state, and should be dried and ground
when so used in the processes of purification. The peat or peat
charcoal containing iron and sulphuric acid, after it has deprived the
gas of its ammonia, may be removed from the purifyer, the sulphate
of ammonia washed out of it and sold, either as a sulphate, or manu-
factured into any of the salts of ammonia; this of course in all cases
when not combined with the manure; and the peat, by being exposed to
the atmosphere, will have its iron converted into a peroxide, and may
be used in the gas. purifyer for decomposing the sulphuretted hydrogen.
Or the peat containing the sulphuric acid and iron may be burned in
an open furnace, and the ashes added to other peat or charcoal, for the
purpose of depriving gas of its sulphuretted hydrogen; the ashes I
propose to use alone for this purpose also. Peat containing iron in
any form I intend to use in a similar manner.
of sodium and superphosphate of lime, mixed with charcoal, for
decomposing ammonia contained in gas. I propose to use chloride of
sódium, mixed with peat or peat charcoal, or other charcoals alone, for
taking up the ammonia; in such case I intend using a peat, rich in
carbon, and containing little or no iron, or sulphuric acid, or chlorine
and calcium. I also intend using peat or peat charcoal containing
sulphuric acid and iron, or chlorine of calcium, for decomposing
the ammonia contained in the ammoniacal liquor, and converting it
into a sulphate or chloride of ammonium. Peat containing the
peroxide of iron, as used by me for depriving gas of its sulphuretted
hydrogen, will do so without being converted into charcoal, but I
prefer it in a state of charcoal; in either case, if the ashes remaining
in the open furnace after burning the peat containing sulphuric
acid and iron be added, it will improve its purifying properties. In
the purifying vessels in a gas purifying chamber there are a series of
perforated trays, upon which the peat or peat charcoal, either alone,
or with the addition of any of the chemicals I use, is placed, so that the
gas may pass through without requiring pressure; the upper tray, either

page_text: in the sulphuretted hydrogen purifier, or in that for taking up the
ammonia, may be charged with a hydrate of lime to take up any car-
bonic acid contained in the gas, such lime being now used for that pur
pose, or a seperate purifier may be used for the lime process, and which
may be called the carbonic acid purifier. The lime will take up the
carbonic acid, if mixed with the peat or charcoal; I prefer to use it
seperate.
In improving a peat containing little iron and sulphuric acid I
prefer to add sulphate of iron dissolved in twenty times its weight of
water, and saturate the peat with the solution; this peat may be used
alone, or converted into charcoal.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said William Chisholm in the Great Seal Patent
Office, on the 21st November 1853.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I,
WILLIAM 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 Twenty-first day of May, in the year
of our Lord One thousand eight hundred and fifty-three, in the six-
teenth year of Her reign, did, for Herself, Her heirs and successors, give
and grant unto me, the said William Chisholm, Her special licence
that I, the said William, Chisholm, my executors, administrators, and
assigns, or such others as I, the said William Chisholm, 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 FOR THE PURPOSES OF ILLUMINATING AND
HEATING, AND OBTAINING, BY THE INGREDIENTS USED THEREPOR, MANURES,
SALTS OF AMMONIA, AND SULPHUR," upon the condition (amongst others)
that I, the said William Chisholm, by an instrument in writing

page_text: 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.
..
1.
*NOW KNOW YE, that I, the said William Chisholm, 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 änd
by the following statement thereof:
'
{:
My Invention consists, firstly, in the purification of coal gas by peats
containing substances with which they are found associated in nature,
or peats to which, when deficient in such substances, they are artificially
supplied. Secondly, in the obtaining salts of ammonia from peats
which have been so used for the purification of gas, and, from the
ordinary ammoniacal liquor of gas works by the use of similar peats.
Thirdly, in the production of a manure. by mixing certain substances
with some of the peats so used for the purification of gas. Fourthly,
in the obtaining of sulphur as a residium in a certain part of the
process.
There are to be found in various localities in the United Kingdom
peats naturally combined with mineral substances capable of purifying
illuminating gas; I avail myself of the use of such peats in my opera-
tion. I use; for instance, a peat containing a peroxide of iron för
depriving gas of its sulphuretted hydrogen, and another peat containing
a sulphate of iron, or a sulphate of lime, for depriving gas of its
ammonia. Where a peroxide of iron peat is not easily obtained
I treat a sulphate of iron peat in a manner hereafter to be described,
so as to bring the iron to the state of peroxide.
It is desirable to have the peat saturated with as large a proportion
of the mineral substances as will not entail the necessity of too
frequently opening the purifying vessels, but not so much as to cause
mich resistance to the free passage of the gas through it, thereby
causing a back pressure upon the retort; about 40 per cent., by weight,
may be considered the maximum, but poor mineral peats may be
brought up to any given standard by a process I will hereafter describe.
The dry lime purifiers are vessels too well known at all gas works to

page_text: require any description; such vessels Imake use of in my operations;
and they should never be fewer than 4 in number, although 3 only;
are required to be in operation at one time; let us suppose there are 4,1
and numbered 1,2,3, and 4: I fill No.1, with sulphate, of iron peat,/
number: 2; with peroxide of, iron peat, and No. 13, is charged in the
usual way with a hydrate of lime; this latter vessel is connected with
the gasométer or gas-holder; the gas is made first to pass through,
No. 1, where the ammonia will be arrested by the sulphuric acid;
contained in the sulphate. of iron, forming a sulphate of ammonia;
it: then passes through No 2, where its sulphuretted hydrogen is
decomposed by the peroxide. of iron, sulphur being deposited in its
progress. In No. 3, the carbonic acid is fixed by the hydrate of lime,
forming a carbonate of lime; the gas. now passes on to, the gas-holder;;
the time that the. material will continue to purify gas will depend?
upon a variety of circumstances, such as the quality of the coal, the
size of, the purifying vessels, and the quantity of gas passed, through,
them; the vessels may be such a size as not to require charging fort
several months; the application of a. test will at once show when
the material ceases to purify gas; for instance, if the gas which has
passed through No. 1, stains turmeric paper brown; it shews that
ammonia.is escaping, and the vessel must be emptied, and re-charged;
if paper moistened. with.a solution of acetate of lead is stained; black-
upon being exposed to the gas after it has passed through--No. 2, it
proves that sulphuretted hydrogen; is present; the contents: should be..
removed and freshly charged, or the contents of the vessel may remain,
provided they have been exposed to the air, or a stream of atmospheric
air has been passed through; if moistened with, steam, the reconversion +
of the protosulphuret into a peroxide of iron will be promoted. I have,::
however, found in practice, that it is better to remove the material, and
use a fresh charge. If the gas from No. 3, turns lime water milky, it
indicates the presence of carbonic acid; the carbonate of lime should
in this case be removed, and the vessel charged with. a fresh supply of!
hydrate of lime. In a gas.works in full operation the gas continues
to flow from the retorts through the purifiers to the gas-holder without>
interruption, night and day; there can, therefore, be no shutting off the..
gas while you are emptying and replenishing the contents of a purifying

page_text: vessel; hence the necessity of No. 4, a spare vessel; we shall suppose
that No. 1, is the first vessel which shows symptoms of being saturated
by turning brown the turmeric paper. Immediately charge No. 4,
with a sulphate of iron peat, and turn the gas from No. 1, to No. 4;
the vessels change places, the gas passing first through No. 4, then on
to No. 2, then to No. 3, and, lastly, into the gas-holder; the contents
of No. 1, are removed, and the sulphate of ammonia washed out; the
peat is then spread upon the floor of a building which has a roof to
protect it from the rain, but open in other respects to the atmosphere;
here it requires to be turned over frequently, so that the superabundant
moisture may evaporated, and the iron become peroxidized. We will
now suppose that No. 2, requires to be changed, the gas having begun
to blacken the acetate of lead paper. We refill No. 1, either with a
fresh peroxide peat, or with the peat that was originally contained in
No. 1, from which the sulphate of ammonia has been washed out, and
which has been peroxidized and dried by exposure to the atmosphere;
the gas is then shut off from No. 2, and turned on No. 1, and passes
through, first, No. 4, then No. 1, and, lastly, No. 3. The same process
of changing vessels takes place when No. 3, becomes foul, that is,
when it ceases to take up carbonic acid; by having four purifying
vessels there will always be an empty one ready to substitute for that
which requires changing; the sulphate of ammonia which has been
washed out is evaporated and treated in the usual way. There will
always be plenty of peroxide of iron peat after the first operation upon
the gas, resulting from the peat that has taken up the ammonia, for
when the ammonia has been washed out of it, and it has been exposed
to the atmosphere, it becomes a peroxide peat; when you first com-
mence, however, to purify gas, and have not a peroxide peat, you must
substitute a sulphate of iron peat which has been mixed with such a
proportion of hydrate of lime as will decompose the sulphate of iron,
forming a peroxide of iron and a sulphate of lime. The quantity of
lime required to do this will of course depend upon the proportion
of sulphate of iron contained in the peat; say, there is 28 per cent.
of sulphate of iron present, you will then require for every 100 lbs. of
such peat 12. of hydrate of lime. The presence of the sulphate of
lime in the peroxide peat is rather disadvantageous; that peat, therefore,

page_text: from which the ammonia has been washed out, should always be used.
after the first operation. The peroxide of iron peat may be used over
and over again to deprive gas of its sulphuretted hydrogen in the
manner I have already described; it may be used a dozen times or.
more until the sulphur deposited impairs the free flow of the gas;
from the peat so charged with sulphur may be readily obtained
by sublimation. Sulphate of lime peat, that is, peat more or less
saturated with sulphate of lime, is to be found in many localities;
it inay be economical, therefore, to use such peat at many gas works
to deprive gas of its ammonia; where it is used it is better to make
it the second vessel through which the gas passes: the reason of this
will be obvious to every chemist, for the various impurities con-
tained in the gas coming in contact with the sulphate of lime would
cause a variety of decompositions, which would render the process of
obtaining the commercial salts of ammonia very troublesome; all
this will be avoided by first passing the gas through the peroxide.
peat, so as to deprive it of its sulphuretted hydrogen; it then passes.
through the sulphate of lime, where the sulphuric acid contained in
the lime siezes upon the ammonia, forming sulphate of ammonia,
the lime at the same time taking up the carbonic acid.
,
I have stated that peat containing 40 per cent. of a peroxide or sul-
phate of iron may be considered the maximum for working bene-:
ficially, as the gas is apt to cause a. back pressure upon the retorts.
when the substance is more dense; where peat is found richer than
this it will be desirable to mix it with a lighter peat, or peat charcoal,
so as to bring it down to about 40 per cent.; and in other cases, where
the peat does not contain a sufficient quantity of the peroxide or sul-
phate of iron, the requisite per-centage may be obtained by mixing the..
richer or more dense with the poorer peats, or by burning some peat-
and mixing the ashes with other peat in sufficient quantity to obtain
the desired strength, or by causing the natural solution of iron as it
escapes out of the rock or soil to flow amongst a quantity of peat that:
has been previously dried, removing it when saturated, and drying it
again, repeating the operation from time to time until the desired
strength of iron is obtained. I mix chloride of sodium (common salt).
with peat or peat charcoal to charge the purifier for depriving gas of,

page_text: its, ammonia; the peat may be of the kinds I have described, con
taining iron or lime, or it may be the common rich vegetable. peat; the
quantity of salt had better not exceed 20 per cent., and it will mix:
much better with the peat if it is first made into a saturated solution
with water. There will be left in the peat muriate of ammonia, which
may be washed out and treated in the usual manner. I produce a
manure by combining certain substances with the residual matters left
by the gas after it has passed through the ammonia purifier. I make
use. of the following composition, the proportions, however, may be
varied Superphosphate. of lime, 24 parts, by weight; bisulphate of.
potassa, 16; chloride of sodium, 7; sulphate of magnesia; 8; peat, 45;
the whole to, be well mixed, and incorporated together by any me-
chanical means, and placed in the ammonia purifier, which I have.
above called vessel No. 1. I have described the peats combined with
iron, because I have in every instance found them the most efficient
for the purification of gas. I have found in peat bogs, however, peats
containing oxides or sulphates of manganese and copper; these .or. either:
of them may be used profitably for purifying gas, and treated in a
similar manner to that above described for iron peats. The ordinary:
ammoniacal liquor of gas works I treat in the following manner, so as:
to deprive it of its sulphuretted hydrogen, and convert the sulphide of
ammonium into a sulphate of ammonia: there should be three filters,
and we will call them A, B, and C.. A, and B, are placed side by side;
C, is placed higher, so that its front edge rests rests upon the back edges.
of A," and B, like steps of a staircase; all filters should be divided
crossways by partitions, three or four will be a convenient number;
they should be moveable for: the convenience of emptying, and about
2' feet apart will be found a desirable space; the first partition is flush
with the top of the-filter; but does not reach within two inches. of the
bottom; the second partition goes home at the bottom, but does not
reach the top by two inches; the third, again, is flush with the top,
but does not reach within two inches of the bottom, and so on alter-.
nately according to the number of partitions; from the last division
of C, there is an exit pipe, having two branches, with a stop cock
attached to each; one of these branches opens into the first division
of A, the other in a similar manner into B. C, is filled with a peroxide.

page_text: of iron peat, for that which has been removed from the purifier, and
from which the sulphate of ammonia has been washed out....A, and B,
are filled with a sulphate of lime or a sulphate of iron peat, a perforated
piece of wood or iron is placed upon the: peat in the first division of
each of the filters, so as to distribute the liquid, when pumped up/over
the surface of the peat beneath; in the last divisions of A, and B; there
are also exit pipes, from which the solution of sulphate of ammonia may
be received into any convenient vessel for the purpose of evaporating
down, so as to produce a commercial sulphate of ammonia. We shall
suppose the filters are charged and ready for operation, the stop cocks
being closed. We first open the stop cock of the branch pipe from C
and which enters the first division of A: We then pump: up 'the foul
ammoniacal liquor into the first division of C, 'the liquid being received
upon the perforated metal or wood; the fluid descends the 1st division;
ascends the second, again descends the third, and so on alternately until
it reaches the exit pipe; which conducts it into the first division of A
The same chemical action takes place upon the foul ammóniacal liquor
in its passage through filter C, as takes place upon the gas in its passage
through No. 2, purifying. vessel, that is, it decomposes, its sulphuretted
hydrogen; it also arrests tar and other impurities that have been held
in suspension. A clear liquid, will now flow into A; holding in solution
a carbonate of ammonia and caustic ammonia, and will pass through the
filter by descending and ascending, as described with C; in its passage
the sulphuric acid of the lime or of the iron will seize upon the am-
monia, and convert it into a sulphate; the pure solution of sulphate of
ammonia will pass away by the exit pipe at the last division; when
all the sulphuric acid contained in A, has been combined with am-
monia, A, should be shut off from C, by turning the stop cock; that
which communicates between B, and C, should be opened: it will at
once be ascertained when this is necessary by exposing a piece of
turmeric paper to the fluid at the exit pipe of A.; as soon as the tur-
meric changes to a brown color, stop at once; steam or water should
now be passed through A, to wash out all the sulphate of ammonia;
when the liquid from the exit pipe is mixed with a little caustic lime,
and does not smell of ammonia, it is sufficiently washed. The con-
tents may now be removed from A, and, for the convenience of the

page_text: workmen, the partitions may be withdrawn'; it is then charged with
fresh sulphate peat, to be ready when B, has ceased to take up am-
monia. If it is a a sulphate of iron peat that has been used, it may be
spread out exposed to the atmosphere, and used for charging C, filter,
or No. 2, gas purifying vessel; of course, the same process takes place
in filter B, that took place in A; filter C, will last a long time. To
know when it should be fresh charged, hold a piece of white paper,
moistened with a solution of acetate of lead, to the fluid as it flows
into A, or B; if the paper is stained black it is time to change.
Having now described the nature of my Invention, and the manner
in which the same is to be performed, I would here observe that I do
not confine myself to the precise details hercin set forth, or in the
proportions given, as they may be varied according to the nature;
quality, or weight, or other varying properties of the articles used, so as
to suit or give effect to the processes I have described, nor do I lay
any claim to any of the substances, fluids, or other matters or things
herein mentioned, taken seperately, and not in combination, for the
purposes of my Invention.
In witness whereof, I, the said William Chisholm, have herein-
before affixed my hand and seal, this Twenty-first day of
November, in the year of our Lord One thousand eight hun-
dred and fifty-three.
Witness,
W CHISHOLM. (L.S.)
JOHN GEDGE,
Patent Agent,
4, Wellington South, Strand, London.