IMPROVEMENTS IN THE MANUFACTURE OF GAS
Year: 1858

page_text: LETTERS PATENT to John Leslie, of Conduit Street, St. George's,
Hanover Square, in the County of Middlesex, for the Invention of
"IMPROVEMENTS IN THE MANUFACTURE OF GAS."
Sealed the 10th May 1859, and dated the 18th November 1858.
PROVISIONAL SPECIFICATION left by the said John Leslie at the
Office of the Commissioners of Patents, with his Petition, on the
18th November 1858.
I, JOHN LESLIE, of Conduit Street, St. George's, Hanover Square, in the
County of Middlesex, do hereby declare the nature of the Invention for
"IMPROVEMENTS IN THE MANUFACTURE OF Gas," to be as follows:-
This Invention has for its object improvements in the manufacture of gas.
Heretofore in manufacturing gas from coal and other bituminous mineral
substances it has been usual to subject them to the process of destructive
distillation, and then to purify the gas obtained. Now, my improvements in
the manufacture of gas for the purposes of illumination from parrot coal,
cannel coal, boghead coal, and other mineral bituminous matters capable of
affording paraffine, consists in subjecting such mineral bituminous matters to
distillation at low temperatures, as is well understood, in order to obtain the
products distilled over in a condensed liquid form, and then to subject such
liquids to processes of purification, in order to fix or remove the ammonia,
sulphur, and other impurities, and then to subject the purified liquids to
destructive distillation, by which very pure gas is obtained.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said John Leslie in the Great Seal Patent Office on the
17th May 1859.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JOHN
LESLIE, of Conduit Street, St. George's, Hanover Square, in the County of
Middlesex, 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 fifty-eight, in the twenty-second year of
Her reign, did, for Herself, Her heirs and successors, give and grant unto me,
the said John Leslie, Her special licence that I, the said John Leslie,
my executors, administrators, and assigns, or such others as I, the
said John Leslie, 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 night make,
use, exercise, and vend, within the United Kingdom of Great Britain and
Ireland, the Channel Islands, and Isle of Man, an Invention for "IMPROVE-
MENTS IN THE MANUFACTURE OF GAS," upon the condition (amongst others)
that I, the said John Leslie, my executors or administrators, by an instru-
ment in writing under my, or their, or one of their hands and seals,
should particularly describe and ascertain the nature of the said Inven-
tion, 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 Leslie, 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 thereof, that is to say:-
This Invention has for its object improvements in the manufacture of gas.
Heretofore in manufacturing gas from coal and other bituminous mineral
substances it has been usual to subject them to the process of destructive
distillation, and then to purify the gas obtained. Now, my improvements in
the manufacture of gas for the purposes of illumination from parrot coal,
cannel coal, boghead coal, and other mineral bituminous matters capable of
affording paraffine, consist in subjecting such mineral bituminous matters to
distillation at low temperatures, as is well understood, in order to obtain the
products distilled over in a condensed liquid form, and then to subject such
liquids to processes of purification, in order to fix or remove the ammonia,

page_text: sulphur, and other impurities, and then to subject the purified liquids to
destructive distillation, by which very pure gas is obtained.
Having thus stated the nature of my said Invention, I will proceed more
fully to describe the manner of performing the same.
In the manufacture of gas from coal by destructive distillation as at present
practised in gas works, it is necessary to employ very extensive and at the
same time very expensive machinery and processes between the retorts where
the gas is distilled off and the gasometers wherein the gas is stored for
distribution, and the necessity for the use of such machinery and processes
arises from the high temperatures employed in distilling over every vapour-
izable constituent of the coals employed, by which not only is the illu-
minating gas distilled off, but also very inferior and deteriorating gases, with
products of sulphur and other impure matters, which are prejudicial not
only in respect to the illuminating powers of the combined gases, but they aro
also injurious in other respects. And it is for the purposes of purifying the
gases from the sulphur and other impure products that gasworks have heretofore
found it necessary to employ such extensive and expensive machinery and
processes. In addition to the above objections, large quantities of tar, as well
as of very offensive products, result from the present system of manufacturing
gas from coal at gas works, resulting in a great waste in regard to the quantity
of good and pure illuminating gas a given weight of coal is capable of affording.
Now, according to my Invention illuminating gas may be manufactured from
coal and other bituminous mineral in such manner as to dispense with the
use of the machinery and processes now necessary in gas works for purifying
the gases after they leave the retorts, and before they arrive at the gasometers.
And my Invention consists in so arranging gas works as to employ in the
manufacture of gas the hydrocarbon products of coal or other bituminous
minerals obtained by distilling such substances at a low temperature, whereby
I am enabled to dispense with the machinery and processes used for purifying
illuminating gas obtained by the existing process of destructive distillation of
the bituminous mineral; for these purposes cannel coal, parrot coal, boghead
coal, and other coal, and other mineral bituminous matters, are distilled at a
low temperature, in such manner as to obtain the products in a condensed
form in place of in the state of gases; then, when necessary, the resulting.
fluids are purified, and then such fluids are subjected to the action of heat in
a finely divided state in retorts or vessels, to convert them into gas, which is
conveyed into gasometers such as heretofore used at gas works, in order that
the same may be distributed therefrom, as heretofore practised.
I would here state that separately it is not new to obtain condensed fluid

page_text: products by distilling coal and other mineral bituminous matters at low
temperatures, but such process has not been resorted to as a preparatory step
in the manufacture of illuminating gas at gasworks.
I would remark that, although various forms of retorts or vessels may be
employed for distilling coal and other bituminous mineral substances at a low
temperature, I prefer to use a cylindrical retort heated externally by a fire,
such retort being caused constantly to revolve slowly. Into this or other
suitable retort the coal or bituminous mineral is introduced, broken up into
small pieces, and the products evolved pass off to the condensing apparatus,
which is constantly kept cool by water, and the condensed hydrocarbon pro-
ducts are received into a suitable receiver or vessel. Care is to be taken to
keep down the heat of the retort, in order to prevent the production of gas or
vapours which will not condense, the object being to obtain only fluid hydro-
carbons by the first process of distillation.
When using the better classes of cannel coal the hydrocarbons obtained may
at once be employed for the manufacture of gas, as herein-after explained, but
when using hydrocarbons (obtained from less pure coal or other bituminous
mineral) which have nitrogenous and sulphur compounds combined therewith,
I purify the same in the following manner :-To remove the nitrogen I wash
the crude hydrocarbons with dilute acid; dilute sulphuric acid will answer
the purpose, but I prefer to use dilute muriatic acid, prepared by adding five
gallons of water to one gallon of the concentrated muriatic acid of commerce;
I then agitate the hydrocarbons violently with this diluted acid, using 15
gallons of the diluted acid to every ton of the oil. The mixed hydrocarbons
and acid is then allowed to stand for twelve hours, at a temperature of 90°
to 100° Fahrenheit, and then the layer of acid liquor which will have separated
must be drawn off. To free the hydrocarbons from sulphur compounds, I use
at the rate of 1 lb. caustic soda with one gallon of water, and from four-
teen to thirty gallons of such solution will be found sufficient to purify a ton of
the hydrocarbon fluid; for this purpose the solution is well stirred into the
bydrocarbons, and then allowed to settle for some hours, when the purified
hydrocarbons may be readily drawn off from the impurities.
When the coal or other mineral bituminous substance contains a large
quantity of sulphur, one of the two following processes may be resorted to with
advantage prior to distillation, to prevent any sulphurous constituent from
distilling over with the hydrocarbons; first, I mix the coal with 10 per cent.
of slaked lime before distillation, and then distil, as before described; or,
second, I steep the coal when broken in small pieces for from three to six
hours in a liquor made by dissolving in the proportion of 1 lb, of common salt

page_text: in one gallon of water, and adding lb. of quicklime thereto. After the coal
has been thus steeped it is to be removed from the liquor, and dried either by
exposure to the air or by the application of a gentle heat, and then distil as
before described.
In order to convert the hydrocarbon liquid into illuminating gas, it is
caused to drop into a retort or vessel heated to a good red heat, and the gas
is conveyed from the retort into gasometers of the ordinary construction, from
which the illuminating gas is supplied to the gas mains, as gas has heretofore
been supplied from gasometers.
By these improvements not only will gas works be rendered less objectionable
in any neighbourhood, but the gas obtained will be more pure, and the cost of
production will be greatly reduced.
In witness whereof, I, the said John Leslie, have hereunto set my hand
and seal, this Seventeenth day of May, in the year of our Lord One
thousand eight hundred and fifty-nine.
י זג
LESL
TATTAT третте
TTT
JOHN PEDRER
JOHN
(L.D.)