_Outline of the new art of procuring light by means of coal gas, and
Theory of the production of Gas Lights._
All substances, whether animal, vegetable, or mineral, consisting of
carbon, hydrogen, and oxigen, when exposed to a red heat, produce
various inflammable elastic fluids, capable of furnishing artificial
light.
The gases thus obtained are called carburetted hydrogen; they produce,
from their combustion, water and carbonic acid. The species of
carburetted hydrogen, procured from pit-coal, has of late been called
_coal gas_.
We perceive the evolution of this elastic fluid, during the combustion
of coal, in a common fire. The coal, when heated to a certain degree,
swells and kindles, and frequently emits remarkably bright streams of
flame. And after a certain period these appearances cease, and the coal
glows with a red light.
The flame produced from coal, wood, turf, oil, wax, tallow, or other
bodies, which are composed of carbon, hydrogen and oxigen, proceeds from
the production of carburetted hydrogen gas, evolved from the combustible
body when in an ignited state.
It must have been noticed at the same time, that in the common mode of
burning coal in a fire-place, or stove, nearly the whole of this
inflammable gaseous matter is lost. We often see a flame suddenly burst
from the densest smoke, and as suddenly disappear; and if a light be
applied to the little jets that issue from the bituminous part of the
coal, they will catch fire and burn with a bright flame. The fact is,
that the greater part of the carburetted hydrogen gas, capable of
affording light and heat, continually escapes up the chimney, during the
decomposition of the coal, whilst only a small part is occasionally
ignited, and exhibits the phenomena of the flame.
If coal instead of being burnt in the way now stated, is submitted at a
temperature of ignition in close vessels, all its immediate constituent
parts may be collected. The bituminous part is melted out in the form of
coal tar, there is disengaged at the same time a large quantity of an
aqueous fluid, contaminated with a portion of oil, and various
ammoniacal salts. A large quantity of carburetted hydrogen, carbonic
oxide, carbonic acid, and sulphuretted hydrogen also makes their
appearance, and the fixed base of the coal, alone remains behind in the
distillatory apparatus, in the form of a carbonaceous substance called
_coke_. An analysis of the coal is thus effected by the process of
destructive distillation. The products which the coal furnishes may be
separately collected in different vessels. The carburetted hydrogen, or
coal gas, when freed from the foreign gases may be propelled in streams
out of small apertures, which when lighted may serve as a flame of a
candle and then form what we now call GAS LIGHTS.
It is in this manner that from pitcoal a production of our own soil, we
procure a pure, lasting and brilliant light, which in other cases must
be derived from materials in part imported from abroad.
In order to apply this mode of procuring light on a large scale as now
practised with unparalleled success in this country, the coal is put
into vessels called retorts and furnished with pipes connected with
reservoirs to receive the distillatory products. The retorts are fixed
into a furnace, and heated to redness. The heat developes from the coal
the gaseous and liquid products, the latter are deposited into
receivers, and the former are conducted through water in which quick
lime is diffused by which the carburetted hydrogen gas is purified. The
sulphuretted hydrogen and carbonic acid which were mixed with it, become
absorbed by the quick-lime, and the pure carburetted hydrogen is stored
up in a vessel called the gas-holder, and is then ready for use.
From the reservoir in which the gas has been collected, proceed pipes,
which branch out into smaller ramifications until they terminate at the
place where the lights are wanted and the extremities of the branch
pipes are furnished with stop-cocks to regulate the flow of the gas into
the burners or lamps.
The production of gas-lights, is therefore analogous to that of flame
produced from tallow, wax, or oil. All these substances possess, in
common with coal, the elements of certain peculiar matters, which are
capable of being converted into inflammable elastic fluids by the
application of heat.
The capillary tubes, formed by the wick of a candle, or lamp, serve the
office of the retorts, placed in the heated furnace in the gas-light
process and in which the inflammable gaseous fluid is developed. The wax
tallow or oil, is drawn up into these ignited tubes, and is decomposed
into carburetted hydrogen gas, and from the combustion of this substance
the illumination proceeds. In the lamp as well as in the candle, the
oil, or tallow, must therefore be decomposed before they can produce a
light, but for this purpose the decomposition of a minute quantity of
the materials successively, is sufficient to give a good light. Thus
originates the flame of a candle or lamp.
Nothing more therefore is aimed at in the gas-light process, than to
separate the immediate products which coal affords, when submitted to a
temperature of ignition in a close vessel; to collect these products in
separate reservoirs, and to convey one of the products, the inflammable
gas, by means of pipes and branching tubes, to any required distance, in
order to exhibit it there at the orifice of the conducting tube, so that
it may be used as a candle or lamp.
The whole difference between the gigantic process of the gas light
operation, and the miniature operation of a candle or lamp, consists in
having the distillatory apparatus at the gas-light manufactory, instead
of being in the wick of a candle or lamp. In having the crude
inflammable matter decomposed previous to the elastic fluid being
wanted, and stored up for use, instead of being prepared and consumed as
fast as it proceeds from the decomposed oil, wax or tallow; and lastly,
in transmitting the gas to any required distance, and igniting it at
the burner or lamp of the conducting tube, instead of burning it at the
apex of the wick. The principle of the gas-light manufacture is
therefore rational, and justifiable by the general mode in which all
light is produced.
It only remains to be observed that while the new and important use to
which pitcoal may thus be applied, affords a strong confirmation of what
has been well observed, that of all subterraneous combustible
substances, coal is in this country by far the most important natural
production.[2] “It is connected not only with the necessities, comforts
and enjoyments of life, but also with the extension of our most
important arts, our manufactures, commerce and national riches.
[2] Davy on the Safety Lamp.
“Essential in affording warmth and preparing food, it yields a sort of
artificial sunshine and in some measure compensates for the
disadvantages of our climate.
“By means of it metallurgical processes are carried on, and the most
important materials of civilized life furnished, the agriculturist is
supplied with a useful manure and the architect with a necessary
cement. Not only manufactories and private houses, but even whole
streets and towns are lighted by its application, and in furnishing the
elements of activity in the steam-engine, it has given a wonderful
impulse to mechanical and chemical ingenuity, diminished to a great
extent human labour, and increased in a high degree the strength and
wealth of the country.”