Acetylene, the Principles of Its Generation and Use | Page 5

of acetylene and paraffin for the illumination of country residences, it
may be remarked that an extraordinarily great amount of care must he
bestowed upon each separate lamp if the whole house is to be kept free
from an odour which is very offensive to the nostrils; and the time
occupied in this process, which of itself is a disagreeable one, reaches
several hours every day. Habit has taught the country dweller to accept
as inevitable this waste of time, and largely to ignore the odour of
petroleum in his abode; but the use of acetylene entirely does away
with the daily cleaning of lamps, and, if the pipe-fitting work has been
done properly, yields light absolutely unaccompanied by smell. Again,
unless most carefully managed, the lamp-room of a large house, with
its store of combustible oil, and its collection of greasy rags, must
unavoidably prove a sensible addition to the risk of fire. The analogue
of the lamp- room when acetylene is employed is the generator-house,
and this is a separate building at some distance from the residence
proper. There need be no appreciable odour in the generator-house,
except during the times of charging the apparatus; but if there is, it
passes into the open air instead of percolating into the occupied
apartments.
The amount of heat developed by the combustion of acetylene also is
less for a given yield of light than that developed by most other
illuminants. The gas, indeed, is a powerful heating gas, but owing to
the amount consumed being so small in proportion to the light
developed, the heat arising from acetylene lighting in a room is less
than that from most other illuminating agents, if the latter are employed
to the extent required to afford equally good illumination. The ratio of
the heat developed in acetylene lighting to that developed in, _e.g._,
lighting by ordinary coal-gas, varies considerably according to the
degree of efficiency of the burners, or, in other words, of the methods

by which light is obtained from the gases. Volume for volume,
acetylene yields on combustion about three and a half times as much
heat as coal- gas, yet, owing to its superior efficiency as an illuminant,
any required light may be obtained through it with no greater evolution
of heat than the best practicable (incandescent) burners for coal-gas
produce. The heat evolved by acetylene burners adequate to yield a
certain light is very much less than that evolved by ordinary flat-flame
coal-gas burners or by oil-lamps giving the same light, and is not more
than about three times as much as that from ordinary electric lamps
used in numbers sufficient to give the same light. More exact figures
for the ratio between the heat developed in acetylene lighting and that
in other modes of lighting are given in the table already referred to.
In connexion with the smaller amount of heat developed per unit of
light when acetylene is the illuminant, the frequently exaggerated claim
that acetylene does not blacken ceilings at all may be studied. Except it
be a carelessly manipulated petroleum-lamp, no form of artificial
illuminant employed nowadays ever emits black smoke, soot, or carbon,
in spite of the fact that all luminous flames commercially capable of
utilisation do contain free carbon in the elemental state. The black mark
on a ceiling over a source of light is caused by a rising current of hot air
and combustion products set up by the heat accompanying the light,
which current of hot gas carries with it the dust and dirt always present
in the atmosphere of an inhabited room. As this current of air and burnt
gas travels in a fairly concentrated vertical stream, and as the ceiling is
comparatively cool and exhibits a rough surface, that dust and dirt are
deposited on the ceiling above the flame, but the stain is seldom or
never composed of soot from the illuminant itself. Proof of this
statement may be found in the circumstance that a black mark is
eventually produced over an electric glow-lamp and above a pipe
delivering hot water. Clearly, therefore, the depth and extent of the
mark will depend on the volume and temperature of the hot gaseous
current; and since per unit of light acetylene emits a far smaller
quantity of combustion products and a far smaller amount of heat than
any other flame illuminant except incandescent coal-gas, the inevitable
black mark over its flame takes very much longer to appear. Quite
roughly speaking, as may be deduced from what has already been said
on this subject, the luminous flame of acetylene "blackens" a ceiling at

about the same rate as a coal-gas burner of the best Welsbach type.
There is one respect in which acetylene and other flame illuminants are
superior to electric lighting, viz., that