Acetylene, the Principles of Its Generation and Use | Page 3

from a raw material--calcium carbide--which, relatively to the yield of
light of the gaseous product, is less bulky than the raw materials of
other gases. In comparison also with oils and candles, calcium carbide
is capable of yielding, through the acetylene obtainable from it, more
light per unit of space occupied by it. This higher light-yielding
capacity of calcium carbide, ready to be developed through acetylene,
gives the latter gas a great advantage over all other illuminants in
respect of compactness for transport or storage. Hence, where facilities
for transport or storage are bad or costly, acetylene may be the most
convenient or cheapest illuminant, notwithstanding its relatively high
cost in many other cases. For example, in a district to which coal and
oil must be brought great distances, the freight on them may be so
heavy that--regarding the question as simply one of obtaining light in
the cheapest manner--it may be more economical to bring calcium
carbide an equal or even greater distance and generate acetylene from it
on the spot, than to use oil or make coal-gas for lighting purposes,
notwithstanding that acetylene may not be able to compete on equal
terms with oil--or coal-gas at the place from which the carbide is
brought. Likewise where storage accommodation is limited, as in
vehicles or in ships or lighthouses, calcium carbide may be preferable
to oil or other illuminants as a source of light. Disregarding for the
moment intrinsic advantages which the light obtainable from acetylene
has over other lights, there are many cases where, owing to saving in
cost of carriage, acetylene is the most economical illuminant; and many
other cases where, owing to limited space for storage, acetylene far
surpasses other illuminants in convenience, and is practically
indispensable.
The light of the acetylene flame has, however, some intrinsic
advantages over the light of other artificial illuminants. In the first
place, the light more closely resembles sunlight in composition or
"colour." It is more nearly a pure "white" light than is any other flame
or incandescent body in general use for illuminating purposes. The
nature or composition of the light of the acetylene flame will be dealt

with more exhaustively later, and compared with that afforded by other
illuminants; but, speaking generally, it may be said that the
self-luminous acetylene light is superior in tint, to all other artificial
lights, for which reason it is invaluable for colour-judging and
shade-matching. In the second place, when the gas issues from a
suitable self-luminous burner under proper pressure, the acetylene
flame is perfectly steady; and in this respect it in preferable to most
types of electric light, to all self- luminous coal-gas flames and candles,
and to many varieties of oil-lamp. In steadiness and freedom from
flicker it is fully equal to incandescent coal-gas light, but it in distinctly
superior to the latter by virtue of its complete freedom from noise. The
incandescent acetylene flame emits a slight roaring, but usually not
more than that coming from an atmospheric coal-gas burner. With the
exception of the electric arc, self-luminous acetylene yields a flame of
unsurpassed intensity, and yet its light is agreeably soft. In the third
place, where electricity is absent, a brilliancy of illumination which can
readily be obtained from self-luminous acetylene can otherwise only be
procured by the employment of the incandescent system applied either
to coal-gas or to oil; and there are numerous situations, such as
factories, workshops, and the like, where the vibration of the machinery
or the prevalence of dust renders the use of mantles troublesome if not
impossible. Anticipating what will be said later, in cases like these, the
cost of lighting by self-luminous acetylene may fairly be compared
with self-luminous coal- gas or oil only; although in other positions the
economy of the Welsbach mantle must be borne in mind.
Acetylene lighting presents also certain important hygienic advantages
over other forms of flame lighting, in that it exhausts, vitiates, and
heats the air of a room to a less degree, for a given yield of light, than
do either coal-gas, oils, or candles. This point in favour of acetylene is
referred to here only in general terms; the evidence on which the
foregoing statement is based will be recorded in a tabular comparison
of the cost and qualities of different illuminants. Exhaustion of the air
means, in this connexion, depletion of the oxygen normally present in it.
One volume of acetylene requires 2-1/2 volumes of oxygen for its
complete combustion, and since 21 volumes of oxygen are associated
in atmospheric air with 79 volumes of inert gases--chiefly

nitrogen--which do not actively participate in combustion, it follows
that about 11.90 volumes of air are wholly exhausted, or deprived of
oxygen, in the course of the combustion of one volume of acetylene. If
the light which may