Acetylene, the Principles of Its Generation and Use | Page 4

be developed by the acetylene is brought into
consideration, it will be found that, relatively to other illuminants,
acetylene causes less exhaustion of the air than any other illuminating
agent except electricity. For instance, coal-gas exhausts only about 6-
1/2 times its volume of air when it is burnt; but since, volume for
volume, acetylene ordinarily yields from three to fifteen times as much
light as coal-gas, it follows that the same illuminative value is
obtainable from acetylene by considerably less exhaustion of the air
than from coal-gas. The exact ratio depends on the degree of efficiency
of the burners, or of the methods by which light is obtained from the
gases, as will be realised by reference to the table which follows.
Broadly speaking, however, no illuminant which evolves light by
combustion (oxidation), and which therefore requires a supply of
oxygen or air for its maintenance, affords light with so little exhaustion
of the air as acetylene. Hence in confined, ill-ventilated, or crowded
rooms, the air will suffer less exhaustion, and accordingly be better for
breathing, if acetylene is chosen rather than any other illuminant,
except electricity.
Next, in regard to vitiation of the air, by which is meant the alteration
in its composition resulting from the admixture of products of
combustion with it. Electric lighting is as superior to other modes of
lighting in respect of direct vitiation as of exhaustion of the air, because
it does not depend on combustion. Putting it aside, however, light is
obtainable by means of acetylene with less attendant vitiation of the air
than by means of any other gas or of oil or candles. The principal
vitiating factor in all cases is the carbonic acid produced by the
combustion. Now one volume of acetylene on combustion yields two
volumes of carbonic acid, whereas one volume of coal-gas yields about
0.6 volume of carbonic acid. But even assuming that the incandescent
system of lighting is applied in the case of coal-gas and not of
acetylene, the ratio of the consumption of the two gases for the
development of a given illuminative effect will be such that no more
carbonic acid will be produced by the acetylene; and if the incandescent

system is applied either in both cases or in neither, the ratio will be
greatly in favour of acetylene. The other factors which determine the
vitiation of the air of a room in which the gas is burning are likewise
under ordinary conditions more in favour of acetylene. They are not,
however, constant, since the so-called "impurities," which on
combustion cause vitiation of the air, vary greatly in amount according
to the extent to which the gases have been purified. London coal-gas,
which was formerly purified to the highest degree practically attainable,
used to contain on the average only 10 to 12 grains of sulphur per 100
cubic feet, and virtually no other impurity. But now coal-gas, in
London and most provincial towns, contains 40 to 50 grains of sulphur
per 100 cubic foot. At least 5 grains of ammonia per 100 cubic foot in
also present in coal-gas in some towns. Crude acetylene also contains
sulphur and ammonia, that coming from good quality calcium carbide
at the present day including about 31 grains of the former and 25 grains
of the latter per 100 cubic feet. But crude acetylene is also accompanied
by a third impurity, viz., phosphoretted hydrogen or phosphine, which
in unknown in coal-gas, and which is considerably more objectionable
than either ammonia or sulphur. The formation, behaviour, and removal
of those various impurities will be discussed in


Chapter V.
; but here it may be said that there is no reason why, if calcium carbide
of a fair degree of purity has been used, and if the gas has been
generated from it in a properly designed and smoothly working
apparatus-- this being quite as important as, or even more important
than, the purity of the original carbide--the gas should not be freed from
phosphorus, sulphur, and ammonia to the utmost necessary or desirable
extent, by processes which are neither complicated nor expensive. And
if this is done, as it always should be whenever the acetylene is
required for domestic lighting, the vitiation of the air of a room due to
the "impurities" in the gas will become much less in the case of

acetylene than in that of even well-purified coal-gas; taking equal
illuminating effect as the basis for comparison.
Acetylene is similarly superior, speaking generally, to petroleum in
respect of impurities, though the sulphur present in petroleum oils, such
as are sold in this country for household use, though very variable, is
often quite small in amount, and seldom is responsible for serious
vitiation of the atmosphere.
Regarding somewhat more closely the relative convenience and safety