284 PRESENT STATE OF THE CHEMISTRY OF GAS-LIGHTING. 
sewage, and the mud of a stagnant pool. It also forms from 79 to 91 per cent, of the 
fire-damp of coal mines, and it constitutes from 30 to 60 per cent, of coal gas. It is 
colourless, odourless, tasteless, and without action on the animal body, for miners breathe 
it with impunity. It is a little more than half the weight of atmospheric air, its speci¬ 
fic gravity being 0-5531; and therefore 100 cubic inches of the gas weigh 17-15. grains. 
It burns, as you perceive, with a pale yellow flame, which is bluish for a considerable 
distance up, the height of the jet being somewhat less than that of coal gas, and so also 
is its illuminating power. A cubic foot of gas consumes 2 cubic feet of oxygen, or 10 
cubic feet of air; and the products of the combustion are a cubic foot of carbonic acid, 
and aqueous vapour. The heat of the flame is about 5890° Fahr., and a cubic foot will 
raise 16,920 ounces of water, or 52,000 cubic feet of air, 1° Fahr. The gas is but slightly 
absorbed by water, 100 volumes taking up 3‘91 of the gas. It is not absorbed by chlo¬ 
rine, except after some time, and in the light; nor by bromine or fuming sulphuric 
acid; and it is not easily decomposed by heat, nor is it condensed by cold. There is no 
immediate test for the gas. 
Besides marsh gas, there are probably other members of the series present in coal gas, 
as Ethyl-hydride (C 4 FI 6 ), Propyl-hydride (C c H s ), Butyl-hydride (C 8 H 10 ), and Amyl- 
hydride (C 10 H 12 ), all of which are found in the petroleums of commerce. 
(b) Olefiant Gas, Ethylene, or Elayl (C 4 H 4 ), is a gas which contains twice as 
much carbon in a given volume as the last—a volume of it contains its own bulk of car¬ 
bon vapour and two volumes of hydrogen. It exists in fire-damp to the extent of from 
2 to 16 per cent., and in coal gas too from 8 to 27 per cent., cannel gas containing it in 
the largest proportion. It is colourless, and, when pure, is a little ethereal or sweetish 
in its odour, and is anaesthetic or stupefying in its action on the body when it is inhaled. 
It is very nearly as heavy as atmospheric air—its gravity being 0-967; and therefore 100 
cubic inches of it weigh nearly 30 grains. It burns with a long, bright yellow flame, 
the illuminating power of which is fully twice as great as the last. A cubic foot of the 
gas requires 3 cubic feet of oxygen or 15 cubic feet of air for its combustion, and it 
produces 2 cubic feet of carbonic acid, and much aqueous vapour, evolving about one- 
third more heat than the last. When mixed with twice its volume of chlorine gas and 
fired, its hydrogen is consumed, and its carbon is deposited in the form of soot. It is 
also slowly absorbed by chlorine, in the dark as well as in the light, forming a heavy 
oily liquid of an ethereal odour, called Dutch liquid (C 4 H 4 C1 o). In like manner it is 
absorbed by bromine, and by fuming sulphuric acid, The gas is slightly soluble in 
water, to the extent of about one-eighth of its volume, and it is freely soluble in alcohol, 
ether, volatile oil, and fixed oil. Turpentine, for example, will take up twice and a half 
times its volume of the gas, and olive oil will absorb its own volume of it. It is easily 
decomposed by heat—a red-heat converting it into carbon and marsh gas, together with 
a small quantity of tarry matter; and the gas is condensable by great cold and by pres¬ 
sure. The test for the gas is bromine or fuming sulphuric acid, which freely absorb it. 
(c) Propylene, or, as it is sometimes termed, Tritylene (C 6 H 6 ), is a compound of 
carbon and hydrogen in the same percentage proportions by weight as the last; but a 
volume of it contains volume of carbon vapour and 3 volumes of hydrogen. Its pro¬ 
portion in coal gas has not been accurately determined. It is colourless, and has a stu¬ 
pefying action on the body. It is just half as heavy again as atmospheric air, its spe¬ 
cific gravity being 1-455 ; and therefore 100 cubic inches of it weigh about 45 grains. 
It burns with a bright yellow and somewhat sooty flame, which is fully three times as 
long as the comparison jet of coal gas burning from the same-sized orifice and under 
the same pressure ; and^the light evolved from it is about three times as great as that 
from common coal-gas. A cubic foot of it requires 4-^ cubic feet of oxygen, or 22| 
cubic feet of air, to burn it; and it produces 3 cubic feet of carbonic acid, and much 
aqueous vapour. The heat evolved by it is also very great. It is but slightly absorbed 
by water, but it is freely absorbed by chlorine, bromine, and iodine, forming compounds 
which correspond to Dutch liquid. It is also absorbed by fuming sulphuric acid, and 
even by strong oil of vitriol. The volatile and fixed oils dissolve it, and so also does a 
solution of protochloride of copper. As in the last case, it is readily decomposed by a 
red-heat, forming marsh gas, and depositing carbon; and it is also condensed by cold and 
pressure. 
(d) Butylene, Tetrylene, Ditetryl, or Oil Gas (C S H 8 ), is a still further condensa¬ 
tion of carbon and hydrogen in the same percentage weights as in olefiant gas. A 
