ON THE GASES EVOLVED FROM IRON FURNACES. 153 
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question in a way certainly somewhat tedious, but not the less positive. In the 
first place, it was necessary to be satisfied of the correctness of the opinion 
generally received, but, as far as we are aware, unproved, that the gaseous 
products of distillation of coal, in addition to carbonic oxide, hydrogen, ole- 
fiant gas and carburetted hydrogen, still contained other hydrocarbons. If 
the latter be absent, we are able by a eudiometric analysis to determine the 
constituents of a mixture of gases containing four ingredients, if we estimate 
for a given volume of the mixture A, the quantity of oxygen necessary for its 
combustion B, and the carbonic acid thus formed C, and also the proportion 
of the latter to the amount of aqueous vapour produced. Thus it requires 
A mixture consisting of 1 vol. H+1 vol. H.C +1 vol. HC +1 vol.CO =4 vol. 
for combustion ......... 1vol.0+2 vol. O+3 vol.O +4 vol. O =6 vol. 
from which is produced 1 vol. CO,+2 vol. CO.+1 vol. CO, =4 vol. 
and also ......seeee+-ee-e- 1 Vol. HO+2 vol. HO+2 vol. HO =5 vol. 
If we denote these quantities by the same letters as above, the olefiant 
gas by z, and the proportion of the aqueous vapour produced by the com- 
bustion to the carbonic acid as Ee the following four equations result : 
a+y+z+p =A, 
ut 2y+3z2+ap=B, 
yt+t22+p =v, 
x+2y+ 22 ma 8 
y+22+p E 
The value of the four unknown quantities x, y, 2 and p, are thus deter- 
mined :— 
- 
Sy Rae RY 
e=2A+4B 30 (p+5); 
on 
y=—2A—6B+5C(2 +1). 
2 
s=A4+4B—8C(- +1). 
Ws p=-2B+C(7+2). 
If the mixture of gases contain actually only the four assumed consti- 
tuents, we obtain positive values for x, y, 2 and p. If one of these quan- 
tities be negative, this is a proof that the mixture must contain other com- 
pounds than those assumed. 
In order to obtain something conclusive as to the nature of coal-gas, a 
quantity of coal was heated to redness in a combustion-tube, in such a man- 
ner that the gaseous products of distillation were not obliged to traverse the 
red-hot layers of coal. The gas was first conducted into a cool receiver, 
where it deposited the liquid products of distillation, after which it was freed 
from carbonic acid and sulphuretted hydrogen by means of a solution of 
oxide of lead in potash, and also from water by being made to pass through 
a tube filled with chloride of calcium, leading into a.eudiometer standing 
over mercury. An indefinite quantity of the gas was also led over red-hot 
oxide of copper, and yielded 0°23749 grm. carbonic acid and 0°2239 grm. 
water, which correspond with 120°55 cubic centimetres of carbonic acid, and 
