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15
during its passage from the works or during its combustion
be converted into the more objectionable sulphuretted hydrogen.
No sample of coal gas is absolutely free from the
presence of sulphur, in the form of bisulphide of carbon, the
quantity usually varying from about 10 to 30 or 40 grains
per 100 cubic feet of gas.
2nd.—The great insignificance of the presence of even the
higher amount when reasonably considered.
It is evident that the correct way of speaking of this
impurity, when the effects it produces are being considered,
is as of sulphurous acid gas—this product being the one into
which the whole of the sulphur present in the gas at once
goes on combustion, and the form in which the supposed evil
is done.
It appears likely to mislead to speak of an impurity as so
many grains per cubic feet. It should rather be grains in
grains or cubic inches in cubic feet, and as it is with volume
and not weight we have most to do, the latter is preferable.
One grain of sulphur contained in the coal gas as bisulphide
of carbou, when burnt, produces 2.8 cubic inches of
sulphurous acid gas; so that 3.3 cubic feet of coal gas
containing 30 grains of sulphur per 100 cubic feet would
have to be burnt in order to produce this amount, or an
ordinary fish-tail burner for the space of nearly an hour.
Further, the quantity of sulphurous acid gas produced is
related, not so much to the quantity of gas in which it
occurs, but to the capacity of the apartment in which the gas
is burnt.
Taking about the smallest habitable room in which a gas
jet would be burned, one say, 6ft. by Oft. by 8ft.; this would
give the infinitesimal amount of .00056 per cent. in volumes
of sulphurous acid gas spread over the space of one hour, a
quantity that need not be considered.
Again. Two fish-tail burners, burning gas for six hours
continuously, at the rate of 4 cubic feet each per hour, will
give off during that time 43'6 cubic inches of sulphurous
acid gas, a quantity equal to .0009 per cent. of the volume