The matter is
perhaps rendered more intelligible by employing the old name for calcium
hydroxide or slaked lime, viz., hydrated oxide of calcium, and by writing
its formula in the corresponding form, when equation (2) becomes
CaC_2 + 2H_2O = C_2H_2 + CaO.H_2O.
It is, therefore, absolutely correct to state that if the amount of
calcium carbide present in an acetylene generator is more than chemically
sufficient to decompose all the water introduced, no more, and
theoretically speaking no less, acetylene can ever be liberated than 26
parts by weight of gas for every 18 parts by weight of water attacked.
This, it must be distinctly understood, is the condition of affairs
obtaining in the ideal acetylene generator only; since, for reasons which
will be immediately explained, when the output of gas is measured in
terms of the water decomposed, in no commercial apparatus, and indeed in
no generator which can be imagined fit for actual employment, does that
output of gas ever approach the quantitative amount; but the volume of
water used, if not actually disappearing, is always vastly in excess of
the requirements of equation (2). On the contrary, when the make of gas
is measured in terms of the calcium carbide consumed, the said make may,
and frequently does, reach 80, 90, or even 99 per cent.
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