To determine the normal
reaction (No. 2) of an acetylene generator, 64 parts by weight of calcium
carbide must react with 36 parts of water to yield 26 parts by weight of
acetylene, and apparently both carbide and water are entirely consumed;
but if opportunity is given for the occurrence of reaction (3), another
64 parts by weight of carbide may be attacked, without the addition of
any more water, producing, inevitably, another 26 parts of acetylene. If,
then, water is in chemical excess in the generator, all the calcium
carbide present will be decomposed according to equation (2), and the
action will take place without delay; after a few minutes' interval the
whole of the acetylene capable of liberation will have been evolved, and
nothing further can possibly happen until another charge of carbide is
inserted in the apparatus. If, on the other hand, calcium carbide is in
chemical excess in the generator, all the water run in will be consumed
according to equation (2), and this action will again take place without
delay; but unless the temperature of the residual carbide has been kept
well below 400 deg. C., a further evolution of gas will occur which will not
cease for an indeterminate period of time, and which, by strict theory,
given the necessary conditions, might continue until a second volume of
acetylene equal to that liberated at first had been set free.
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