5 kilos., next to a pressure of 3.5 x 3.5 = 12 kilos,
per square centimetre, and finally drives it into the storage vessels.
Compression is effected in two stages, because the process is accompanied
by an evolution of much heat, which might cause the gas to explode during
the operation; but since the pump is fitted with two cylinders, the
acetylene can be cooled after the first compression. The storage vessels
then contain 100 times their apparent volume of acetylene; for as the
solubility of acetylene in acetone at ordinary temperature and pressure
is about 25 volumes of gas in 1 of liquid, a vessel holding 100 volumes
when empty takes up 25 x 43 = 1000 volumes of acetylene roughly at
atmospheric pressure; which, as the pressure is approximately 10
atmospheres, becomes 1000 x 10 = 10,000 volumes per 100 normal capacity,
or 100 times the capacity of the vessel in terms of water. From these
large vessels, portable cylinders of various useful dimensions, similarly
loaded with porous matter and acetone, are charged simply by placing them
in mutual contact, thus allowing the pressure and the surplus gas to
enter the small one; a process which has the advantage of renewing the
small quantity of acetone vaporised from the consumers' cylinders as the
acetylene is burnt (for acetone is somewhat volatile, cf.
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