Thus at 10 atmospheres
the presence of the acetone is a source of safety; but at 20 atmospheres
it becomes an extra danger.
Since sound steel cylinders may easily be constructed to boar a pressure
of 250 atmospheres, but would be burst by a pressure considerably less
than 5000 atmospheres, it appears that liquefied acetylene and its
solution in acetone at a pressure of 20 atmospheres are quite unsafe; and
it might also seem that both the solution at a pressure of 10 atmospheres
and the simple gas compressed to the same limit should be safe. But there
is an important difference here, in degree if not in kind, because, given
a cylinder of known capacity containing (1) gaseous acetylene compressed
to 10 atmospheres, or (2) containing the solution at the same pressure,
if an explosion were to occur, in case (1) the whole contents would
participate in the decomposition, whereas in case (2), as mentioned
already, only the small quantity of gaseous acetylene above the solution
would be dissociated.
It is manifest that of the three varieties of compressed acetylene now
under consideration, the solution in acetone is the only one fit for
general employment; but it exhibits the grave defects (_a_) that the
pressure under which it is prepared must be so small that the pressure in
the cylinders can never approach 20 atmospheres in the hottest weather or
in the hottest situation to which they may be exposed, (_b_) that
the gas does not escape smoothly enough to be convenient from large
vessels unless those vessels are agitated, and (_c_) that the
cylinders must always be used in a certain position with the valve at the
top, lest part of the liquid should run out into the pipes.
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