Reference also to the abstracts of the official regulations as to
acetylene installations in foreign countries given in Chapter IV. will
show that they contain brief rules as to purifiers.
DRYING.--It has been stated in Chapter III. that the proper position for
the chemical purifiers of an acetylene plant is after the holder; and
they therefore form the last items in the installation unless a "station"
governor and meter are fitted. It is therefore possible to use them also
to remove the moisture in the gas, if a material hygroscopic in nature is
employed to charge them. This should be true more particularly with
puratylene, which contains a notable proportion of the very hygroscopic
body calcium chloride. If a separate drier is desirable, there are two
methods of charging it. It may be filled either with some hygroscopic
substance such as porous calcium chloride or quicklime in very coarse
powder, which retains the water by combining with it; or the gas may be
led through a vessel loaded with calcium carbide, which will manifestly
hold all the moisture, replacing it by an equivalent quantity of
(unpurified) acetylene. The objection is sometimes urged against this
latter method, that it restores to the gas the nauseous odour and the
otherwise harmful impurities it had more or less completely lost in the
purifiers; but as regards the first point, a nauseous odour is not, as
has previously been shown, objectionable in itself, and as regards the
second, the amount of impurities added by a carbide drier, being strictly
limited by the proportion of moisture in the damp gas, is too small to be
noticeable at the burners or elsewhere.
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