For this reason, and for the practically identical one that it is
quite free from dirt or insoluble matter, diluted spirit is specially
suitable for the protection of the water in cyclists' acetylene lamps,
[Footnote: As will appear in Chapter XIII., there is usually no holder in
a vehicular acetylene lamp, all the water being employed eventually for
the purpose of decomposing the carbide. This does not affect the present
question. Dilute alcohol does not attack calcium carbide so energetically
as pure water, because it stands midway between pure water and pure
alcohol, which is inert. The attack, however, of the carbide is as
complete as that of pure water, and the slower speed thereof is a
manifest advantage in any holderless apparatus.] where strict economy is
less important than smooth working. For domestic and larger installations
it is not indicated. As between calcium chloride and glycerin there is
little to choose; the former will be somewhat cheaper, but the latter
will not be prohibitively expensive if the high-grade pure glycerins of
the pharmacist are avoided. The following tables show the amount of each
substance which must be dissolved in water to obtain a liquid of definite
solidifying point.
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