For
all such purposes wooden implements only are best employed; but the
remark does not apply to the hand-charging of a carbide-to-water
generator through its proper shoot. Before passing to another subject, it
may be remarked that a quantity of air far less than that which causes
acetylene to become dangerous is objectionable, as its presence is apt to
reduce the illuminating power of the gas unduly.
EFFECT OF HEAT ON CARBIDE.--Chemically speaking, no amount of heat
possible of attainment in the worst acetylene generator can affect
calcium carbide in the slightest degree, because that substance may be
raised to almost any temperature short of those distinguishing the
electric furnace, without suffering any change or deterioration. In the
absence of water, calcium carbide is as inert a substance as can well be
imagined: it cannot be made to catch fire, for it is absolutely
incombustible, and it can be heated in any ordinary flame for reasonable
periods of time, or thrown into any non-electrical furnace without
suffering in the least. But in presence of water, or of any liquid
containing water, matters are different. If the temperature of an
acetylene generator rises to such an extent that part of the gas is
polymerised into tar, that tar naturally tends to coat the residual
carbide lumps, and, being greasy in character, more or less completely
protects the interior from further attack.
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