Moreover, a
hand-fed carbide-to-water generator will work satisfactorily with only
half a gallon [Footnote: The United States National Board of Fire
Underwriters stipulates for the presence of 1 (American) gallon of water
for every 1 lb. of carbide before such an apparatus is "permitted." This
quantity of liquid might retain nearly 4 per cent. of the total acetylene
evolved. Even this is an exaggeration; for neither her, nor in the
corresponding figure given in the text, is any allowance made for the
diminution in solvent power of the water as it becomes heated by the
reaction.] of liquid present for every 1 lb. of carbide decomposed, and
were all this water run off and a fresh quantity admitted before each
fresh introduction of carbide, the loss of acetylene by dissolution could
not exceed 2 per cent. of the total make, assuming the carbide to be
capable of yielding 5 cubic feet of gas per lb. Admitting, however, that
some loss of gas does occur in this manner, the defect is partly, if not
wholly, neutralised by the concomitant advantages of the system: (1)
granted that the generator is efficiently constructed, decomposition of
the carbide is absolutely complete, so that no loss of gas occurs in this
fashion; (2) the gas is evolved at a low temperature, so that it is
unaccompanied, by products of polymerisation, which may block the leading
pipes and must reduce the illuminating power; (3) the acetylene is not
mixed with air (as always happens at the first charging of a water-to-
carbide apparatus), which also lowers the illuminating power; and (4) the
gas is freed from two of its three chief impurities, viz.
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