C. as
long as any liquid water remains unevaporated, if an excess of water is
employed in an acetylene generator, the temperature inside can never--
except quite locally--exceed 100 deg. C., however fast the carbide be
decomposed. An indefinitely large consumption of water by evaporation in
a generator matters nothing, for the liquid may be considered of no
pecuniary value, and it can all be recovered by condensation in a
subsequent portion of the plant.
It has been said that the quantity of heat liberated when a certain
amount of carbide suffers decomposition is fixed; it remains now to
consider what that quantity is. Quantities of heat are always measured in
terms of the amount needed to raise a certain weight of water a certain
number of degrees on the thermometric scale. There are several units in
use, but the one which will be employed throughout this book is the
"Large Calorie"; a large calorie being the amount of heat absorbed in
raising 1 kilogramme of water 1 deg. C. Referring for a moment to what has
been said about specific heats, it will be apparent that if 1 large
calorie is sufficient to heat 1 kilo, of water through 1 deg. C. the same
quantity will heat 1 kilo.
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