of exerting any of the following effects. It is sufficient (1) to raise
1000 grammes of water through 28 deg. C., say from 10 deg. C. (50 deg. F.,
which is roughly the temperature of ordinary cold water) to 38 deg. C. It
is sufficient (2) to raise 64 grammes of water (a weight equal to that of
the carbide decomposed) through 438 deg. C., if that were possible. It would
raise (3) 311 grammes of water through 90 deg. C., _i.e._, from 10 deg. C.
to the boiling-point. If, however, instead of remaining in the liquid state,
the water were converted into vapour, the same quantity of heat would
suffice (4) to change 44.7 grammes of water at 10 deg. C. into steam at
100 deg. C.; or (5) to change 46.7 grammes of water at 10 deg. C. into
vapour at the same temperature. It is an action of the last character which
takes place in acetylene generators of the most modern and usual pattern,
some of the surplus water being evaporated and carried away as vapour at a
comparatively low temperature with the escaping gas; for it must be
remembered that although steam, as such, condenses into liquid water
immediately the surrounding temperature falls below 100 deg. C., the vapour
of water remains uncondensed, even at temperatures below the freezing-
point, when that vapour is distributed among some permanent gas--the
precise quantity of vapour so remaining being a function of the
temperature and barometric height. Thus it appears that if the heat
evolved during the decomposition of calcium carbide is not otherwise
consumed, it is sufficient in amount to vaporise almost exactly 3 parts
by weight of water for every 4 parts of carbide attacked; but if it were
expended upon some substance such as acetylene, calcium carbide, or
steel, which, unlike water, could not absorb an extra amount by changing
its physical state (from solid to liquid, or from liquid to gas), the
heat generated during the decomposition of a given weight of carbide
would suffice to raise an equal weight of the particular substance under
consideration to a temperature vastly exceeding 438 deg. C. The temperature
attained, indeed, measured in Centigrade degrees, would be 438 multiplied