The
specific heat of calcium carbide is also comparatively small, and there
are similar disadvantages in allowing it to become hot; moreover it is
deficient in heat-conducting power, so that heat communicated to one
portion of the mass does not extend rapidly throughout, but remains
concentrated in one spot, causing the temperature to rise objectionably.
Steel has a sufficient amount of heat-conducting power to prevent undue
concentration in one place; but, as has been stated, its specific heat is
only one-ninth that of water. Water is clearly, therefore, the proper
substance to employ for the dissipation of the heat generated, although
it is strictly speaking almost devoid of heat-conducting power; for not
only is the specific heat of water much greater than that of any other
material present, but it possesses in a high degree the faculty of
absorbing heat throughout its mass, by virtue of the action known as
convection, provided that heat is communicated to it at or near the
bottom, and not too near its upper surface. Moreover, water is a much
more valuable substance for dissipating heat than appears from the
foregoing explanation; for reference to the experiment with the gas-
burner will show that six and a quarter times as much heat can be
absorbed by a given weight of water if it is permitted to change into
steam, as if it is merely raised to the boiling-point; and since by no
urging of the gas-burner can the temperature be raised above 100 deg.
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