have become latent, and represent the heat of liquefaction of 1 kilogram
of ice. Had we mixed 1 kilogram of water at 0° C. with 1 kilogram of
water at 79° C. there would have been no change of state, and the
temperature of the mixture might be represented as a distribution of the
79° C. through the whole mass of the 2 kilograms, and so would be
39-1/2° C. We say, therefore, the latent heat of water is the heat which
is absorbed or rendered latent when a unit of weight, say 1 kilogram of
water as ice, melts and liquefies to a unit of water at zero, or it is
79 heat units. These 79 units of heat would raise 79 units of weight of
liquid water through 1° C., or one unit of liquid water through 79°.

Let us now inquire what the latent heat of steam is. If we take 1
kilogram of water at 0° C. and blow steam from boiling water at 100° C.
into it until the water just boils, and then stop and weigh the
resulting water, we shall find it amounts to 1·187 kilograms, so that
0·187 kilogram of water which was in the gaseous steam form, and had
besides a sensible heat of 100° C., has changed its state to that of
liquid water. This liquid water, being at the boiling-point, has still
the 100° C. of sensible heat, and hence the water in the gaseous steam
form can have given up to the water at 0° C. into which it was blown,
only the latent heat of gasification which was not sensible, but by
virtue of which it was enabled to assume the gaseous form. But if 0·187
kilogram of steam at 100° C. can heat 1 kilogram of water through 100
degrees, then 1 kilogram of steam can raise 5·36 kilograms of ice-cold
water through 100 degrees, or 536 kilograms through 1 degree, and thus
the latent heat of steam is 536 heat units.

_Effect of Increase of Pressure on the Boiling of Water._--Now we have
referred to diminution of pressure and its effect on the boiling-point
of water, and I may point out that by increasing the pressure, such,