unt absorbed during vaporization. (See
Laboratory Manual.)

We learn that the heat of vaporization is the same whether it is
considered as the heat absorbed by 1 gram of water in its change to
steam, or as the heat given out by 1 gram of steam during its
condensation into water.

24. Practical Application. We understand now the value of steam as a
heating agent. Water is heated in a boiler in the cellar, and the
steam passes through pipes which run to the various rooms; there the
steam condenses into water in the radiators, each gram of steam
setting free 536 calories of heat. When we consider the size of the
radiators and the large number of grams of steam which they contain,
and consider further that each gram in condensing sets free 536
calories, we understand the ease with which buildings are heated by
steam.

Most of us have at times profited by the heat of condensation. In cold
weather, when there is a roaring fire in the range, the water
frequently becomes so hot that it "steams" out of open faucets. If, at
such times, the hot water is turned on in a small cold bathroom, and
is allowed to run until the tub is well filled, vapor condenses on
windows, mirrors, and walls, and the cold room becomes perceptibly
warmer. The heat given out by the condensing steam passes into the
surrounding air and warms the room.

There is, however, another reason for the rise in temperature. If a
large pail of hot soup is placed in a larger pail of cold water, the
soup will gradually cool and the cold water will gradually become
warmer. A red-hot iron placed on a stand gradually cools, but warms
the stand. A hot body loses heat so long as a cooler body is near it;
the cold object is heated at the expense of the warmer object, and one
loses heat and the other gains heat until the temperature of both is
the same. Now the hot water in the tub gradually loses heat and the
cold air of the room gradually gains heat by convection, but the
amount given the room by convection is relatively small compared with
the large amount set free by the condensing steam.

25. Distillation. If impure, muddy water is boiled, drops of water
will collect on a cold plate held in the path of the steam, but the
drops will be clear and pure. When impure water is boiled, the steam
from it does not contain any of the impurities because these are left
behind in the vessel. If all the water were allowed to boil away, a
layer of mud or of other impurities would