evaporating a pound of water at 212 degrees to steam at
212 degrees, 897.6 B. t. u. are expended as internal latent heat and
72.8 B. t. u. as external latent heat. For a more detailed description
of the changes brought about in water by sensible and latent heat, the
reader is again referred to the chapter on "The Theory of Steam Making".

Ebullition--The temperature of ebullition of any liquid, or its boiling
point, may be defined as the temperature which exists where the addition
of heat to the liquid no longer increases its temperature, the heat
added being absorbed or utilized in converting the liquid into vapor.
This temperature is dependent upon the pressure under which the liquid
is evaporated, being higher as the pressure is greater.

TABLE 5

BOILING POINTS AT ATMOSPHERIC PRESSURE

+---------------------+--------------+
| | Degrees |
| | Fahrenheit |
+---------------------+--------------+
| Ammonia | 140 |
| Bromine | 145 |
| Alcohol | 173 |
| Benzine | 212 |
| Water | 212 |
| Average Sea Water | 213.2 |
| Saturated Brine | 226 |
| Mercury | 680 |
+---------------------+--------------+

Total Heat of Evaporation--The quantity of heat required to raise a unit
of any liquid from the freezing point to any given temperature, and to
entirely evaporate it at that temperature, is the total heat of
evaporation of the liquid for that temperature. It is the sum of the
heat of the liquid and the latent heat of evaporation.

To recapitulate, the heat added to a body is divided as follows:

Total heat = Heat to change the temperature + heat to overcome the
molecular cohesion + heat to overcome the external pressure
resisting an increase of volume of the body.

Where water is converted into steam, this total heat is divided as
follows:

Total heat = Heat to change the temperature of the water + heat to
separate the molecules of the water + heat to overcome
resistance to increase in volume of the steam,
= Heat of the liquid + internal latent heat + external
latent heat,
= Heat of the liquid + total latent heat of steam,
= Total heat of evaporation.

The steam tables given on pages 122 to 127 give the heat