Water
boils when the bubbles thus rise to the surface, and steam is thrown
off. If the temperature is now tested, it will be found to be about
212 deg. F. When water begins to boil, it is impossible to increase its
temperature, as the steam carries off the heat as rapidly as it is
communicated to the water. The only way in which the temperature can be
raised, is by the confinement of the steam; but owing to its enormous
expansive force, this is not practicable with ordinary cooking utensils.
The mechanical action of the water is increased by rapid bubbling, but
not the heat; and to boil anything violently does not expedite the
cooking process, save that by the mechanical action of the water the
food is broken into smaller pieces, which are for this reason more
readily softened. But violent boiling occasions an enormous waste of
fuel, and by driving away in the steam the volatile and savory elements
of the food, renders it much less palatable, if not altogether
tasteless. The solvent properties of water are so increased by heat that
it permeates the food, rendering its hard and tough constituents soft
and easy of digestion.

The liquids mostly employed in the cooking of foods are water and milk.
Water is best suited for the cooking of most foods, but for such
farinaceous foods as rice, macaroni, and farina, milk, or at least part
milk, is preferable, as it adds to their nutritive value. In using milk
for cooking purposes, it should be remembered that being more dense than
water, when heated, less steam escapes, and consequently it boils sooner
than does water. Then, too, milk being more dense, when it is used alone
for cooking, a little larger quantity of fluid will be required than
when water is used.

The boiling point for water at the sea level is 212 deg. At all points
above the sea level, water boils at a temperature below 212 deg., the exact
temperature depending upon the altitude. At the top of Mt. Blanc, an
altitude of 15,000 feet, water boils at 185 deg. The boiling point is
lowered one degree for every 600 feet increase in altitude. The boiling
point may be increased by adding soluble substances to the water. A
saturated solution of common baking soda boils at 220 deg. A saturated
solution of chloride of sodium boils at 227 deg. A similar solution of
sal-ammoniac boils at 238 deg. Of course such solutions cannot be used
advantageously, except as a means of cooking articles placed in
hermetically sealed vessel