49. The weight of air pressing on the surface of water
prevents the steam from escaping until it gains force enough
to overcome this pressure. At the sea level water boils
at exactly 212°, but on a high mountain at a temperature
several degrees lower. If the steam be confined, water may
be raised to several degrees above 212°; for the air under
the lid soon takes up all the vapor it can hold, making it
impossible for any more water to be changed into steam.
The heat that would otherwise be used in making steam is
now saved and makes the water hotter.
50. Real steam is invisible, the mist we call steam
being steam partially condensed. The slow forming of
water-vapor that takes place at ordinary temperatures,
in the drying of clothes, the disappearance of water
after a rain, and the like, is called evaporation.
51. Effect of cold on water. — At 32° F. water freezes,
becoming ice. At 32° ice melts, forming water. By
heating it, ice may be in a few minutes changed to
water, and from water to steam. Do you know of
anything else that is changed from solid to liquid, and
from liquid to gas, by heat ?
52. Solids, liquids, and gases. — The particles of which
a solid is composed hold firmly together, those of a liquid
hold loosely ; those of a gas tend always to go farther
apart. Heat separates particles of matter ; on cooling,
they draw together again. ^ Hence we say, "Heat
expands, cold contracts." Hot air rises, because by
expanding it becomes thinner and lighter.
1 Exception. — Water expands just before it freezes ; hence the
bursting of pipes.
30 THEORY AND PRACTICE OF COOKERY
53. Composition of water. — Water is composed of hydro-
gen and oxygen. In what experiment was water formed?
Where did the hydrogen come from ? The oxygen ? Water
may be decomposed by sodium, a soft white metal. A bit
of this thrown upon water unites with its oxygen so rapidly
as to catch fire. The hydrogen, ignited by this, burns also,
as is shown by the appearance of the blue hydrogen flame.
Some Facts about Water to be Remembered
54. 1. A solid dissolved in water Avill, in most cases,
be found at the bottom of the vessel after the water has
evaporated or boiled away.
2. Boiling expels air from water, making it taste
" flat." Boiled water should be poured back and forth
several times from one pitcher to another, or shaken in
a large bottle, to restore its flavor.
3. Hard water may be made soft by boiling.
4. Impure water may be made safe for use by boiling.
5. Since, by ordinary means, water cannot be made
hotter after it begins to boil, fuel is wasted iii keeping
up more fire than is required just to keep the water at the
hoiling-point.
6. By covering the vessel some of the steam is con-
densed, thereby saving heat.
55. Water in relation to health; drinking freely of
pure water makes for health. — The water we drink or
take in as part of our food aids digestion, conveys
nourishment to all parts of the body, removes waste,
and in other ways keeps the body in order. Large
quantities of cold water should not be drunk when one
PREPARATORY LESSONS 31
is overheated; nor should water or any other liquid
be used to wash down solid food.
Page 17
Presented as published in 1901. Historical recipes may not meet modern food-safety standards. Cook from the modern interpretation, not the original instructions.
AI-modernized reading of the original text
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49. The weight of air pressing on the surface of water
prevents the steam from escaping until it gains force enough
to overcome this pressure. At the sea level water boils
at exactly 212°, but on a high mountain at a temperature
several degrees lower. If the steam be confined, water may
be raised to several degrees above 212°; for the air under
the lid soon takes up all the vapor it can hold, making it
impossible for any more water to be changed into steam.
The heat that would otherwise be used in making steam is
now saved and makes the water hotter.
50. Real steam is invisible, the mist we call steam
being steam partially condensed. The slow forming of
water-vapor that takes place at ordinary temperatures,
in the drying of clothes, the disappearance of water
after a rain, and the like, is called evaporation.
51. Effect of cold on water. — At 32° F. water freezes,
becoming ice. At 32° ice melts, forming water. By
heating it, ice may be in a few minutes changed to
water, and from water to steam. Do you know of
anything else that is changed from solid to liquid, and
from liquid to gas, by heat ?
52. Solids, liquids, and gases. — The particles of which
a solid is composed hold firmly together, those of a liquid
hold loosely ; those of a gas tend always to go farther
apart. Heat separates particles of matter ; on cooling,
they draw together again. ^ Hence we say, "Heat
expands, cold contracts." Hot air rises, because by
expanding it becomes thinner and lighter.
1 Exception. — Water expands just before it freezes ; hence the
bursting of pipes.
30 THEORY AND PRACTICE OF COOKERY
53. Composition of water. — Water is composed of hydro-
gen and oxygen. In what experiment was water formed?
Where did the hydrogen come from ? The oxygen ? Water
may be decomposed by sodium, a soft white metal. A bit
of this thrown upon water unites with its oxygen so rapidly
as to catch fire. The hydrogen, ignited by this, burns also,
as is shown by the appearance of the blue hydrogen flame.
Some Facts about Water to be Remembered
54. 1. A solid dissolved in water Avill, in most cases,
be found at the bottom of the vessel after the water has
evaporated or boiled away.
2. Boiling expels air from water, making it taste
" flat." Boiled water should be poured back and forth
several times from one pitcher to another, or shaken in
a large bottle, to restore its flavor.
3. Hard water may be made soft by boiling.
4. Impure water may be made safe for use by boiling.
5. Since, by ordinary means, water cannot be made
hotter after it begins to boil, fuel is wasted iii keeping
up more fire than is required just to keep the water at the
hoiling-point.
6. By covering the vessel some of the steam is con-
densed, thereby saving heat.
55. Water in relation to health; drinking freely of
pure water makes for health. — The water we drink or
take in as part of our food aids digestion, conveys
nourishment to all parts of the body, removes waste,
and in other ways keeps the body in order. Large
quantities of cold water should not be drunk when one
PREPARATORY LESSONS 31
is overheated; nor should water or any other liquid
be used to wash down solid food.