filtered through sand beds. Filters of charcoal or porce-
lain for household use must be kept clean, or they soon
become filled with impurities, making the water passed
through them fouler instead of purer. Small filters
screwed on to faucets are of little or no value. Drinking
water about the purity of which there is any doubt
should be boiled to kill germs (bacteria^. (§§ 57-59.)
Water may dissolve lead from the pipes it runs through.
To avoid the risk of lead poisoning, let the water run
for a few minutes — long enough for what has stood in
the pipes over night to run off — before drawing any
for use.
A Study of the Effect of Heat on Water
47. Experiment. — Put some water in a saucepan or other ves-
sel. Take its temperature with a thermometer. Set it on the stove
or over a Bunsen burner, and
hold the thermometer so that
its bulb is below the surface of
the water, but not touching the
bottom of the vessel. (Fig. 4.)
Watch the sides and bottom of
the saucepan.
Are the bubbles large or
small at first? After a little
while? AVhat comes off from
the surface of the water ? Note
the temperature of the water.
Note it again when the bubbles
begin to break at the, surface.
Does the mercury rise after this?
Increase the heat. Can you
make the water any hotter?
Fig. 4.
28 THEORY AND PRACTICE OF COOKERY
48. The changing of water into steam ; simmering-point
of water 185° F. ; boiling-point 212° F. — When water is
heated the air dissolved in it expands, forming tiny
bubbles. These rise, but the cold water near the sur-
face chilling them, they contract, and sink again. When
all the water has become warm they rise and escape.
By this time the heat is beginning to change the water
into steam, an invisible gas. The steam bubbles are
larger than the air bubbles. As they near the surface
of the water, they are cooled, and condensed, i.e. turned
back to water. This bubbling below the surface is
called simmering. ^ The temperature of the water is
now about 185° F. The water growing hotter, some of
the bubbles reach the surface and break there, giving
oiT clouds of steam. Now, for the first time, the
Avater boils. Its temperature is 212° F. By increasing
the heat the water may be made to boil faster, but it
will not grow hotter. All the heat is now being used
in turning water into steam. If boiled long enough all
the water turns to steam and disappears in the air.
If steam be cooled, by coming against a cover, for
instance, it gives up its heat and becomes water
again.
The word vapor is applied to gases that, under ordi-
nary circumstances, are liquid. Steam, therefore, is
water-vapor.
1 In cooking, it is sometimes important to keep water simmering ;
at other times necessary to have it boiling. Learn to distinguish
between these, When steam comes in jets from the spout of a tea-
kettle, the water boils.
PREPARATORY LESSONS 29
Page 16
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
A modernized reading is not available for this page yet. You are seeing the original text.
filtered through sand beds. Filters of charcoal or porce-
lain for household use must be kept clean, or they soon
become filled with impurities, making the water passed
through them fouler instead of purer. Small filters
screwed on to faucets are of little or no value. Drinking
water about the purity of which there is any doubt
should be boiled to kill germs (bacteria^. (§§ 57-59.)
Water may dissolve lead from the pipes it runs through.
To avoid the risk of lead poisoning, let the water run
for a few minutes — long enough for what has stood in
the pipes over night to run off — before drawing any
for use.
A Study of the Effect of Heat on Water
47. Experiment. — Put some water in a saucepan or other ves-
sel. Take its temperature with a thermometer. Set it on the stove
or over a Bunsen burner, and
hold the thermometer so that
its bulb is below the surface of
the water, but not touching the
bottom of the vessel. (Fig. 4.)
Watch the sides and bottom of
the saucepan.
Are the bubbles large or
small at first? After a little
while? AVhat comes off from
the surface of the water ? Note
the temperature of the water.
Note it again when the bubbles
begin to break at the, surface.
Does the mercury rise after this?
Increase the heat. Can you
make the water any hotter?
Fig. 4.
28 THEORY AND PRACTICE OF COOKERY
48. The changing of water into steam ; simmering-point
of water 185° F. ; boiling-point 212° F. — When water is
heated the air dissolved in it expands, forming tiny
bubbles. These rise, but the cold water near the sur-
face chilling them, they contract, and sink again. When
all the water has become warm they rise and escape.
By this time the heat is beginning to change the water
into steam, an invisible gas. The steam bubbles are
larger than the air bubbles. As they near the surface
of the water, they are cooled, and condensed, i.e. turned
back to water. This bubbling below the surface is
called simmering. ^ The temperature of the water is
now about 185° F. The water growing hotter, some of
the bubbles reach the surface and break there, giving
oiT clouds of steam. Now, for the first time, the
Avater boils. Its temperature is 212° F. By increasing
the heat the water may be made to boil faster, but it
will not grow hotter. All the heat is now being used
in turning water into steam. If boiled long enough all
the water turns to steam and disappears in the air.
If steam be cooled, by coming against a cover, for
instance, it gives up its heat and becomes water
again.
The word vapor is applied to gases that, under ordi-
nary circumstances, are liquid. Steam, therefore, is
water-vapor.
1 In cooking, it is sometimes important to keep water simmering ;
at other times necessary to have it boiling. Learn to distinguish
between these, When steam comes in jets from the spout of a tea-
kettle, the water boils.
PREPARATORY LESSONS 29