illaries^ and at the same time carbon dioxide, brought
by the blood from all over the body, passes out into the
air. The blood flows on to other parts of the body,
giving up oxygen on its way, thus literally keeping up
the " fires of life " ; for without oxygen life would go
out as surely as does the burning splinter. Carbon
dioxide, on the contrary, is useless, — a substance to be
carried off by the blood, and quickly gotten rid of
through the lungs.
6. Plants breathe through their leaves^ taking in car-
bon dioxide and giving off oxygen when in the sunlight.
At other times they give off carbon dioxide.
AIR IN ITS RELATION TO FIRE
7. Food being cooked chiefly by means of heat,
cookery includes a study of fire. Let us learn what
we can of the relation of air to fire.
A Study of Combustion
8. Experiments with a candle. — A. Set a two-inch piece of
candle on the table and light it. How does it burn ? Notice the
appearance of the flame. (Fig. 1, a.)
B. Set over the candle a lamp-chimney supported on two pencils
or blocks of wood. (Fig. 1,6.) Notice how the flame has changed.
Hold your hand for a moment about two inches above the chim-
ney, and notice the heat felt. Hold a bit of tissue paper just above
the chimney. Is it drawn upward or downward? Hold it near
the space at the base of the chimney. Is it drawn outward or
inward?
C. Remove the^ supports, letting the chimney rest upon the
table. (Fig. 1, c.) Test for heat with your hand, then hold the
8
THEORY AND PRACTICE OF COOKERY
bit of paper as before. Do you feel any heat? Does the paper
move? What happens to the candle? Can you, by recalling the
experiment with the splinter and the bottle, explain this ?
D. Relight the candle, replace the chimney upon the supports,
and cover the top with a piece of thick cardboard. (Fig. 1, d.)
What happens? Explain. Removing the cardboard, quickly
thrust a lighted splinter inside of the chimney. What gas do you
think may be present ?
E. Through a tiny hole in the cardboard pass a fine wire bent
into a small loop at one end. Arrange candle and chimney as in
Exp. D. Dip the wire loop into clear lime-water, which should
form a film across the loop. Cover the chimney with the card-
board, letting the wire hang inside. (Fig. 1, e.) About two
minutes after the candle goes out examine the film. What gas
has been formed ? Is the candle as large as it was before it was
lighted? W^hat has become of the part that has disappeared?
9. Explanation of the burning of a candle. — When a
candle is lighted, the wax, by the heat of the burning
match, is first melted, and then, being soaked up by the
wick, is changed to gas. The oxygen of the air, always
eager for something to unite with, seizes upon this gas;
PREPARATORY LESSONS 9
in other words, the gns hums. Whenever oxygen
unites with another substance so rapidly that light and
heat are given off, we have burning, or combustion. The
light and heat we call fire. Flame is burning yas.
Page 7
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.
illaries^ and at the same time carbon dioxide, brought
by the blood from all over the body, passes out into the
air. The blood flows on to other parts of the body,
giving up oxygen on its way, thus literally keeping up
the " fires of life " ; for without oxygen life would go
out as surely as does the burning splinter. Carbon
dioxide, on the contrary, is useless, — a substance to be
carried off by the blood, and quickly gotten rid of
through the lungs.
6. Plants breathe through their leaves^ taking in car-
bon dioxide and giving off oxygen when in the sunlight.
At other times they give off carbon dioxide.
AIR IN ITS RELATION TO FIRE
7. Food being cooked chiefly by means of heat,
cookery includes a study of fire. Let us learn what
we can of the relation of air to fire.
A Study of Combustion
8. Experiments with a candle. — A. Set a two-inch piece of
candle on the table and light it. How does it burn ? Notice the
appearance of the flame. (Fig. 1, a.)
B. Set over the candle a lamp-chimney supported on two pencils
or blocks of wood. (Fig. 1,6.) Notice how the flame has changed.
Hold your hand for a moment about two inches above the chim-
ney, and notice the heat felt. Hold a bit of tissue paper just above
the chimney. Is it drawn upward or downward? Hold it near
the space at the base of the chimney. Is it drawn outward or
inward?
C. Remove the^ supports, letting the chimney rest upon the
table. (Fig. 1, c.) Test for heat with your hand, then hold the
8
THEORY AND PRACTICE OF COOKERY
bit of paper as before. Do you feel any heat? Does the paper
move? What happens to the candle? Can you, by recalling the
experiment with the splinter and the bottle, explain this ?
D. Relight the candle, replace the chimney upon the supports,
and cover the top with a piece of thick cardboard. (Fig. 1, d.)
What happens? Explain. Removing the cardboard, quickly
thrust a lighted splinter inside of the chimney. What gas do you
think may be present ?
E. Through a tiny hole in the cardboard pass a fine wire bent
into a small loop at one end. Arrange candle and chimney as in
Exp. D. Dip the wire loop into clear lime-water, which should
form a film across the loop. Cover the chimney with the card-
board, letting the wire hang inside. (Fig. 1, e.) About two
minutes after the candle goes out examine the film. What gas
has been formed ? Is the candle as large as it was before it was
lighted? W^hat has become of the part that has disappeared?
9. Explanation of the burning of a candle. — When a
candle is lighted, the wax, by the heat of the burning
match, is first melted, and then, being soaked up by the
wick, is changed to gas. The oxygen of the air, always
eager for something to unite with, seizes upon this gas;
PREPARATORY LESSONS 9
in other words, the gns hums. Whenever oxygen
unites with another substance so rapidly that light and
heat are given off, we have burning, or combustion. The
light and heat we call fire. Flame is burning yas.