is oxygen and four-jfiftlis nitrogen. Small amounts of other
substances are always present. The nitrogen is very inert
and neither affects the body nor is affected by it. The
oxygen is the part of the air which is essential to life and
health. Oxygen is frequently called the supporter of com-
bustion. When a substance burns, it unites with oxygen
and a compound is formed, which, while it contains both
the substance itself and oxygen, is unlike either. Such
a compound, called an oxide, will not burn because it has
already all the oxygen it can hold. Neither is it a good
supporter of combustion, because oxygen will not ordinarily
leave the substance which holds it to unite with a new
substance.
The oxygen in the air which enters our lungs is carried
by the blood to the various tissues of the body. It there
unites with the substances which compose the tissues.
This phenomenon is called burning, and serves the double
purpose of changing worn-out tissue into substances which
can be easily removed from the body, and of maintaining
animal heat. As the tissues are largely composed of carbon
and hydrogen, the substances formed in the burning are
chiefly oxides of carbon and of hydrogen. The former is a
gas known as carbon dioxide. The latter is water. These
are brought by the blood to the lungs and there excreted
from the body. As they do not support combustion, it is
useless to breathe them into the lungs. The process of
breathing, therefore, carried on in a closed room, is con-
stantly removing from the air a substance which is useful
to the body, and returning to it substances which are
useless. Worse than this, we are constantly breathing off
minute particles of poisonous substances, probably bits of
worn-out lung tissue. These substances are known as
" crowd-poisoning," and give the bad odor to closed rooms
in which many people are breathing.
266 HANDBOOK OF DOMESTIC SCIENCE
It is evident, then, that in a bedroom, in which one
remains so many hours out of the twenty-four, there should
be a constant supply of fresh air. If fresh air is not sup-
plied, the impure air is breathed oyer and over again, and
both the carbon dioxide, which is useless, and the " crowd-
poisoning," which is extremely harmful, constantly increase,
while the useful oxygen diminishes. Nor is it safe to make
one's senses the test of the purity of the air which he has for
some time been breathing. It is easy to become accustomed
to bad air. Who has not entered a close room, and found it
difficult to breathe the air, whose impurity the occupants of
the room had not discovered ?
Experiments. I. To sliow that oxygen supports combus-
tion. — In a test-tube heat a few pieces of potassium chlorate
until gas is given off. This gas is oxygen. Light a match.
Extinguish all but a spark. Insert in gas at top of the tube.
It bursts into a flame.
Note. — By consulting the works on chemistry given as references,
the teacher can learn methods of preparing oxygen on a larger scale,
and can show its properties more in detail,
Page 127
Presented as published in 1900. 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
is oxygen and four-fifths nitrogen. Small amounts of other substances are always present. The nitrogen is very inert and neither affects the body nor is affected by it. The oxygen is the part of the air which is essential to life and health. Oxygen is frequently called the supporter of combustion. When a substance burns, it unites with oxygen and a compound is formed, which, while it contains both the substance itself and oxygen, is unlike either. Such a compound, called an oxide, will not burn because it has already all the oxygen it can hold. Neither is it a good supporter of combustion, because oxygen will not ordinarily leave the substance which holds it to unite with a new substance.
The oxygen in the air which enters our lungs is carried by the blood to the various tissues of the body. It there unites with the substances which compose the tissues. This phenomenon is called burning, and serves the double purpose of changing worn-out tissue into substances which can be easily removed from the body, and of maintaining animal heat. As the tissues are largely composed of carbon and hydrogen, the substances formed in the burning are chiefly oxides of carbon and of hydrogen. The former is a gas known as carbon dioxide. The latter is water. These are brought by the blood to the lungs and there excreted from the body. As they do not support combustion, it is useless to breathe them into the lungs. The process of breathing, therefore, carried on in a closed room, is constantly removing from the air a substance which is useful to the body, and returning to it substances which are useless. Worse than this, we are constantly breathing off minute particles of poisonous substances, probably bits of worn-out lung tissue. These substances are known as " crowd-poisoning," and give the bad odor to closed rooms in which many people are breathing.
It is evident, then, that in a bedroom, in which one remains so many hours out of the twenty-four, there should be a constant supply of fresh air. If fresh air is not supplied, the impure air is breathed oyer and over again, and both the carbon dioxide, which is useless, and the " crowdpoisoning," which is extremely harmful, constantly increase, while the useful oxygen diminishes. Nor is it safe to make one's senses the test of the purity of the air which he has for some time been breathing. It is easy to become accustomed to bad air. Who has not entered a close room, and found it difficult to breathe the air, whose impurity the occupants of the room had not discovered ?
Experiments. I. To sliow that oxygen supports combustion. — In a test-tube heat a few pieces of potassium chlorate until gas is given off. This gas is oxygen. Light a match. Extinguish all but a spark. Insert in gas at top of the tube. It bursts into a flame.
Note. — By consulting the works on chemistry given as references, the teacher can learn methods of preparing oxygen on a larger scale, and can show its properties more in detail,