AIR
CONSTITUENTS OF AIR
Air is a mixture of gases, not a chemical compound, which envelops the earth and it is estimated to be at least one hundred miles high. This gaseous envelope is known as the atmosphere. The water upon the earth’s surface is called the aquasphere. The solid substance composing the earth is known as the petrosphere.
Air performs a very important function in the interchanging of gases in respiration and in the regulation of bodily temperature. The gases contained in the atmosphere are given by most authorities in the following proportions, per volume:
| Oxygen | 20.93% |
| Nitrogen | 78.10% |
| Argon | 0.94% |
| Carbon Dioxide | 0.03% |
With traces of helium, krypton, neon, xenon, hydrogen, ammonia, ozone and hydrogen peroxide.
It is also found that there is a varying amount of water in the air, as well as dust and other substances. It is worthy of note that the air maintains a wonderful uniformity of composition over the entire surface of the earth. This is undoubtedly due to the fact that the atmosphere is in constant motion which maintains its proper mixture. It must also be noted that the air is not a chemical compound but is a mixture of gases.
Oxygen (O)
Probably the most important element in air is the oxygen which represents about one-fifth of its composition. This percentage is maintained with very slight variation; for instance, the percentage of oxygen in towns will be slightly less than 20.93%, about 20.87%.
When the atmosphere contains only 11% or 12% of oxygen it becomes dangerous, and death results when the percentage gets as low as 7.2%. A candle will not burn with the oxygen at 16%. Slight variation in the amount of oxygen is of no special importance.