What Is Oxygen?
Oxygen was discovered in 1774. It is an elementary substance in the form of a gas which is found free in the air. It is colorless, tasteless and odorless and, like hydrogen, cannot therefore be seen, tasted or smelled. It is soluble in water and combines very readily with most of the elements. In most cases when oxygen combines with other things the process of combining is so rapid that light and heat are produced—this combination is called combustion. Where the process of combining with other substances acts slowly the heat and light produced at one time are not enough to be noticed. Where metals tarnish or rust or animal or vegetable substances decay, the same thing chemically is taking place as when you light a fire and produce light or heat—you are making the oxygen combine with the substance in the material which is burning. When iron is rusting or vegetables decaying, the action is so slow that no heat or light is produced, but the result is the same if some outside force does not stop the action. The fire will burn until everything burnable which it can reach is burned out, and in the case of the piece of iron rusting, the action will go on slowly until the whole piece of iron is destroyed—or burned out. Like hydrogen, no vegetable or animal life can live without oxygen continually given it. Oxygen will destroy life and will sustain it.
All of our body heat and muscular energy are produced by slow combustion going on in all parts of the body, of oxygen carried in the blood after it enters the lungs. In sunlight oxygen is exhaled by growing plants.
Oxygen is the most widely distributed and abundant element in nature. It amounts to about one-fifth of the volume of the air belt of the earth; about ninety per cent of all the weight of water is oxygen. The rocks of the earth contain about fifty per cent of oxygen and it is found in most animal and vegetable products and in acids.