What is the nature of oxygen?

In many respects oxygen is the part of the air which concerns us most. Unlike the other gases of the air, oxygen is a very active substance. That is, it is the only one of the atmospheric gases which combines readily with other substances to form new substances.

When we breathe, we take in all the substances composing the air, but we make direct use of oxygen only. So far as we know, nitrogen and the other gases which usually are part of the air are neither harmful’ nor useful to us. The dust may be harmful, as will be shown later. Sometimes such a harmful gas as carbon monoxide may become mixed with the air. Or substances which we can smell may be in the air.

Since oxygen cannot be seen, we must learn about it by other means. Oxygen can be secured by separating it from the other substances composing the air, but it is more easily secured in other ways. Certain substances which contain oxygen may be changed in such a way that the oxygen is set free. It may be caught in glass tubes or other vessels and then examined.

A common substance for this use is potassium chlorate. This is a white substance which is sometimes used as a medicine for sore throat.