If we remove the oxygen from air, what remains is chiefly nitrogen. While other substances are present in small quantities, the nitrogen will be sufficiently pure for study.
Nitrogen is a gas that has neither color nor odor. It will not burn, nor will substances burn in it. Nitrogen is known as an inert gas. An inert, or inactive, substance is one that does not readily combine with other substances, as oxygen does. When animals and plants breathe, nitrogen enters their bodies, along with the rest of the air, but it passes out again without being changed. Yet it makes life possible because without it in the air the percentages of both oxygen and carbon dioxide would probably be too great for use by living things.
Thus nitrogen dilutes, the oxygen and carbon dioxide of the air. Nitrogen is also supremely important as a necessary part of many food substances that are required by both plants and animals.