Blow a candle out; and while the wick is still red, hold the candle (by a piece of wire,) in the bottle of oxygen gas; the wick will instantly ignite, and burn brilliantly.
(Burning sulphur emits a blue flame, when immersed in oxygen gas.)
Q. What is nitrogen?
A. Nitrogen is another invisible gas. It will not burn, like hydrogen; and an animal cannot live in it: it abounds in animal and vegetable substances, and is the chief ingredient of the common air.[9]
[9] Nitrogen gas may easily be obtained thus:—Put a piece of burning phosphorus on a little stand, in a plate of water; and cover a bell glass over. (Be sure the edge of the glass stands in the water.) In a few minutes the air will be decomposed, and nitrogen alone remain in the bell glass.
(N.B. The white fume which will arise and be absorbed by the water in this experiment, is phosphoric acid; i. e. phosphorus combined with oxygen of the air.)
Q. Why is there so much nitrogen in the air?
A. In order to dilute the oxygen. If the oxygen were not thus diluted, fires would burn out, and life would be exhausted too quickly.
Q. What three elements are necessary to produce combustion?
A. Hydrogen gas, carbon, and oxygen gas; the two former in the fuel, and the last in the air which surrounds the fuel.