Julie Shafter, age 13, of Burlington, Vt., for her question:
WHO DISCOVERED NITROGEN?
Nitrogen is the chief gas in the air. It makes up about 75 percent of all the air by weight, and about 79 percent by volume. Almost all of the rest of the air is oxygen.
Nitrogen was discovered in 1772 by a Scottish physician named Daniel Rutherford.
Nitrogen is one of the substances that is absolutely necessary for life. It is found in protoplasm, the living material in plants and animal tissues. It is also part of all protein foods.
Nitrogen is one of the nonmetal chemical elements. The gas is colorless, tasteless and odorless. Pure nitrogen is a little lighter than air and 14 times as heavy as hydrogen, the lightest of all known elements.
In the air, nitrogen dilutes the oxygen, so combustion in air is slower than in pure oxygen. Also, nitrogen is not very soluble in water and does not combine easily with other elements.
We receive our nitrogen by eating plant or animal food that contains compounds of the element. But any nitrogen in the animal food really comes from plants.
When animals breathe, they draw nitrogen and oxygen into their lungs. Only the oxygen unites with the blood. Some nitrogen dissolves in the blood, but most of it is breathed out again.
Most plants get nitrogen from soluble nitrogen compounds in the soil. Nitrogen in the soil may come from the atmosphere, with the help of lightning and rain. The action of electricity in the air causes oxygen and nitrogen to form oxides of nitrogen. Then the rain carries these oxides into the soil.
If the soil is in use, the rain does not supply enough nitrogen to keep it rich. Thus, farmers have to renew the nitrogen in their fields by rotating their crops, or by using nitrogenous fertilizers.
In crop rotation, plants which consume nitrogen are followed by plants which restore it. Wheat and corn take nitrogen from the soil, while clover, beans and other legumes return nitrogen.
Borazon, an artificially produced crystal with the hardness of a diamond, is a compound of nitrogen and boron.
Ammonia is a compound of nitrogen and hydrogen. Ammonia is used to make nitric acid, an ingredient of TNT and other high powered explosives. This important acid is a combination compound of the elements nitrogen, hydrogen and oxygen.
There are five oxides of nitrogen. Nitrous oxide is the "laughing gas" which is used as an anesthetic. Nitric oxide is used to carry oxygen in the manufacture of sulfuric acid. Nitrogen trioxide, nitrogen peroxide and nitrogen pentoxide are oxidizing agents.
Liquid nitrogen is used as a cooling agent. It is also used as a pulverizing agent.
Automobile engines also produce nitrogen oxides. These oxides contribute to air pollution.