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Nitrogen

Nitrogen was isolated by the British physician
Daniel Rutherford in 1772 and recognized as an
elemental gas by the French chemist Antoine
Laurent Lavoisier about 1776. Properties
Nitrogen is a colorless, odorless, tasteless,
nontoxic gas. It can be condensed into a colorless
liquid, which can in turn be compressed into a
colorless, crystalline solid. Nitrogen exists in two
natural forms of isotopes, and four radioactive
isotopes have been artificially prepared. Nitrogen
melts at -210.01° C (-346.02° F), boils at
-195.79° C (-320.42° F), and has a density of
1.251 g/liter at 0° C (32° F). The atomic weight of
nitrogen is 14.007. Nitrogen is obtained from the
atmosphere by passing air over heated copper or
iron. The oxygen is removed from the air, leaving
nitrogen mixed with some inert gases. Pure
nitrogen is obtained by partial evaporation of liquid
air because liquid nitrogen has a lower boiling
point than liquid oxygen, the nitrogen evaporates
off first and can be collected. Nitrogen composes
about four-fifths (78.03 percent) by volume of the
atmosphere. Nitrogen is inert and serves as a
diluent for oxygen in burning and respiration
processes. It is an important element in plant
nutrition certain bacteria in the soil convert
nitrogen from the atmosphere into a form, such as
nitrate, that can be absorbed by plants, a process
called nitrogen fixation. Nitrogen in the form of
protein is an important component of animal tissue.
The element occurs in the combined state in
minerals, of which saltpeter (KNO3) and Chile
saltpeter (NaNO3) are highly important products.
Nitrogen combines with other elements only at
very high temperatures or pressures. It is
converted to an active form by passing through an
electric discharge at low pressure. The nitrogen
produced is very active, combining with alkali
metals to form azides with the vapor of zinc,
mercury cadmium, and arsenic to form nitrides and
with many hydrocarbons to form nitriles....