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The properties
of oxygen are as follows: its
atomic weight is
15.9994; at atmospheric pressure, the element boils at -182.96° C
(-297.33° F) and melts at -218.4° C (-361.1° F); it has a density of
1.429 grams/liter at 0° C (32° F).
There are three
known forms of oxygen namely, ordinary oxygen (O2) which
contains two atoms per molecule; ozone (O3), containing
three atoms per molecule; and a pale blue, non magnetic form, (O4),
containing four atoms per molecule, which readily breaks down into
ordinary oxygen.
Oxygen is
prepared in the laboratory from salts such as potassium chlorate,
barium peroxide and sodium peroxide. Electrolysis of water and the
fractional distillation of liquid air are the two most important
methods for the preparation of oxygen in the industry. In the latter
method, air is liquefied and allowed to evaporate. The nitrogen in
the liquid air is more volatile and boils off first, leaving the
oxygen.
The gas is stored
and shipped in either liquid or gaseous form. Gaseous oxygen can be
condensed to a pale blue liquid that is strongly magnetic. When the
liquid is compressed, pale blue solid oxygen is produced.
Oxygen is a
component of many organic and inorganic compounds. It forms
compounds called oxides with almost all the elements,
including some of the noble gases. A chemical reaction in which an
oxide forms is called oxidation.
There are many
uses of oxygen. Large amounts of the gas are used in
high-temperature welding torches, in which a mixture of oxygen and
another gas produces a flame of much higher temperature than is
obtained by burning gases in air. Oxygen is administered to patients
whose breathing is impaired. It is also administered to people in
aircrafts flying at high altitudes, where the poor oxygen
concentration cannot support normal respiration. Oxygen-enriched air
is used in open-hearth furnaces for steel manufacture.
Most of the
oxygen produced in the United States is used to make a mixture of
carbon monoxide and hydrogen called “synthesis gas”, used for
the synthesis of methanol and ammonia. High-purity oxygen is used in
metal fabrication industries. Liquid oxygen is used as a propellant
for guided missiles and rockets. |
