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Gallium

 

Gallium is a soft, silver-white metal found throughout the
earth's crust. It was discovered in 1875 by the French
chemist, Paul Emile Lecoq de Boisbaudran ( 1838 - 1912 ).
He observed it while examining material separated from a
zinc blend. He then isolated the metal in 1876 and examined
its properties. The newly found element's properties were
the same as those predicted by Medeleyev for eka -
aluminum, an undiscovered element between aluminum and
indium on his periodic table. Boisbaudran called it gallium
in honor of France. ( Gallia is the Roman name for Gaul,
France ). 

Gallium ranks thirty-second in the order of abundance in
the Earth's crust. It is extracted as a by-product from
zinc blend, iron pyrites, bauxite, magnetite, kaolin and
germanite. 

Gallium is produced as a product of aluminum refining. It
is silvery white or blue-gray in color and soft enough to
be cut with a knife. It turns a bluish tint because of
superficial oxidation. Gallium is considered an unusual
element because of its low melting point ( 29.8 degrees
Celsius or 85.6 degrees Fahrenheit ). Its boiling point is
2,403 degrees Celsius. It expands when it becomes a solid,
cools quickly, and stays a liquid at temperatures as low as
0 degrees Celsius ( 32 degrees Fahrenheit ). Gallium is the
only metal other than mercury that stays a liquid at or
near room temperature. It is also used in high-temperature
thermometers because it remains in a liquid state over a
wide range of temperatures. Like water, it expands when
frozen. 

The liquid metal clings to glass and other similar
surfaces. It is stable in dry air. Gallium doesn't dissolve
in nitric acid because of a film of gallium oxide that
forms over it for protection. The metal does dissolve in
other acids to form gallium salt and gallates. Chemically,
gallium is similar to aluminum. It is amphetoric. It reacts
with sodium and potassium hydroxide solutions to result in
a gallate and hydrogen gas. Common compounds of gallium are
gallium chloride ( GaCl ), Gallium sulfide ( GaS ), gallium
sulfate ( GaSo ) and gallium oxide ( GaO ).
 
Gallium's uses were mostly experimental until the 1970's.
Gallium antinonide ( GaSb ) and gallium arsenide ( GaAs )
are used in electronic devices for voltage rectification
and amplification. Radioactive gallium could be helpful in
the study of bone cancer. As said earlier, it is used in
high-temperature thermometers and replaces amalgam in
dental fillings. Gallium can be used as a heat exchange for
nuclear reactors but since it corrodes most metals at high
temperatures, this idea has been discouraged.
 
Atomic number = 31
 
Atomic weight = 69.72
 
Melting point = 29.78 degrees Celsius
 
Boiling point = 2,403 degrees Celsius
 
Bibliography: 

" Gallium ". The New Encyclopedia Britannica, 1992 edition.
 
" Gallium ". The Universal Standard Encyclopedia, 1957
edition.
 
" Gallium ". Encyclopedia of Science and Technology, 1974
edition.
 
" Gallium ". Encyclopedia Americana, 1975 edition
 

 




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