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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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