(lat.)chem. Element, Zeichen Al, Ordnungszahl 13, Atommasse 26,98, ein silberglänzendes Leichtmetall, Dichte 2,699 g/cm?. A. wird aus Tonerde, die aus Bauxit gewonnen wird, in Elektrolyseöfen erschmolzen und zu Blechen, Platten, Folien, Rohrleitungen, Kabeln u.a. verarbeitet. Der hohe Energieaufwand bei der A.schmelze wird durch weitgehendes Recycling von Alt-A. kompensiert.
ETYM Latin alumen. Related to Alum.
The metallic base of alumina. The metal is white, but with a bluish tinge, and is remarkable for its resistance to oxidation, and for its lightness, pertaining a specific gravity of about 2.6. Atomic weight 27.08. Symbol Al.
Light, malleable white metal, resistant to organic salts, obtained by heating aluminum oxide.
Lightweight, silver-white, ductile and malleable, metallic element, symbol Al, atomic number 13, atomic weight 26.9815, melting point 658şC. It is the third most abundant element (and the most abundant metal) in the Earth's crust, of which it makes up about 8.1% by mass. It oxidizes rapidly, the layer of oxide on its surface making it highly resistant to tarnish, and is an excellent conductor of electricity. In its pure state aluminum is a weak metal, but when combined with elements such as copper, silicon, or magnesium it forms alloys of great strength. In nature it is found only in the combined state in many minerals, and is prepared commercially from the ore bauxite.
Aluminum is a reactive element with stable compounds, and the pure metal was not readily obtained until the middle of the 19th century. Because of its light weight (specific gravity 2.70) it is widely used in the shipbuilding and aircraft industries.
Consumer uses include food and beverage packaging, foil, outdoor furniture, and homebuilding materials.
Aluminum was first discovered by Sir Humphry Davy in 1807 and first produced in 1827 by Hans Oersted, who fused potassium with the anhydrous chloride of aluminum in a closed crucible, obtaining the metal in the form of a gray powder. Afterwards Friedrich Wöhler improved this method and succeeded in procuring the metal in a purer form in fused globules and in determining its relative density. In 1854 Henri Sainte-Claire Deville tried the same process, but replaced the potassium by sodium, and the “silver made from clay” of the Paris exhibition of 1855 drew much attention to the question of its economical production. However, no easy way could be found to produce it, and the shiny new metal became more precious than gold. Napoleon is said to have had a set of aluminum cutlery made for his most honored guests. The method now used for its commercial production is the electrolysis of alumina. An iron pot, lined with carbon, is charged with cryolite and heated to about 800şC by the electric current. For the electro
Lysis, a bundle of carbon rods is used as the anode, while the pot itself forms the cathode. The oxygen liberated combines with the carbon of the anode to form carbon dioxide, while the aluminum falls to the bottom of the vessel. More alumina is added and the process continued, the molten metal being drawn off from time to time.
Aluminum is used in the Thermit process for the extraction of high-melting metals from their oxides. Aluminum oxide (see alumina) is used in the manufacture of refractory bricks and as an adsorption filter in chromatography. Aluminum hydroxide is used as a mordant in dyeing and aluminum chloride as a catalyst in organic reactions. Aluminum sulfate is the most widely used chemical in water treatment worldwide, but accidental excess makes drinking water highly toxic, and discharge into rivers kills all fish.A silvery ductile metallic element found primarily in bauxite; SYN. aluminium, Al, atomic number 13.