Aaluminium, Amalgum

ALUMINIUM (ALO2)

Metallic chemical element, chemical symbol Al, atomic number 13.

A lightweight, silvery white metal, it is so reactive chemically that it always occurs in compounds. It is the most abundant metallic element in Earth's crust, chiefly in bauxite (its principal ore), feldspars, micas, clay minerals, and laterite. It also occurs in gemstones, such as topaz, garnet, and chrysoberyl; emery, corundum, ruby, and sapphire are crystalline aluminum oxide. Aluminum was first isolated in 1825, became commercially available in the late 19th century, and is now the most widely used metal after iron. Its surface oxidizes at once to a hard, tough film, deterring further corrosion. Uses include building and construction, corrosion-resistant chemical equipment, auto and aircraft parts, power transmission lines, photoengraving plates, cookware and other consumer goods, and tubes for ointments and pastes. Important compounds include alums; alumina (aluminum oxide), useful as corundum and as a carrier for many catalysts; aluminum chloride, a widely used catalyst for organic syntheses; and aluminum hydroxide, used to waterproof fabrics.

AMALGUM(AMALGAM OF SILVER andTIN)

Alloy of mercury and one or more other metals.

Those of silver, gold, and palladium occur naturally. Those with a very high mercury content are liquid; others are crystalline. Amalgams of silver and tin, with minor amounts of copper and zinc, are used in dentistry to fill teeth. Sodium amalgam is used in manufacturing chlorine and sodium hydroxide by electrolysis of brine. Amalgams are used to recover silver and gold from their ores: The ore is shaken with mercury, the amalgam is separated and heated until the mercury distills off (see distillation), and the precious metal is the residue. Amalgams are also used to silver mirrors and apply other metal coatings.

source: Britannica encyclopedia