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High-grade deposits of bauxite, containing up to 60 percent aluminum oxide, are found most abundantly in Australia, Brazil, and China. Aluminum oxide first has to be extracted from its ore, and then the Hall-Heroult electrolytic process is used to refine the pure metal. Bauxite ore, usually obtained by open-pit (surface) mining, is crushed and washed, and then mixed with caustic soda (sodium hydroxide) at high temperature. The aluminum oxide dissolves while the other components remain as solids and are removed by filtration. Seed crystals are added to precipitate the aluminum oxide. After heating in a kiln to evaporate the water, a white powder of aluminum oxide is left behind.

Electrolytic separation of aluminum metal from its oxide is done in large, steel pots lined with carbon. As in Charles Martin Hall's patented process, molten cryolite acts as the solvent. A carbon rod, inserted into the cryolite from above, is lowered until it comes close to the bottom of the pot. The rod is the positive electrode and the carbon lining of the pot is the negative electrode. Oxygen ions are electrically attracted to the rod, forming carbon dioxide gas, and aluminum ions are attracted to the negative lining, forming molten aluminum metal that sinks to the bottom of the pot. The cryolite is kept hot by resistive heating from the large current flowing between the electrodes, so no external oven is needed. The molten aluminum is siphoned off into a large crucible, from where it is poured into molds to produce solid ingots of metal.

When refined aluminum is removed from a pot, fresh aluminum oxide must be added in order to maintain operation without interruption. Carbon rods gradually wear away due to oxidation and must be replaced periodically. Atypical pot operating with 2,000 amperes of direct current will produce about sixteen kilograms (seven pounds) of aluminum per day. At a large refinery, there may be a hundred or more pots operating in a long line. Refineries usually are situated near hydroelectric power plants because electricity constitutes the largest cost in aluminum production.

Aluminum was unknown to the general public until 1884, when it received widespread national publicity because of its use for the Washington Monument in Washington, D.C. With a height of 550 feet, this was the tallest construction project in the world at the time, and a lightning rod needed to be mounted at the top. The chief engineer decided to use aluminum because it has good electrical conductivity and does not tarnish. At the time, aluminum was considered a semiprecious metal with a cost per ounce equal to that of silver. The Frishmuth Company of Philadelphia was given a contract to make an aluminum pyramid, nine inches high, that would form the cap of the monument. The highly polished pyramid was put on display at Tiffany's jewelry store in New York for people to admire. It was installed in December of 1884, with a copper rod connecting it to the iron scaffold of the elevator shaft leading down to ground.

Hall discovered the electrolytic method for refining aluminum in 1886. Within three years, the small pilot plant in Pittsburgh was producing several thousand pounds per month costing under one dollar per pound. Since that time, aluminum has become the material of choice for a huge number of applications. Aluminum doors, window frames, siding, and gutters are popular in house construction. Aluminum alloys are widely used to manufacture strong beams for large architectural applications. In the aircraft industry, aluminum used for the engine, frame, exterior skin, landing gear, and interior paneling typically makes up 80 percent of a plane's weight. For food packaging, aluminum foil, trays, and billions of beverage cans provide a huge market. In sports equipment, aluminum is used for tennis racquets, skis, baseball bats, canoes, and fishing boats. In automobiles and trucks, aluminum is used for radiators, engine blocks, automatic transmissions, wheels, air conditioners, and body panels, since lighter weight improves the gas mileage. Aluminum wires do not corrode, so they are commonly used for underground electrical cables and for high-voltage cross-country transmission lines. Cooking utensils, appliances for the home, tools, and other consumer goods often are made from aluminum. Except for iron and steel, aluminum has become the most widely used metal in the modern world.

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