The substance alum, long used as an astringent, is chemically potassium aluminium sulfate. But, the metal component of the compound was unsuspected until the advent of modern chemistry. French chemist Antoine Lavoisier suggested in 1787 that alum contained an unknown metal oxide. In 1808, Sir Humphry Davy failed to isolate the metal, which he first called alumium, then aluminum. The metal was finally isolated by Hans Christian Ørsted in 1825 and by Friedrich Wöhler two years later.
The new metal ultimately gained the conventional -ium suffix for metals. Aluminium, as it was called, binds tightly to oxygen and was therefore very expensive to manufacture. Napoleon III is said to have served his guests on the metal in preference to gold. The capstone of the Washington Monument is 100 ounces of aluminum.
In the late 19th century, Charles Hall in the U.S. and Paul Héroult in France independently developed a much more efficient electrolysis method. Hall called the metal aluminum, and because his company (now Alcoa) dominated production in the United States, the shorter name stuck there.
Mining and Production
Aluminum is the most common element in the Earth's surface, comprising 8% of the crust by weight. Bauxite is the ore of choice, although aluminum could conceivably be extracted from clays and other minerals. World mine production in 2014 was about 234 million tons of ore, the most of any metal except iron, yet down 18% from 2013. The major producing nations were Australia (35%), China, and Brazil.
The Hall process makes aluminum production commercially viable, but it does use a great deal of electricity, 15 kilowatt-hours per kilogram. Therefore, a producing country without abundant reliable power must locate aluminum smelters carefully. World smelter production of aluminum in 2014 was 49 million tonnes. By far the largest aluminum producer was China (47%), followed by Russia and Canada.
Recycling is an important source of aluminum. In the United States, aluminum recovered from beverage cans and other items accounted for about 33% of consumption in 2014.
Properties and Uses
Aluminum is a light weight and relatively strong metal. It is the economically attractive choice of material wherever the greater strength of steel is not required, nor any metal with a special property. Aluminum oxides in air, but immediately forms a protective coat of aluminum oxide that halts the process.
Aluminum is soft, ductile, and malleable. It can be easily formed into sheets and wires or machined into other shapes. A thin coating of aluminum, such as on mirrors, is highly reflective.
Aluminum's electrical conductivity is lower than copper by volume, but greater by weight. Therefore, copper is the better choice in tight spaces, but aluminum is used for electrical transmission lines that must be supported by towers.
Aluminum is used worldwide for vehicles, buildings (such as the Sydney Opera House), and containers. Only steel is used more.