Aluminium Al

Discovery

Alum, a double sulfate containing aluminium, was used in antiquity to fix dyes and stop bleeding. By the late eighteenth century chemists suspected that alumina, the earth in alum, was the oxide of an unknown metal, but it resisted all attempts at reduction.

The Danish physicist Hans Christian Ørsted produced a small, impure sample in 1825 by reacting aluminium chloride with potassium amalgam. Friedrich Wöhler improved the method in 1827 and later described the metal's properties. In the 1850s Henri Sainte-Claire Deville in France developed a sodium-based process that made aluminium available in bars, but it remained so expensive that it was displayed next to crown jewels, and in 1884 an aluminium pyramid was set atop the Washington Monument.

The breakthrough came in 1886, when Charles Martin Hall in the United States and Paul Héroult in France independently invented electrolysis of alumina dissolved in molten cryolite. With Karl Josef Bayer's 1888 process for refining bauxite, the price collapsed and aluminium became a mass-produced metal.

Origin of the name

The name comes from alumen, the Latin word for alum. Humphry Davy first suggested alumium, then aluminum; others preferred aluminium to match elements such as sodium and potassium. IUPAC uses aluminium, while aluminum remains standard in American English. The symbol is Al.

Main uses

• Transport: aircraft, high-speed trains, car bodies and bicycles use aluminium alloys to save weight.
• Packaging: drink cans, foil and food containers.
• Construction: window frames, cladding and roofing.
• Electricity: overhead power lines use aluminium because it conducts well for its weight.
• Household and chemistry: cookware, and aluminium compounds in water treatment and antiperspirants.

Isotopes

Aluminium has only one stable isotope, aluminium-27. The radioactive aluminium-26 has a half-life of about 717,000 years. It is produced by cosmic rays in rocks and in the atmosphere, and geologists pair it with beryllium-10 to date how long sediments have been buried. In the early solar system, aluminium-26 was abundant enough to heat young asteroids, and its decay product magnesium-26 is used to date the oldest meteorite grains.

In everyday life

A thin, invisible oxide film forms instantly on aluminium and protects it from further corrosion, which is why aluminium objects do not rust. Recycling aluminium needs only about 5 percent of the energy required to make new metal from ore, so cans are among the most recycled products.

Aluminium has no known role in the body. It is regarded as low in toxicity at everyday exposures, though people with severe kidney disease must limit it.