Aluminium

Aluminium was first obtained impure by Hans Christian Oersted in 1825 and prepared more convincingly by Friedrich Wohler in 1827. Its name comes from alum, the astringent double sulfate (Latin alumen) known and used since antiquity as a mordant in dyeing and a styptic in medicine. Despite being the most abundant metal in the Earth's crust, aluminium is so tightly bound in its ores that it long resisted extraction, and until the electrolytic Hall-Heroult process of 1886 it was a rare and costly curiosity. Extracted cheaply ever since, it is now the most widely used metal after iron, prized for being light, strong and corrosion-resistant in everything from cans and foil to window frames and aircraft; it is the most abundant metal in the Earth's crust.

The Hall-Heroult process that finally made aluminium cheap was discovered independently and almost simultaneously in 1886 by Charles Martin Hall in the United States and Paul Heroult in France, each only twenty-two years old and unaware of the other's work; by a further coincidence, both men died in the same year, 1914. Bauxite, the ore from which aluminium is extracted, takes its name from Les Baux-de-Provence in France, where it was first identified in 1821. Aluminium is now the most recycled of common metals in practice, since recycling it uses only about five per cent of the energy required to refine it from ore, a saving that has made can and scrap recycling one of the aluminium industry's central economic facts.

For a few decades aluminium was valued above gold precisely because it was so hard to isolate. Napoleon III is said to have reserved aluminium cutlery for his most honoured guests, and the capstone of the Washington Monument was cast in aluminium in 1884 as a display of a semiprecious metal. The abrupt collapse of its price after 1886 turned it into the commonplace material of foil and aircraft within a generation, a rare case of a metal falling from luxury to ubiquity.

The element also carries a lasting naming dispute: Humphry Davy first proposed alumium, then aluminum, before aluminium was standardised, and American usage retains the older aluminum. Napoleon III's interest was not merely ceremonial: he funded Henri Sainte-Claire Deville's research into aluminium production in the hope of lightening military equipment, and Deville's improved chemical process, unveiled at the 1855 Paris Exposition Universelle, put bars of the metal on public display as a scientific marvel before electrolysis made it cheap. The spelling dispute was formally settled only in 1990, when the International Union of Pure and Applied Chemistry adopted aluminium as the standard international name while recognising aluminum as an acceptable variant, cementing a difference in usage that still divides British and American English today.