Charles Martin Hall


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(1863–1914) American chemist

Hall was born in Thompson, Ohio, and educated at Oberlin College, graduating in 1885. He became interested in the costly process of manufacturing aluminum – until the late 19th century aluminum was a precious metal costing about $5.50 an ounce. Napoleon III would have the majority of his guests served from gold plate; he and the chosen few he wished to impress were served from aluminum plates. Hall was stimulated by a remark of his teacher that anyone who could find a cheap way to make aluminum would win great wealth and fame.

Although the ore itself (bauxite, aluminum oxide) was cheap and plentiful, the metal could only be extracted by electrolysis of the molten ore, and aluminum oxide has a very high melting point. Hall tried various added compounds and, in 1886, found that adding 10–15% of cryolite (sodium aluminum fluoride) reduced the melting point to a little over 1000°C. Hall produced his first sample in the form of buttons, which soon became known as the ‘aluminum crown jewels’. The French chemist Paul Héroult (1863–1914) discovered the process independently at about the same time and the electrolytic method for extracting aluminium is called the Hall-Héroult process. Hall helped to found the Pittsburgh Reduction Company (later the Aluminum Company of America), of which he became vice-president in 1890.

Subjects: Science and Mathematics.

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