5.5 KiB
| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| History of aluminium | 2/7 | https://en.wikipedia.org/wiki/History_of_aluminium | reference | science, encyclopedia | 2026-05-05T16:15:10.045847+00:00 | kb-cron |
At the start of the Renaissance, the nature of alum remained unknown. Around 1530, Swiss physician Paracelsus recognized alum as separate from vitriole (sulfates) and suggested it was a salt of an earth. In 1595, German doctor and chemist Andreas Libavius demonstrated that alum and green and blue vitriole were formed by the same acid but different earths; for the undiscovered earth that formed alum, he proposed the name "alumina". German chemist Georg Ernst Stahl stated that the unknown base of alum was akin to lime or chalk in 1702; this mistaken view was shared by many scientists for half a century. In 1722, German chemist Friedrich Hoffmann suggested that the base of alum was a distinct earth. In 1728, French chemist Étienne Geoffroy Saint-Hilaire claimed alum was formed by an unknown earth and sulfuric acid; he mistakenly believed burning that earth yielded silica. (Geoffroy's mistake was corrected only in 1785 by German chemist and pharmacist Johann Christian Wiegleb. He determined that earth of alum could not be synthesized from silica and alkalis, contrary to contemporary belief.) French chemist Jean Gello proved the earth in clay and the earth resulting from the reaction of an alkali on alum were identical in 1739. German chemist Johann Heinrich Pott showed the precipitate obtained from pouring an alkali into a solution of alum was different from lime and chalk in 1746. German chemist Andreas Sigismund Marggraf synthesized the earth of alum by boiling clay in sulfuric acid and adding potash in 1754. He realized that adding soda, potash, or an alkali to a solution of the new earth in sulfuric acid yielded alum. He described the earth as alkaline, as he had discovered it dissolved in acids when dried. Marggraf also described salts of this earth: chloride, nitrate and acetate. In 1758, French chemist Pierre Macquer wrote that alumina resembled a metallic earth. In 1760, French chemist Théodore Baron d'Hénouville expressed his confidence that alumina was a metallic earth. In 1767, Swedish chemist Torbern Bergman synthesized alum by boiling alunite in sulfuric acid and adding potash to the solution. He also synthesized alum as a reaction product between sulfates of potassium and earth of alum, demonstrating that alum was a double salt. Swedish German pharmaceutical chemist Carl Wilhelm Scheele demonstrated that both alum and silica originated from clay and alum did not contain silicon in 1776. Writing in 1782, French chemist Antoine Lavoisier considered alumina an oxide of a metal with an affinity for oxygen so strong that no known reducing agents could overcome it. Swedish chemist Jöns Jacob Berzelius suggested the formula AlO3 for alumina in 1815. The correct formula, Al2O3, was established by German chemist Eilhard Mitscherlich in 1821; this helped Berzelius determine the correct atomic weight of the metal, 27.
== Isolation of metal ==
In 1760, Baron de Hénouville unsuccessfully attempted to reduce alumina to its metal. He claimed he had tried every method of reduction known at the time, though his methods were unpublished. It is probable he mixed alum with carbon or some organic substance, with salt or soda for flux, and heated it in a charcoal fire. Austrian chemists Anton Leopold Ruprecht and Matteo Tondi repeated Baron's experiments in 1790, significantly increasing the temperatures. They found small metallic particles they believed were the sought-after metal; but later experiments by other chemists showed these were iron phosphide from impurities in the charcoal and bone ash. German chemist Martin Heinrich Klaproth commented in an aftermath, "if there exists an earth which has been put in conditions where its metallic nature should be disclosed, if it had such, an earth exposed to experiments suitable for reducing it, tested in the hottest fires by all sorts of methods, on a large as well as on a small scale, that earth is certainly alumina, yet no one has yet perceived its metallization." Lavoisier in 1794 and French chemist Louis-Bernard Guyton de Morveau in 1795 melted alumina to a white enamel in a charcoal fire fed by pure oxygen but found no metal. American chemist Robert Hare melted alumina with an oxyhydrogen blowpipe in 1802, also obtaining the enamel, but still found no metal. In 1807, British chemist Humphry Davy successfully electrolyzed alumina with alkaline batteries, but the resulting alloy contained potassium and sodium, and Davy had no means to separate the desired metal from these. He then heated alumina with potassium, forming potassium oxide but was unable to produce the sought-after metal. In 1808, Davy set up a different experiment on electrolysis of alumina, establishing that alumina decomposed in the electric arc but formed metal alloyed with iron; he was unable to separate the two. Finally, he tried yet another electrolysis experiment, seeking to collect the metal on iron, but was again unable to separate the coveted metal from it. Davy suggested the metal be named alumium in 1808 and aluminum in 1812, thus producing the modern name. Other scientists used the spelling aluminium; the former spelling regained usage in the United States in the following decades. American chemist Benjamin Silliman repeated Hare's experiment in 1813 and obtained small granules of the sought-after metal, which almost immediately burned.