Aluminum


Aluminum is the most abundant (8,13%) metallic element in the earth's crust and after oxygen and silicon, the third most abundant of all elements in the crust. Because of its strong affinity to oxygen, it is not found in the elemental state but only in combined forms such as oxides or silicates.

The metal derives its name from alumen, the Latin name for alum. In 1761 L. B. G de Morveau proposed the name alumine for the base in alum, and in 1787 Lavoisier definitely identified it as the oxide of a still undiscovered metal. In 1807 Sir Humphrey Davy proposed the name aluminum for this metal and later agreed to change it to aluminum. Shortly thereafter, the name aluminium was adopted to conform to the "ium" ending of most elements, and this spelling is now in general use throughout the world. Aluminum was also the accepted spelling in the United States until 1925 when the American Chemical Society officially reverted to aluminum.

Hans Christian Oersted is now generally credited with having been the first to prepare metallic aluminum. He accomplished this in 1825 by heating anhydrous aluminum chloride with potassium amalgam and distilling off the mercury. Frederick Wöhler improved the process between 1827 and 1845 by substituting potassium for the amalgam and by developing a better method for dehydrating aluminum. In 1854 Henri Sainte-Claire Deville substituted sodium for the relatively expensive potassium and, by using sodium aluminum chloride instead of aluminum chloride, produced the first commercial quantities of aluminum in a pilot plant near Paris. Several plants using essentially this process were subsequently built in Great Britain, but none survived for long the advent in 1886 of the electrolytic process, which has dominated the industry ever since.

The development of the electrolytic process dates back to Sir Humphrey Davy who in 1807 attempted unsuccessfully to electrolyze a mixture of alumina and potash. Later, in 1854 Robert Wilhelm Von Bunsen and Sainte-Claire Deville independently prepared aluminum by electrolysis of fused sodium aluminum chloride, but this process was not exploited for lack of an economic source of electricity. Gramme's invention of the dynamo (in 1886) changed this and paved the way for the invention of the modern process.

In 1866, Charles Martin Hall of Oberlin (Ohio) and Paul L. T. Héroult of France, both of them 22 years old at the time, discovered and patented almost simultaneously the process in which alumina is dissolved in molten cryolite and decomposed electrolytically. This reduction process, generally known as the Hall-Héroult process, has successfully withstood many attempts to supplant it; it remains the only method to produce aluminum in commercial quantities.