The aluminum revolution


Aluminum, the third most abundant element in the earth’s crust—and its most plentiful metal—is made from bauxite, a reddish-brown rock discovered in Les Baux, France, in 1821. But it wasn’t until 1886 that chemists finally discovered an economical way to separate pure aluminum from its ore. Two years later, on Thanksgiving Day, a pilot plant in Pittsburgh introduced the first commercial aluminum.

As predicted, the commercialization of this light, lustrous and non-rusting metal has revolutionized the world. Today, aluminum is used to make everything from aircraft to art, buildings, power lines and packaging.

The path to progress
More than 7,000 years ago, Persians made their strongest pottery out of clay containing aluminum oxide. Three millennia later, ancient Egyptians were using other aluminum compounds in medicines, dyes and cosmetics. But because aluminum has a high affinity for oxygen and never occurs in its metallic form in nature, it proved difficult to isolate. In 1808, Sir Humphry Davy gave aluminum its name. In 1825, the Danish chemist Hans Christian Oersted finally produced a sample—albeit very impure—using heat and a potassium-based mixture. Over the next 20 years, Friedrich Wöhler, a German chemist, improved this process by using metallic potassium.


The Paris debut
Henri Sainte-Claire Deville of France substituted potassium with less expensive sodium in 1854 and was able to create enough aluminum for display at the Paris Exposition of 1855. Billed as "silver from clay," aluminum bars were shown alongside France’s crown jewels. The juxtaposition was fitting: rubies, emeralds and sapphires consist mainly of crystalline aluminum oxide.

At that time, pure aluminum was valued at $115 per pound—more expensive than gold. Napoleon III proudly displayed aluminum cutlery at his state banquets, commissioned aluminum equipment for his military and even had an aluminum and gold baby rattle made for his son.

Young scientists
In 1886, Charles Martin Hall of the United States and Paul L.T. Héroult of France—both age 22—independently discovered the way to produce aluminum economically. Hall, under the initial direction of his Oberlin College professor, Frank Fanning Jewett, developed a method for "reducing" aluminum oxide, called alumina, to pure aluminum by electrolysis. In the electrolytic cell, alumina is dissolved in molten cryolite. A strong electric current passes through the solution and removes the oxygen, leaving deposits of nearly pure aluminum on the bottom of the bath. These deposits are siphoned off and cast into pigs. This method is still used today.

 


(Read more.) "Production of Aluminum Metal by Electrochemistry" Landmarks site, from The Challenge through Simultaneous Discoveries

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