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Reading Selection, Lesson 20

Extracting Aluminum

An elaborate decorative fan made of aluminum

This elaborate ladies' fan with images of the Lincoln assassination is made of aluminum.

Precious Metal
No one knew about aluminum until 1825. That’s when a Danish chemist first extracted pinhead-sized bits of aluminum from a mineral called alumina.
Close up of the aluminum tip on the top of the Washington Monument

In 1884, aluminum was even chosen for a place of honor at the very tip of the Washington Monument, because it was such a rare metal.

But, extracting aluminum from alumina was very difficult, and for most of the 1800s, aluminum was rare and expensive. It was so valuable that kings and queens had fine tea sets and ornamental objects made of aluminum.

Common Metal
Even though aluminum was once considered very rare, it is the most common metal in Earth’s crust, making up 8 percent of Earth’s crust. This aluminum is not found as pure aluminum metal but is combined with other elements in the form of aluminum compounds. Today, aluminum is used for everything from airplane frames to soda cans and baseball bats. It is shiny, strong, and lightweight.
A woman using an aluminum bat.

Aluminum is an excellent material for use in lightweight sports equipment, such as this baseball bat. What other sports equipment is made from aluminum?

It doesn’t rust and can be shaped and cast. It’s even inexpensive enough to use for wrapping leftovers. But aluminum did not become economical until a young inventor working in his backyard lab came up with a low-cost way to extract it from alumina.

Early Start
An eager experimenter, Charles Martin Hall began work on aluminum in 1880. Just 20 years old, he was in his first year at Oberlin College in Ohio.

Backyard Inventor
Working in a woodshed behind his house, Hall set out to find a way to use electric current to get aluminum metal out of alumina, which contains aluminum and oxygen. The hard part was finding the right liquid in which to dissolve the mineral.
Portrait of Charles Martin Hall as a young man.

Charles Martin Hall developed a commercial process for producing aluminum.

Water wouldn’t work. Passing electricity through a water solution of alumina only caused the water to break down into hydrogen and oxygen gas. Instead, Hall dissolved it in another mineral, called cryolite. This was tricky. First he had to melt the cryolite by heating it to more than 1000 ?C. He used carbon electrodes to carry the current, because metal electrodes would have melted.

Illustration of an eletrolytic cell and its parts.

Hall used an electrolytic cell like this one to obtain aluminum metal from alumina.

               



 

Success!
On February 23, 1886, Hall had his first success. After running current through his setup for a few hours, he found several small globs of aluminum inside. He went on to start Alcoa Corporation, still one of the world’s largest producers of aluminum. When Hall died in 1914, much of his fortune went to schools around the world. Oberlin College honors his generosity with this aluminum statue.

Aluminum statue of Charles Martin Hall.

The man and his metal: This statue of Charles Martin Hall is made from aluminum.

 

 

                                                                                                                                                                       
Blobs of Hall's aluminum samples rest on his original notes

Hall’s original samples of aluminum rest on top of his notes about the process he invented.

Question

Conduct a Web search to find how other metals (besides aluminum) are extracted from ore.


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