February 23 – All That Glitters

Today’s Factismal: The top of the Washington Monument in Washington, DC, is an aluminum pyramid weighing 100 ounces (6.25 lbs).

It may seem strange, but the very apex of the pinnacle of Americana is made of the same stuff that we use for soda cans. The reasons for this are both practical and patriotic, and turn out to reveal a lot about how advances in science can lead to new and unexpected products.

Aluminum is the most abundant metal in the Earth’s crust but reacts so strongly with oxygen that it was never found in a pure state similar to native copper or native iron. Instead, it forms alum salts that are extremely hard to break down chemically. In the 1800s it was so hard to extract aluminum from ores such as bauxite that pure aluminum cost more than pure gold. As a result, when it came time to put a cap on the top of the monument to the greatest American, only the most expensive metal would do.

The Washington Monument, peeking out from the cherry trees

The Washington Monument, peeking out from the cherry trees

But the aluminum cap was for more than just pure decoration. It also served as protection against lightning. When it was constructed, the Washington Monument was the tallest building in the world and stood well above every other building in DC. As another great American, Benjamin Franklin, had shown, tall buildings could be protected against lightning strikes by putting tall, thin rods of copper or another electrically-conductive metal on them. By putting an aluminum cap on the monument, the architects were able to conceal the lightning rod inside the structure itself.

And that’s how matters stood when the Washington Monument was completed in 1884. It was the world’s tallest building and it was capped with the world’s most expensive metal. But within a few years, neither one of these would be true. In 1888, the Eiffel Tower grew to be higher than the monument. And, more importantly, on February 23, 1886, Charles Hall announced his discovery of a way to extract aluminum cheaply and easily from bauxite.

Hall was a chemist who had spent his college career obsessed with the idea of refining aluminum. Like other chemists of the day, he knew that aluminum was ideal for just about any use. Aluminum was lighter and stronger than steel and could be treated to be less likely to rust away. And, if a cheap extraction method could be found, it would be much less expensive due to its abundance. SO Hall persisted in his efforts even after graduation. In a jury-rigged lab in his backyard, Hall worked at finding the best way to extract aluminum. When using catalysts alone didn’t give Hall the results he wanted, he hit upon the idea of running an electrical current through a solution of dissolved aluminum salts; much to his glee, a puddle of pure aluminum quickly formed.

Hall applied for a patent and found a business partner; the two of them then started up what would come to be known as Alcoa. Thanks to his patent, the price of aluminum soon dropped by a factor of 200. Where it once took an entire day’s wages to buy an ounce of aluminum, you could pay for it with three minutes work! Thanks to the radical price drop, aluminum production and use soared form a few pounds a year to 8,000 tons a year by 1900 and to 44,000 tons every year in 2011. Today, more aluminum is made than all other metals (except iron) combined!

And with cheaper aluminum came cheaper aluminum products. Aluminum replaced tin as the metal of choice for cans of food and temporary wrappings. Aluminum was used for car parts, for dirigibles, for airplanes, and for all sorts of decorative goods. Aluminum even features in a roundabout way in fiction; the “Reardon metal” in Atlas Shrugged is based on aluminum. As a result, thanks to one man’s quest for a better process, what was once the world’s most expensive metal is now its most used.

If you’d like to try to create the next aluminum, or just have fun doing science in your hometown, then why not organize a Science Hack Day?

One thought on “February 23 – All That Glitters

  1. Pingback: April 20 – Big Bang – Little facts about science

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