On this date: aluminum becomes cheap

(AP)

by: David Tristan

Posted: Feb 23, 2023 / 02:33 PM EST

Updated: Feb 23, 2023 / 04:36 PM EST

(WHTM) — It's one of the most common elements on Earth, making up 8.1 percent of the planet's crust, but it didn't even have a name until 1807.

For centuries people made high-quality pottery and fixed dyes in textiles using compounds containing this element, but it wasn't until the 1700s that scientists began to suspect these compounds might contain some unknown type of metal.

In 1807 British chemist Humphry Davy, who had isolated the elements sodium and potassium with an electric current, tried the same thing with the dye fixative containing this mystery metal-and failed. However, his experiment convinced him the element was real and was indeed a metal. The compound was commonly called "alum,", so Davy named the element "alumium". Later he changed it to "aluminum". (Some felt a desperate need to add a syllable and called it aluminium, but here in the United States, we’ve stuck with Davy's original name.) The scientific name for alum became aluminum oxide.

It took almost two decades before anyone succeeded in isolating this strange metal. A Danish physicist and chemist, Hans Christian Ørsted, finally produced an impure sample in 1825 by heating aluminum chloride with potassium, and German chemist Friedrich Wöhler obtained pure aluminum in 1827 by swapping out the potassium for sodium.

With pure samples, scientists were able to study the properties of aluminum. Turns out, the mystery metal was a miracle metal. In its pure form it's soft and malleable, but combines very easily with other elements to form strong, lightweight alloys. It can be easily shaped by almost every metalworking technique, conducts heat and electricity, and is highly resistant to corrosion, because pure aluminum will almost immediately combine with oxygen to form a thin, transparent layer of aluminum oxide. It was obvious aluminum could revolutionize world industry.

All they had to do was figure out how to get it in quantity.

But as Davy, Ørsted, and Wöhler found out, this wasn't easy to do. Because aluminum so easily joins up with other elements, it's almost impossible to find in a pure state. You have to mine material containing aluminum (the most used mineral is called bauxite), then extract it. So in the 19th century, the race was on to find a way to purify aluminum on an industrial scale.

By the 1880s people were producing aluminum in quantity, mostly using variations of Wöhler's process. But they were very small quantities, so small that the capstone placed on the Washington Monument on December 6, 1884, was aluminum, because nothing but the most precious metal on earth would do for the Father of our Country. The going rate for aluminum was $1.10 an ounce; about $33.58 in today's money, and twice the price of silver at the time.

But aluminum would soon cease to be rare and expensive. In 1881, Charles Martin Hall, a student at Oberlin College in Ohio, began experiments in an improvised lab at his family home. Hall had been inspired by a lecture given by Frank Fanning Jewett, the professor of chemistry and mineralogy at the college. In it, Jewett said the person who found a cheap way of refining aluminum would amass a fortune, Hall decided he would be that person.

It took five years and several false starts, but on February 23, 1886, Hall, assisted by his older sister Julia Brainerd Hall, succeeded in producing aluminum by passing an electric current through a solution of aluminum oxide in molten sodium hexafluoroaluminate, commonly known as cryolite. It was simple, it was economical, and it could be scaled up to mass production levels.

At the same time, a French scientist named Paul Héroult independently invented the exact same process. Both Hall and Héroult filed patents in the United States. Fortunately for Hall, he had documents that proved he had produced aluminum before Héroult, and patent No. 400,665 was granted to Hall on April 2, 1889. Héroult was granted a French patent on April 23, 1886, and today their method of smelting aluminum is known as the Hall-Héroult Process.

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Hall found some backers, and they founded the Pittsburgh Reduction Company. (Hall's sister Julia is listed as one of the founders.) By 1888, they were producing almost 50 pounds of aluminum per day. Twenty years later, it was shipping out 88,000 pounds per day. The price of aluminum dropped from $4.86 per pound in 1888 to 78 cents per pound in 1893. A few years later it was down to 25 cents per pound.

The Pittsburgh Reduction Company is still in business. In 1907, the name changed to the Aluminum Company of America. It's now known as Alcoa.

The Aluminum cap on the Washington Monument is still there, still in good shape, and still untarnished by the elements.

To view a video explaining the Hall-Héroult Process click here.

To view a video of actual aluminum refining click here.