Posted on Nov 28, 2011 in Money & finances, Science & nature
Was aluminum really a more expensive metal than gold once upon a time? I read this in a book recently, and am not sure if the author was just taking creative liberty. I mean, aluminum is everywhere now! We even wrap food in it, then throw it away.
We don’t really think about aluminum (or aluminium for any of our British cousins who might be reading this) as being a particularly rare or valuable metal. We buy (and dispose of) aluminum foil by the linear yard, and we go through soda/beer cans by the hundreds every year. In fact, aluminum is the most abundant metal and the third most abundant element in the earth’s crust. Only oxygen and silicon are more common. So how in the world could aluminum ever have been thought to be more valuable than gold?
Aluminum, though amazingly common, is never found in its pure form in nature, as it is far too reactive. The most common ore of aluminum is bauxite, which is a mixture of hydrated aluminum oxide and hydrated iron oxide. As a result, aluminum wasn’t isolated as a metal until 1809, by Sir Humphry Davy, who produced it from alum — the bisulphate salt of aluminum.
Look, I’m sorry, there’s going to be a bit more chemistry. Stick with me.
By 1825, Danish chemist Hans Christian Oersted was able to create an impure sample of aluminum by using heat and a potassium based mixture. The process was improved upon by a German chemist by the name of Friedrich Wöhler who used metallic potassium, but aluminum remained a very rare metal indeed. Then, in 1854, Frenchman Henri Sainte-Claire Deville improved on Wöhler’s idea by substituting sodium for the far more expensive potassium in the process, finally producing enough metal to display at the Paris Exposition of 1854.
Despite this breakthrough, aluminum was still valued at $115 per pound — far more expensive than gold at the time. Napoleon had utensils made out of it and only his most honored guests were given the aluminum forks — the rest had to “settle” for gold. Aluminum was also selected to be the capstone of the Washington Monument in 1884, when at the time the average cost of one ounce of aluminum was equal to a day’s wages for the average worker on the project — and the capstone weighed in at 100 ounces. (You can see a photo of that capstone on the Washington Monument at the top of the page.)
The heyday of aluminum as a precious metal was short-lived, however. By 1886, American Charles Martin Hall and Frenchman Paul L.T. Héroult — interestingly, both were 22 years old at the time — independently discovered a new way to produce aluminum by using electrolysis. They dissolved aluminum oxide in molten cryolite, then passed a strong electric current through the solution. All of the oxygen is removed and deposits of almost entirely pure aluminum are left on the bottom of the bath. Within two years of their discovery, the cost of aluminum had dropped to under $2 per pound, and at the time of this writing (November, 2011) it hovers just under $1 per pound. The Hall-Héroult method, as it became known, is still the preferred process for extracting aluminum today.
Photo: Inscription on the south side of the aluminum tip of the Washington Monument, by the NOAA
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