Precious!

Not all metals oxidize, tarnish, or otherwise form coatings when exposed to air. With the exception of silver, the so-called precious metals - gold, platinum, iridium, palladium, rhodium, ruthenium, rhenium, and osmium - do not react with chemicals in the air, and remain shiny and beautiful. Because of this, they are often used to make jewelry.

And these metals really are precious! Here are some typical prices for one ounce of some precious metals as of July 2011: $40 for silver (not too bad!), $800 for palladium, $1600 for gold, $1800 for platinum, and a whopping $4500 for rhenium!

The funny thing is that one metal used to be precious, but isn't any more, and that's regular old aluminum. We now make disposable cans and food containers out of aluminum (although it's always good to recycle when possible), but at one time, aluminum was more expensive than gold! In fact, in the early 1800's, the French emperor Napoleon had special flatware (forks, spoons, and knives) made out of aluminum, which he used for only his most important dinner guests. Why was aluminum so expensive? Unlike many other metals, aluminum does not occur naturally in pure metallic form. Much of is was found as alum, a mineral from which the aluminum must be separated. In Napoleon's time, this was a very long and difficult process. But in the late 1800's, an American chemist named Charles Martin Hall discovered a process that used electricity to obtain aluminum from alum cheaply and easily. Its price fell from $600 per pound in 1850 to 18 cents per pound in 1914. Hall and some partners formed the Aluminum Company of America (now Alcoa). One other interesting note about Hall - he was very young when he discovered his aluminum process. In fact, he had just graduated from college a few years before!

Fun Facts 11

And finally...

• In the early 1900's, glow-in-the-dark watches were made with paint that contained radium (Ra, #88). Many of the young women who made these watches became very sick because of their exposure to this radioactive element.
• Lutetium (Lu, #71) is probably the most expensive element you've never heard of! It costs more than gold or even platinum!
• Did you know that your pencil doesn't actually contain lead? The stuff you write with is carbon (C, #6) in the form of graphite.
• Humans have been using the metal iron (Fe, #26) for thousands of years. There is a 1500-year old iron pillar in Delhi, India that is still rust-free, probably because it is located in an area with a dry climate.
• The nibs (tips) of very expensive pens may be made with rhodium (Rh, #45) because it does not wear down easily.
• Gas camping lanterns often use a compound of thorium (Th, #90) which glows bright white when heated.
• Rechargeable batteries often contain both nickel and cadmium (Cd, #48). They are called nicad batteries.
• Tin (Sn, #50) slowly disintegrates in temperatures below freezing (32^oF or 0^oC). In the 1700's, organs in unheated churches could be destroyed because their tin-containing pipes would turn brittle and crumble.
• Barium (Ba, #56) X-rays can be used to detect problems in the stomach or digestive tract. Barium sulfate does not let X-rays pass through, so after you drink a barium cocktail, those parts of your body become visible.
• The catalytic converter in your car contains palladium (Pd, #46) which helps to reduce the amount of pollution that comes out of the exhaust pipe.