Thursday, February 18, 2010

Solar (sort of): "7 Mad Science Experiments You Can Do At Home But Probably Shouldn't"

From Neatorama:

4. Making a Deadly Sun

ONE BAD BALL - A white phosphorus 'sun'.

The smoke is phosphorus pentoxide.

Photo: Mike Walker.

HUNK O' BURNING SUN - White phosphorus burning in air glows with a phosphorescent beauty. Photo: Mike Walker.

(1) Suspend the white phosphorus in the center of a lobe filled with pure oxygen. (2) The burning phosphorus rapidly fills the globe with thick white smoke. (3) The chip of phosphorus burns energetically for more than a minute. (4) CLOUDY SUN - It takes about a minute for the phosphorus to burn itself up, leaving only smoke. Photo: Mike Walker.

From urine to firebombs - white phosphorus is among the nastiest of elements.

In 1669 the pompous German alchemist Hennig Brandt accidentally discovered white phosphorus while boiling urine in Hamburg. He became the talk of the town by demonstrating its amazing luminous powers to scientists and dignitaries.

In a cruel irony, 274 years later the discovery he'd hoped would turn lead into gold instead turned his city to ashes when a thousand tons of white-phosphorus incendiary bombs created one of the great firestorms of World War II; 37,000 people died when the sky burned over Hamburg. Yet even today, white phosphorus is still used as a weapon.

I've used red phosphorus to make a batch of kitchen matches. Although both red and white phosphorus contain nothing but the pure element, red is mostly harmless on its own, whereas white is near the top in every category of dangerous. It'll ignite spontaneously and burn vigorously until you deprive it of oxygen. One tenth of a gram inhaled is fatal, and smaller doses over time can make your jaw fall off (seriously - it's called phossy jaw).

The difference is that white phosphorus is a waxy paste consisting of highly strained atoms bound into tetrahedrons. The energy in their chemical bonds is bursting to get out, causing white's high reactivity. The atoms of red phosphorus are linked in relatively stable chains. Same element, very different properties.

Brandt was trying to turn lead into gold, and finding a substance that glows in the dark seemed like a big step in the right direction. Of course, it wasn't, and he died poor after spending two wives' fortunes on boiled urine. (Alchemists were obsessed with urine because it's yellow and they were trying to make gold. Transmuting lead into gold is possible, but it turns out you need a nuclear reactor, not buckets of pee.)

Still, the discovery of white phosphorus was an important one in early chemistry. These days it is used in many ways, including the phosphoric acid in nearly all colas. It's also used in a particularly beautiful classroom demonstration of its extreme flammability and brilliant yellow light. Just hope you never see that light in your neighborhood.

How To Contain a Phosphorus Sun


Half a gram of white phosphorus Pure oxygen gas or liquid oxygen Fire extinguisher
16-inch-glass globe Fume hood Safety glass
Rubber gloves

Suspend about half a gram of white phosphorus in the center of a globe filled with pure oxygen, then touch it with the end of a warm rod to ignite it. The burning phosphorus rapidly fills the globe with thick white smoke, demonstrating one of its military applications: as a smoke screen. The chip of phosphorus burns energetically for more than a minute. The resulting glowing ball is what gives rise to the term "phosphorus sun."

REAL DANGER ALERT: White phosphorus is extremely toxic:
A tenth of a gram can be fatal. It catches fire at a temperature only
slightly above room temperature and is illegal to possess in many states.

Official webpage: Making a Deadly Sun

More, including:

1. Gag with a Spoon: The Melting Spoon Prank

3. Build Your Own Lightbulb

5. Trap Lightning in a Block