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Friday, March 11, 2005

Safetyland: Mercury Madness

Check out this fine piece of absurdity, complete with a picture of firemen and a HAZMAT team member in bunny suit and face mask "responding" to a high school because somebody apparently spilt some mercury from the chemistry lab. According to CNN, "The building had to be closed twice for decontamination."

Hg_maze.jpg When I was a kid, one of my favourite puzzles was a "mercury maze" like the one at the right. The goal is to get all the drops of mercury into the little cage at the centre of the maze by tilting the maze to make it roll in the right direction, without letting the mercury you've already trapped escape. If somebody's shaken the puzzle, you can consolidate smaller drops into larger ones, but there's too much mercury to get one big blob through the maze all at once.

I also had a couple of bottles of mercury metal. There were lots of cool things you could do with it like dipping a silver coin into it to form a soapy-like amalgam, or dribbling it into a styrofoam cup filled with liquid nitrogen and looking at the shapes you got. Other than the minuscule amount used up in amalgam, mercury is indestructible--you just glob it back together and put it back into the bottle until the next cool idea.

Now prolonged exposure to mercury vapour can make you "mad as a hatter"--in fact the phrase refers to the symptoms hatmakers developed after long-term exposure to mercurous nitrate, which was used in making felt for hats. But like lead and other heavy metals, mercury vapour (the metal itself is not biologically active) is an insidious poison--it builds up in the body, so in the case of low-level exposure, it's the cumulative dose that matters.

Now given the vapour pressure of a few drops of non-finely-dispersed liquid mercury spilt in building the size of a school, don't you think they're over-reacting a bit? But what do I know, I used to play with mercury--I must be mad as a hatter!

If anybody told them there's an entire planet named Mercury visible in the Western sky after sunset this week-end (look for it next to the crescent Moon on the 11th), they'd probably have to evacuate the Earth!

Posted at March 11, 2005 23:37