Wednesday, 23 December 2009

Sal Mirabilis!

Mornin' all.
For those who can't sleep for worrying about what's going to turn up in the green gloop, here's a quick note to let you know. After the first day, long clear needles started appearing on the string - up to 2 cm long. As soon as I got the camera out, though, they'd all vanished!

This does happen, sometimes - things crystallise, and then dissolve again. This time, though, it was more mundane - the crystals had got too big and fallen off!

So, a quick decant later, and here they are, growing together in the bottom of the beaker:

The green is just colouring from the solution itself, and don't worry about the brown blob on the right - that's the remains of a paperclip I dropped in for fun. As I might have said, it's good stuff, this!

Now, I know you're dying to know what this is, so here you go:

The crystals have a parallelogram-shaped end that slopes to one side, but are otherwise long thin prisms. Of the possibilities from what went into the gunk (sodium chloride, copper sulphate, and a bit of aluminium) this can only be...



Mirabilite!
(hydrated sodium sulphate, Na2SO4.10H2O)

Nice name for a very nice little crystal. Now, since we've taken some sodium and sulphate ions out, there should be a bit of copper chloride waiting for us after Christmas... that'll be fun! Unfortunately it's doomed to crumble into a white powder once it loses water. But it does make an exceedingly good purgative, as discovered by Glauber in 1645... and hence the name! Miraculous indeed! Any volunteers?
Have a lovely sparkly holiday, and may Santa bring you lots of obscure mineral growths that you've never seen before. If he doesn't, I suggest checking his beard for them. That's where I keep mine.


8 comments:

  1. Dear Dr Rock,

    I am enquiring as to whether you have a vacancy for a lab assistant. I am fully experienced in electrical installation and am excellent at hand sewing.

    I await your reply, sir.

    Your sincerely,

    Igor Igorsson

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  2. Well, now - my very own Igor! Thanks you kindly - what a delightful offer. I'm not entirely clear what the sewing will be useful for, but I suppose some of the needle-like crystals are quite bendy, and would certainly fit through the eye of a needle... although I really wouldn't recommend starting on asbestos fibres.

    In general, though, I always have room for a lab assistant. Are you any good with a blender? Had any practice at cave painting? Please send me your cv by the normal owl-mail procedure (wrapped around an interesting rock, of course), and I'll see what I can do.

    Yours with sparkly bits on,
    Dr. Rock

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  3. I've just found out that mirabilite should dehydrate to thenardite (Na2SO4 rather than Na2SO4.10H2O)... and thenardite is fluorescent! My assistant Kathy is getting some UV lamps, so I think this might be interesting...

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  4. Dear Doc Rock - Where do you conduct all your experiments?

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  5. Well... I must confess that's something I tend to keep quiet about when the wrong people might be listening! Luckily my other half, Dr. Sock, thoroughly approves of these things, so the more hazardous ones I can do at home. I get up to quite a lot in my lab, though - you'll be able to see that once the gallery is ready. With any luck, there will still be some crystals growing in a corner somewhere!

    Of course, I can't possibly let on where the gallery actually is! I only found the place by accident, and I can't afford to be disturbed until then. There are people - believe it or not! - that might want to interfere if they knew about it - so sshhh! It's somewhere in one of the Leeds museums, but that's as much as I'm saying.

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  6. Hi again Doc Rock - Thought I saw you on a bike in the centre of Leeds - was that you?

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