[P-man]

What can I do with 99.9% pure iodine?

[pantone159]

It makes a nice element sample.  I have 10 g in a sealed glass bottle, and if I heat it up a bit, I get a pretty purple vapor, which then condenses as crystals on the bottle walls.

You can use I2 to disinfect water.  I have used it this way during backpacking trips, as stream water is not safe without treatment.

It makes a very dark blue complex with starch.

You can make iodide ion with a reducing agent (e.g. vitamin C, thiosulfate, sulfite).  Add lead (II) ion to that to get a nice yellow precipitate.  Or add copper (II) and the iodide will reduce copper and you get a precipitate of copper (I) iodide.

I think there are experiments reacting it with metals, (exothermic!), I haven't done these myself.

Generally, the stuff is kind of a pain because it leaks out of most containers and gets brown stains on everything.

[Kenichi]

I too have been looking into what interesting things one can do with iodine as I've recently learned to extract it from the iodine tincture you can buy at drugstores.  As for the reaction with metals mentioned by Mark. An aqueous solution of sodium, zinc, manganese, iron, nickel or aluiminum (there are probably others) with iodine will give some very violent and visualy pleasing results.  Was messing around in lab the other night and decided to test it out.  You can take powdered aluminum or just aluminum foil and then drop some I2 crystals on top of it.  By simply adding a drop of water or two it will cause the aluminum (or any of the others) and the iodine to burst into purple flames. Note: highly exothermic. Very impressive.  Do this only in a well ventilated area where the iodine fumes won't bother your lungs or eyes.  

[constant thinker]

Also if you try what Kenichi says don't go overboard and use large amounts. Start small. I've learnt that with a variety of things.

I know of some interesting things to do with Iodine, but I'm not at liberty to say them. You could try making Iodic acid (HIO₃). This could be useful for making Iodine salts.

I read about a reaction where after dissolving KI into water you bubble Cl₂ through it. This yields Iodic acid though and KCl I think.

Jdurg wrote an article on Sodium Iodide.
http://www.chemicalforums.com/index.php?op=articles;id=22

[Z-Malti]

I've recently learned to extract it from the iodine tincture you can buy at drugstores. 

Tincture of Iodine is 3% elemental iodine in ethanol. Extracting it will surely produce few amounts of iodine.
As to what you should do with iodine you can make reactions with metals and you could also make nitrogen triiodide with it which is a contact explosive (which is harmless in small amounts.)  [edited] *we cannot post procedures for preparing explosives here * - hmx9123

[limpet chicken]

Passing Cl2 through an iodide solution won't result in iodic acid, it will result in the more reactive halogen (I.E Cl) displacing the less reactive one and yielding elemental iodine.

[pantone159]

Tincture of Iodine is 3% elemental iodine in ethanol.

It also contains KI (or NaI).

[constant thinker]

Passing Cl2 through an iodide solution won't result in iodic acid, it will result in the more reactive halogen (I.E Cl) displacing the less reactive one and yielding elemental iodine.

I read in The Golden Book of Chemistry Expirements. Maybe I miss read it or confused it. I can't find the .pdf on my computer. It dissapeared for some reason. Your probably right then. I know that the Cl will displace the I because of reactivity.

[lemonoman]

What can I do with 99.9% pure iodine?

Sell it   Looks like 50 g goes for about 20 bucks nowadays.  Just depends if your bottle is sealed or not

[P-man]

Thanks for everything. Now I will find some iodine and do some stuff with it!

Pierre.