DrMario
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How to dry iodine? (removing microliters of water)
I have accidentally contaminated 100g of iodine with a few microliters of water. How do I remove this water?
I had one idea, but don't want to even try if it will have no effect, or negative effect. My idea would be to put iodine in a 500mL jar and put a
container with silica gel inside it. Close the jar and store it in a cold place. The coldness would be necessary to avoid the iodine from evaporating
too much, but it could also prevent the water from evaporating. I am afraid that iodine itself will permeate the silica gel, maybe even better than
water, render the surface hydrophobic and hence making it not absorb water anymore.
What are your thoughts?
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Dan Vizine
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What makes you think that 100 g of iodine didn't already contain a few microliters of water? Virtually everything does unless extreme precautions are
taken. Take anhydrous solvents for example, strictly speaking, even they aren't anhydrous.
It's merely a question of how much water is still there.
"All Your Children Are Poor Unfortunate Victims of Lies You Believe, a Plague Upon Your Ignorance that Keeps the Youth from the Truth They
Deserve"...F. Zappa
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Metacelsus
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You could try concentrated sulfuric acid as a drying agent.
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Molecular Manipulations
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One microliter = 0.0000010000L. I would do nothing.
But if you meant a lot more than that, I would use a desiccator for a small amount of water (1 gram/100 grams I2) and if more, I'd mix with
a little conc. sulfuric acid, sublimate and recondense.
I just sublimated and recondensed some iodine yesterday, it's really simple.
-The manipulator
We are all here on earth to help others; what on earth the others are here for I don't know. -W. H. Auden
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Hawkguy
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Dude just heat it in a beaker with the top covered by a cool watch glass/ round bottom with ice. The damp Iodine will be deposited on the cool
surface, a lot drier. Just repeat that a few times.
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Mailinmypocket
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Place your iodine under cc sulfuric acid. Heat on a hot plate or flame until the iodine melts under the sulfuric acid and becomes a pool of liquid.
Let the set up cool down so the iodine can harden. Remove the iodine "puck" from the acid and rinse quickly with very cold water. Pat dry with paper
towels. You can crush up the puck of iodine and it is quite dry as is, otherwise you can sublime it onto the bottom of a round bottom flask with ice
water in it, placed on top of the beaker used to heat/sublime the I2.
Note to self: Tare the damned flask.
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DrMario
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Thanks, those are viable methods and I'll consider them.
Any comments on the method I described?
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maleic
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 I think there has nothing else, just go for the experiment !
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woelen
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I would not do anything with it which physically mixes the iodine with other chemicals. E.g. the mixing with H2SO4 probably adds more contamination
than you have now. The I2 indeed does melt and forms a layer under the H2SO4, but are you sure that no H2SO4 is trapped inside the iodine? Maybe the
acid dissolves a little in the iodine, or maybe some small bubbles of acid become trapped in the iodine and do not make it to the surface, before the
iodine solidifies. If you do the trick with H2SO4, then you have to resublime the iodine.
The only thing which you could try is putting the iodine on a small glass dish and put this dish, together with some desiccator in a closed vial for a
day or so, hoping that it absorbs the water. If this does not work, then I would simply accept that there is a small amount of water in the iodine.
Having water-contamination is not as bad as having e.g. contamination with H2SO4.
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morganbw
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Method of purifying and drying crude iodine
US 1857632 A
http://www.google.com/patents/US1857632
This is pretty old but it does vouch for using H2SO4
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j_sum1
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You know, some people store their iodine under water to prevent it subliming away through the lid of their container.
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DrMario
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Well thank you sir! That does confirm the method of using sulfuric acid, to a large extent! I am very satisfied.
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