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Author: Subject: Iodine resublimation
Bedlasky
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[*] posted on 8-12-2019 at 08:49
Iodine resublimation


Hi.

I made cca 10g of iodine yesterday from KI, KIO3 and H2SO4. KIO3 was in little excess. I decant supernatant liquid and wash iodine three times with distilled water. After that I tried sublimate it on balcony in hot water bath. But this is very very slow method, because water is cold after a while. Heat it on hot plate isn't possible because on balcony isn't socket. And heat it on hotplate indoor isn't possible too because my girlfriend is very sensitive to iodine.

So, my question is - in all videos on how to make iodine is that iodine must be resublimed because of impurities. What impurities? I tested water from washing and no sign of sulfate or iodide, solution was neutral - so it's really necesary resublime it?

And one more question - how do you store iodine? I have small bottle from brown glass with plastic cap which seems good for this purpose. This bottle I plan place in to the plastic bag.

[Edited on 8-12-2019 by Bedlasky]
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elementcollector1
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[*] posted on 8-12-2019 at 09:11


Where's your sublimation surface? Could do with some additional cooling.

I personally store all my halogens in sealed ampoules immediately after synthesis - it's the one thing they can't seem to find a way to escape from.




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Bedlasky
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[*] posted on 8-12-2019 at 10:24


Sublimation surface is bottom of flask with cold water.
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diddi
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[*] posted on 8-12-2019 at 14:18


as elementcollector says, ampoules are great for display purposes. i do have some I2 stored in double glass GG reagent jars in the freezer also which has proved fine also. Br2 will store in a freezer also i found




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draculic acid69
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[*] posted on 8-12-2019 at 19:09


One of uc235's YouTube videos shows his PFA bottle of frozen bromine.apparently PFA bottles can safely store bromine.also keeping it as a solid sounds like the best way to store it besides ampouling it.also get an extension cord for the balcony
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Sulaiman
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[*] posted on 8-12-2019 at 20:48


You could use a candle as a heat source for your balcony ?
but an extension cord would be more practical.

I've not ampuled iodine, but I've also not found a completely iodine-proof bottle top :D
A little iodine vapour goes a long way ... literally
and being a halogen it can corrode steel and many other metals with ease.

[Edited on 9-12-2019 by Sulaiman]




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Herr Haber
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[*] posted on 9-12-2019 at 04:18


Quote: Originally posted by Bedlasky  
Hi.

And one more question - how do you store iodine?


Away from everything else !
Regular HDPE is enough to store iodine. My last iodine purchase was stored with the invoice rolled around the bottle.
Nothing else got stained but the invoice is unreadable.




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[*] posted on 9-12-2019 at 06:34


Few layers of aluminium foil wrapped around the cap and replaced before corroded throughout (small amounts of escaping halogen react with Al and do not travel further).
IMG_20191209_141901_8_resized.jpg - 41kB

Bottle of Br2 even inside a can surrounded by bags of vermiculite and closed with a lid (a bag below the bottom of bottle is not visible here) - to prevent breaking of glass by some mechanical accident.
IMG_20191209_141918_7_resized.jpg - 34kB

The most safe storage is sealed glass ampule but once opened you can't close it as easily as bottle. And I need to open them more frequently than once.
If you allow halogen vapors to escape, hasta la vista nearby electronics / metal surfaces... I agree with Sulaiman: no completely iodine-proof bottle cap.
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[*] posted on 9-12-2019 at 09:35


i store my sublimated iodine (about 1 gram right now) in a vial, in my freezer. storing everything that evaporates or sublimes easily and can escape containers is best stored at the coldest possible temperature. storing iodine at -20°C lowers its vapor pressure by 2 orders of magnitude versus ambient temperature (20°C)

[Edited on 9-12-2019 by Ubya]





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Dan Vizine
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[*] posted on 17-12-2019 at 19:42


When you ampoule iodine under vacuum you can melt it to a liquid. The vacuum also promotes rapid crystal rearrangement and you can get some really pretty crystals.

Even sublimed reagent grade iodine must be resublimed prior to sample preparation or brown impurities adhere to the glass.

I store both Br and I at room temperature in the glass bottles with special caps that the chemical industry sells them in. Very handy if you can get them. No leakage problems over years.

I2 ampoule.jpg - 700kB close up.jpg - 199kB

[Edited on 12/18/2019 by Dan Vizine]





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[*] posted on 18-12-2019 at 01:52


Very nice sample Dan! Although no one would have expected differently from you of course.
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[*] posted on 18-12-2019 at 08:00


That is a beautiful sample.

Also, I have had little luck keeping iodine in media bottles, it still manages to escape. I would suggest trying one of those glass jars with the pressure sealing glass lids. It still isn’t perfect but its pretty good. All of the bottles stored near my iodine have purple discolored labels from the sealed bottle, even though it had secondary containment.
You also could try a bit of Al foil around the seal, thats how I stop HCl from leaking out of my acid bottle.




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Dan Vizine
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[*] posted on 18-12-2019 at 10:04


Thanks, Tsjerk and Abromination.

In order for a cap to succeed with these materials, it has to do a few different things.

It needs to present an inert face to the material, and this is nearly always made of Teflon. But Teflon has no springiness, which, as Abromination suggested, is desirable in a seal and so the Teflon has to be backed by a chemically-resistant rubber (like Viton). Finally, the cap itself needs to be a robust one (like I think media bottles have?) that can squeeze the layers tightly onto the mouth of the bottle. The Teflon should be as thin as possible so that the closing pressure can deform it. eBay can be a convenient source for some things that you may not have laying around.






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[*] posted on 5-2-2020 at 05:54


I did my iodine experiments over wax paper & stored it in a small wax lined jar.
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