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Author: Subject: Iodine mishap
chloric1
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[*] posted on 2-4-2005 at 18:05
Iodine mishap


I only post my ignorant mistakes to protect others.

Ok the story begins Thursday when me and my wife where going through a rubbermaid storage bin containing various chems that had been contaminated by a ruptured Chromic Chloride canister. Most of the chemicals though, where salvageable so the exterior of the bottles needed cleaning. One chemical I had was 100 grams of Sodium Iodide that partly oxidized and formed a rock hard cake in the bottle.

Well, iodine being as expensive as it is I could not just toss this stuff. I submerged the whole bottle in 600 ml of near boiling water to get a piss yellow solution. I bioled this down to 300ml and added 200 ml of 40% sulfuruc acid. So now that it had a reasonable concentration of HI, it was now more orange. While still ungodly hot I decided to add my 35% H2O2!:o BIG MISTAKE!!! A HUGE purple cloud instantly erupted spitting iodine/acid solution on my bench. Luckly I escaped the scenario with only two very small stains on my fingers and a little lacrimation effect in my eyes. When the beaker was safe to handle again, I immediately placed in ice water and waited until it was about 5 degrees C. I added the remainder of my peroxide and the entire iodine separated without incident. Lesson to be learned, when isolating halogens or other potentially deadly vapors do so at low temperatures!

Luckily, I was not hurt nor did I suffer excessive property damage, but I realize it could have been MUCH worse. I still have about 50 or 60 grams of iodine I can purify so no loss there. Just remember ,beware but have fun! Keep it safe!

[Edited on 4/3/2005 by chloric1]

[Edited on 4/3/2005 by chloric1]

[Edited on 4/3/2005 by chloric1]




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Saerynide
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[*] posted on 2-4-2005 at 22:03


There was the time when I was extracting I2 from povidone by heating and then condensing the I2 vapors that come off.

I did this by putting the povidone into a small thin-walled jar (with a test tube teflon taped to the opening to condense the I2 in) and then holding it over a candle. I just held it there, watched the I2 come off, and admired the pretty I2 crystals. Then suddenly, it flash-boiled, which resulted in my container exploding, glass shards being blown at me, and having my hand drenched in I2 vapor.

For the remaining half of the day, my hand smelled like I2... Good thing I wasnt cut by any glass shards :o




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darkflame89
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[*] posted on 2-4-2005 at 23:55


I will seize on the topic to reply my experiences with that tough(and vexing) element. I possessed a tincture of iodine from which i tried to extract iodine. Clearly, its a mixture of iodine, alcohol and an iodide salt. My first go at it was to add bleach and vinegar to it. Result: Unsuccessful. I did not see any precipitate even after adding water to it. All I could detect was copius fumes of halogen.(The entire kitchen was filled with it). I could tell whether that fume was iodine or chlorine.(after all, bleach contained a little sodium chloride in it)

My second go, was a slight improvement. I added 1ml of alcohol dropwise to a half a test- tube of water. The alcohol would float on the water. And some of the iodine would suffuse into the water(something to do with equilibrium phase I think). You could see three distinct layers in the water. One was the topmost alcohol layer, which was a deep brown in color. The next layer was iodine which had seeped into water, colouring it brown too. The last layer was pure water, colorless because the iodine had not yet seeped through that far.

I added copper(II) sulphate to the solution dropwise. Ppt would fall thorugh as copper(I) iodide was formed. After some amount of drops, no more ppt was formed, and the layers are missing by now, replaced by uniform brown color throughout the testtube. This (adding of CuSO4) proved that there were iodide in the tincture.

But the tincture/water mixture was still brown, meaning that iodine was still trapped in there. Well, then I was sturck with a sudden idea. Solid iodine reacts with metals with a little water as catalyst. Why should not iodine in alcohol react with metals. I cut out small pieces of aluminium, and threw them into the test tube.

Overnight, the tincture discolored. The iodine was gone, replaced by aluminium iodide. Excess aluminium reacted with excess CuSO4 in solution to form copper metal. The entire test-tube was quite messy.

I repeated the entire experiment, this time instead of aluminium, I used copper metal. Copper metal reacted with the iodine straight to form a ppt. Indeed I was most pleased the next day to find that the brown color of the tincture was gone, lots of fine white ppt collected at the bottom of the test-tube. The copper metal can be removed, the mixture filtered to obtain all the iodine in the alcohol trapped in the form of CuI.

The next prob. is oxidising the CuI to form the iodine back again. I added vinegar(lots of it to the ppt) and added a few crystals of KMnO4 to it. Instantly, MnO2 formed. And everything was spoiled. Evidently, vinegar was just not a strong enough acid.

Bleach won't work either. Bleach by itself only oxidises the ppt to CuO, black ppt too.

Sigh, the prob. of isolating iodine is difficult..(at least here where I live where the acid is not formidable enough). I also want the every bit of iodine that is present, something that is not possible as most oxidisers are water-based. Iodine formed just dissolves into the water, and thus some of it is lost. Sigh :(




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Saerynide
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[*] posted on 3-4-2005 at 00:04


Buy that drain cleaner I told you about, then add 3% H2O2! :D As I have said, I havent tried it in large scale, but it works for test tube amounts :)



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chloric1
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[*] posted on 3-4-2005 at 11:14


Aside from my hazardous mishaps my approach was quite successful and yields where more than acceptable.

So, in light of this, i want to provide the only really good proceedure for procuring iodine in a home lab.

First, you need to obtain sodium iodide or potassium iodide. Purity is not paramount just as long as a high concentration of the iodide could be had without to many interfering anions or organics. I looked at various aquarium and horse products but found the concentration unsatisfactory. Iodides can be had relatively inexpensively and not particularly suspicious or deadly.


Dissolve iodide in warm water and then add sufficient dilute sulfuric acid to generate a bisulfate of the alkali element. You now have a mixture that has HI amongst other things. Cool in ice water to about 5 degrees C. This is important as illistrated above. Finally add sufficient 30%~35% H2O2 to liberate all the iodine and then proceed to sublimation purification.




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chloric1
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[*] posted on 3-4-2005 at 11:18


My weird warped mind finds entertainment is the anamoly I produced here. If you had an inert support I suppose you could make iodine cakes or even iodine cookies in any shape you wanted! YUMMM!:cool::P:P

Iodine cake#1.JPG - 135kB




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[*] posted on 4-4-2005 at 02:09


Well, two things, first i think its quite difficult to get a high concentration of iodide salt(not unless you all try to ship it to me) as the highest concentration is less than 1% in iodized salt. Two, sulfuric acid is not really available in Singapore, not until I have manufactured some for myself, that is. These two are already a big hurdle to overcome when making iodine..



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chloric1
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[*] posted on 4-4-2005 at 09:54


I see said the blindman. No, but really my dilute sulfuric acid was battery acid. I would believe at least one automotive supplier would sell you a quart of this with little hassle. Darkflame, if you are in Singapore, could you just order potassium iodide in China. Everytime I do a Google search I get a zillion pages of buying chemicals from China and India. I think you have to buy in bulk but maybe you could get a bulk quote small enough and take a collection from other chem users and split it accordingly. Any photo hobbyist stores in Singapore? The ones I have delt with in North America are friendly, fair, and have better prices than reagent supply houses. Do some calling around and tell me what you find out.

[Edited on 4/4/2005 by chloric1]

[Edited on 4/4/2005 by chloric1]




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[*] posted on 4-4-2005 at 12:00


I might be old but I have just checked this out and steralised my kitchen and it is still the same as when I was young. If you have iodide or bromide, household bleach will give you iodine or bromine. Make the iodide soluble, excess of sodium and add bleach.
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[*] posted on 4-4-2005 at 16:25


I'm pretty sure that household bleach nowadays is a 5% solution of sodium hypochlorite, so we won't be finding any bromine or iodine in bleach
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[*] posted on 5-4-2005 at 03:29


No, no what mick was saying that the bleach(a oxidiser) can oxidise iodide salts to iodine.

Chloric, I will try around and see.;)




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[*] posted on 5-4-2005 at 06:07


OH! I was reading that after a long day from school, and after studying physics for the longest time :(
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