Iodine stain damage and iodine storage

Hello, all!

I have a small amount of iodine that I may have mistakenly stored alongside other bottles. While I know iodine tends to stain its surroundings, I assumed it would be fine since its container was unopened and sealed. However, after just a few months, I noticed that all adjacent bottles had become stained, even though they were still wrapped in unopened plastic seals.

I’m trying to determine whether the contents inside those bottles could have been contaminated. Has anyone had a similar experience, and if so, were the contents ultimately unaffected or compromised? I understand there are many professionals here, and I would greatly appreciate any insights you might share.

Please see the picture of the aftermath.

On a separate note, what’s the best way to store iodine, or I would just have to accept that it would stain its surroundings?

Quote: Originally posted by Radiums Lab

What substance is there in above bottle? I stored my Iodine in a glass ampoule. [Edited on 17-8-2025 by Radiums Lab]

just fyi, one example

About 232g iodine stored for over 5 years in various climates.
I saw a dusting of tiny iodine crystals around the neck
the tissue shows what came off.

It is an ex-medicine bottle, not perfect, but the cap has not yet corroded


(photographed just after reading the above posts)

even though the paper labels are covered in tape, some of the ink has been oxidised.

I have tried other bottles/caps, this one is the best survivor so far.

I think that I bought 250g about 8 years ago, only used 18g so far
_____________________________
most iodine deposits slowly evaporate (sublime) away if given ventilation.
I would expect some superficial damage to plastics,
and a very slight porosity to iodine vapour
but unless your reagents are of reference quality I doubt that you would notice.
I would re-bottle. HDPE is great, but certainly not perfect.
(eg both az. sulphuric and az. nitric slowly corrode hdpe)

The shrink-,wrap seems to have absorbed most of the iodine,
I would remove the shrink-wrap and inspect the jar, it looks quite clean.
I would look at the inside of the cap and the top of the jar for indications of iodine.
re-bottling will minimise future doubts.

[Edited on 18-8-2025 by Sulaiman]

Quote: Originally posted by Sulaiman

About 232g iodine stored for over 5 years in various climates. I saw a dusting of tiny iodine crystals around the neck the tissue shows what came off. It is an ex-medicine bottle, not perfect, but the cap has not yet corroded (photographed just after reading the above posts) even though the paper labels are covered in tape, some of the ink has been oxidised. I have tried other bottles/caps, this one is the best survivor so far. I think that I bought 250g about 8 years ago, only used 18g so far _____________________________ most iodine deposits slowly evaporate (sublime) away if given ventilation. I would expect some superficial damage to plastics, and a very slight porosity to iodine vapour but unless your reagents are of reference quality I doubt that you would notice. I would re-bottle. HDPE is great, but certainly not perfect. (eg both az. sulphuric and az. nitric slowly corrode hdpe) The shrink-,wrap seems to have absorbed most of the iodine, I would remove the shrink-wrap and inspect the jar, it looks quite clean. I would look at the inside of the cap and the top of the jar for indications of iodine. re-bottling will minimise future doubts. [Edited on 18-8-2025 by Sulaiman]

Quote: Originally posted by Fery

Cover the I2 package with few layers of Al foil and replace the foil when you observe a corrosion. It works also for Br2, acetyl chloride, SOCl2, anhydrous AlCl3 and so on. All the lab scale I2 produced (or at least packed) in my country was always packed into ground glass joint jars (decades ago, now not anymore and everything "fresh" is from abroad) so there are permanent microleaks through the gap in the ground glass joints and I have to replace the Al foils like once per 3-5 years. I2 is very nasty even in microleaks, if your storage box has metal hinges, they will corrode - it happened in my job when storing I2 disinfectants (solutio iodi spirituosa) - the closest hinges corroded severely and further hinges corroded less.

Quote: Originally posted by j_sum1

I keep a lot of my iodine in ampoules -- various sizes so I can open one most suited to my needs. All of my recovered/recycled iodine is kept this way. I also keep some in the container it was bought in. This is prone to leakage and I know I have lost a proportion of it over the years. I keep this small container in a sealed glass jar with some sodium thiosulfate in the bottom. I find this perfectly adequate for protecting other chems/objects – even if it does not prevent iodine losses.

Quote: Originally posted by Keras

Keep your iodine under concentrated sulphuric acid? It is said to suppress the tendency of iodine to sublime. I have a bottle of HF (yes, yes, that’s dumb) that is wrapped inside a plastic package closed by what I call a swan neck, i.e. the upper part of the package is twisted and crumpled into a sort of big wire, bent and kept tightly closed by a plastic hose clamp. I thought it was impervious, but as the time went by the nearby glass bottle of toluene eroded. The glass is frozen around the point where the two bottles touched.

Quote: Originally posted by chempyre235

I remember someone once reporting on another SM thread that they kept iodine in the freezer. [Edit]: I found some examples. Quote: 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) https://www.sciencemadness.org/whisper/viewthread.php?tid=15... Quote: I store my iodine and H2O2 in our 2nd refrigerator that is in the garage. If I make bromine, I'll probably store that there too, or in the freezer. I like the idea of storing iodine and bromine inside a 2nd container with some base in it, thanks for that idea Woelen. https://www.sciencemadness.org/whisper/viewthread.php?tid=15... Quote: i keep mine in the freezer. no nasty peroxides and no loss. been 2 years at least also keep gallium, DCM and iodine (double bottled) with success https://www.sciencemadness.org/whisper/viewthread.php?tid=79...

Quote: Originally posted by moviez

I understand ampoules are the best storage method but I don’t have high-temp torch in my house (nor am I good at making ampoules). I’ve now moved the iodine bottle to a separate storage container, and it was wrapped with many layers of packaging paper. Unfortunately this wouldn’t prevent iodine from escaping; but it would hopefully prevent it from staining something else. Since iodine stains paper quite easily, I can visually check if iodine vapor has made its way through. You had a brilliant suggestion of using sodium thiosulfate. I will try to clean the stains with it. If the stains are superficial it should come off for the most part. I’ll update later. Quote: Originally posted by j_sum1   I keep a lot of my iodine in ampoules -- various sizes so I can open one most suited to my needs. All of my recovered/recycled iodine is kept this way. I also keep some in the container it was bought in. This is prone to leakage and I know I have lost a proportion of it over the years. I keep this small container in a sealed glass jar with some sodium thiosulfate in the bottom. I find this perfectly adequate for protecting other chems/objects – even if it does not prevent iodine losses.

WOW ! nice cleanup job

Quote: Originally posted by Sulaiman

when I had a lab, sodium thiosulphate solution was one of my 'antidote' chemicals on the shelf immediately behind me when in my usual working location, for halogens but mostly for silver salts.

deionised water

I also have acetone, dilute HCl, dilute NaOH and dilute HNO3 within easy reach, but not in spray bottles. Directly overhead is a large roll of paper towels and another of cleaning cloths.

I still never seem to have a tidy lab, but at least I am covered for a range of minor mishaps.

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moviez - 24-8-2025 at 12:06

Thank you! I actually took a quick video of cleaning the iodine stain of another bottle. It’s quite satisfying to see how it was cleaned!

Quote: Originally posted by Sulaiman

when I had a lab, sodium thiosulphate solution was one of my 'antidote' chemicals on the shelf immediately behind me when in my usual working location, for halogens but mostly for silver salts. I am amazed how nicely you've cleaned it - I usually have to make a new label. (ok, in truth, I often just do nothing and live with ugly labels)

Attachment: My Movie-360p30.mov (1.7MB)
This file has been downloaded 71 times

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moviez - 24-8-2025 at 12:14

That’s very smart to have these spray bottles ready.

I do have a few solutions handy: sodium metabisulfite solution (to clean up chlorate/bromate), sodium thiosulfate (for iodine) and saturated sodium bicarbonate solution (to clean up any acid spill). I just do relatively simple experiments at home but I can imagine a professional lab would prepare far more. It never hurts to be overprepared than being sorry!

Quote: Originally posted by j_sum1

Quote: Originally posted by Sulaiman   when I had a lab, sodium thiosulphate solution was one of my 'antidote' chemicals on the shelf immediately behind me when in my usual working location, for halogens but mostly for silver salts. I keep a row of spray bottles near the entrance to my lab. These get used all the time for clean-ups and spills, and other things too. I have dilute sodium carbonate – tells me where I have been when I am using lead compounds dilute sodium thiosulfate – whenever I am working with oxidisers – especially iodine, nitrates, permanganates, and Cr(VI) dilute hypochlorite solution – only it never seems to work when I need it. The spray nozzle deteriorates too quickly. methylated spirits – 95% ethanol – good for cleaning, rinsing water droplets off glassware, removing sticky labels and marker pen deionised water I also have acetone, dilute HCl, dilute NaOH and dilute HNO3 within easy reach, but not in spray bottles. Directly overhead is a large roll of paper towels and another of cleaning cloths. I still never seem to have a tidy lab, but at least I am covered for a range of minor mishaps.

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