Radiums Lab - 14-1-2026 at 20:25
Hi guys recently I stumbled upon a video from Apoptis about Hydroiodic acid, in that video he converts the HI back to iodine and uses Sulfuric acid to
turn it into a well crystallised iodine disk, I have never stumbled upon that method so I think it is worth mentioning here.
I have all my iodine in glass ampules so I cannot recreate it.
I think this can be done in test tube scale too so can anyone try it in tiny amounts too?
Here is the video and times stamp is 10:39 :
https://m.youtube.com/watch?v=lRJwfUpjMTE&pp=ygUXQXBvcHR...
He mentions that this method was originally performed by a reddit user so here's his post:
https://www.reddit.com/r/chemistry/comments/k624iy/recrystal...
What do you guys think about this procedure?
This process shows liquid iodine too formed under sulfuric acid in a particular stage, which is fascinating.
It is claimed that this disk is formed due to the sulfuric acid forcing the iodine to form less vapours. Please let me know your thoughts on this.
This might be the best form iodine can be stored in due to the less surface area. This method can be modified to make many shapes too.
I will recreate this if I buy some iodide salt or iodine in the future.
Sulaiman - 14-1-2026 at 20:45
this sounded interesting, maybe a good thing for me to do, but I found this message :
"User-314
•
5y ago
The couple of times I’ve done this I always seem to get residual sulfuric acid crystallized into the iodine. It looks perfect and pristine
originally, but after leaving it in a jar for a few weeks (yes, I know, bad lab practice) it’s started seeping sulfuric acid out of the cracks in
the puck. I have absolutely no idea how to remove the residual sulfuric acid, but it makes me kind of uncomfortable to think that there’s a bunch of
it trapped in the crystal lattice."
https://www.reddit.com/r/chemistry/comments/k624iy/recrystal...
Radiums Lab - 14-1-2026 at 22:32
The user might be facing the issue mostly because he was mixing both of them when they were molten and he might have cooled them immediately after the
mixing step. Iodine is almost 2X denser than sulphuric acid and looking at density difference it's not that possible to get sulphuric acid in the
lattice. Well only experimentation will tell us weather the problem is actually occuring or ...
The layers should be cooled slowly for better crystal growth.
Maybe we can even thest for sulphuric acid being trapped by the iodine by weighing the iodine before making the pancake and after making the
pancake(including the washing step)
If there's a reduction in weight it's explained by the iodine subliming, or wastage due to some being suspended in the sulphuric acid. If there's an
increase in the weight then yes it's trapping the acid.
[Edited on 15-1-2026 by Radiums Lab]
Sulaiman - 15-1-2026 at 00:38
even easier :
water saturated with pure iodine has a pH of 4 or more
so even a little sulphuric acid would be detectable with pH papers etc.
Radiums Lab - 15-1-2026 at 07:19
@Sulaiman If the Sulphuric acid is in the crystals(it didn't seep out) then your test becomes ineffective and the method can only be tested when the
disk will be broken down physically.
Texium - 15-1-2026 at 08:30
I used this method years before that Reddit thread existed, and I’m pretty sure I read about it here before trying it. I experienced the same issue
with entrained sulfuric acid, and I tried to avoid it by keeping the iodine molten for an extended period before allowing it to cool. Nonetheless,
when the puck is broken open, there’s some oily droplets of sulfuric acid within. Makes it kinda useless if you want to use the iodine for anything
that doesn’t already also have sulfuric acid in the reaction.