APO
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Alternative Iodine Isolation
Ok so, I got a fair amount of Iodine recently.
Thirteen 30ml bottles of 2% Tincture of Iodine (USP)
Seven 60ml bottles of 5% Iodides Tincture (Decolorized Iodine)
Two 240ml bottles of 10% Povidone-Iodine (1% equivalent Iodine)
Now I'm thinking I'll add them all together and use an Alkali Metal Hydroxide to form the corresponding Iodide, boil the solution down, filter off
the Polymer formed, and put the solution in my freezer to let the Iodide crystallize out. Then Finally I'll dissolve it in water to make a solution
ready for experimentation.
At 2:11 this video shows the Polymer formed when using Povidone-Iodine: https://www.youtube.com/watch?v=VeQ_BDWm7ls
Now, to make the pure Iodine, here are the usual ways.
Add Hydrochloric Acid to the solution followed by Hydrogen Peroxide: https://www.youtube.com/watch?v=ZFP7fYGrFRI
Add Sulfuric Acid to the solution: https://www.youtube.com/watch?v=2F_kPXbi2D8
Add Sodium Bisulfate to the solution followed by Hydrogen Peroxide: https://www.youtube.com/watch?v=QZLxtbz__XQ
Now, here's one uncommon method:
Acidify the solution with Hydrochloric Acid and then slowly add Sodium Hypochlorite (which first precipitates Iodine and then redissolves it forming
An Iodine Monochloride solution), then add Sodium Bicarbonate to reduce the Iodine Monochloride to Iodine.
Forming the Iodine Monochloride solution: https://www.youtube.com/watch?v=VyZh9v5LnJQ
Reducing the Iodine Monochloride to Iodine: https://www.youtube.com/watch?v=-ttR0kuS_BY
Now here's another:
Add Sodium Hypochlorite to the solution until it turns dark, and then clear again, followed by addition of Hydrochloric Acid to form Iodine. (Could I
use Sodium Bisulfate instead of Hydrochloric Acid?)
Procedure shown at 2:17 here: https://www.youtube.com/watch?v=Yr4GgzVlmmw
Pros, Cons, or Stoichiometry are appreciated, thanks.
[Edited on 1-7-2013 by APO]
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APO
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[UPDATE] 7-3-13
I added all of the Povidone-Iodine, Iodine Tinctures, and Iodide Tinctures to a solution of various Alkali Metal Iodides, now I just need to boil it
down to a eighth of it's volume so I can have the Iodide crystallize out, so I can go on to the next step, converting it to Iodine.
[Edited on 4-7-2013 by APO]
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woelen
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I would add the iodide to some dilute acid (HCl, H2SO4 or HNO3, all are suitable). Use dilute acid (10% or so) and assure that excess acid is used.
Next, add hydrogen peroxide, also a slight excess amount. Iodine is formed, which separates from the liquid as a mud and easily can be separated from
the rest. Use excess hydrogen peroxide, to assure that all iodide is converted to iodine.
Hydrogen peroxide is much better than hypochlorite. As you wrote yourself, hypochlorite redissolves the iodine, forming a mix of iodic acid and
chloroiodates, depending on acid concentration and amount of iodine. These compounds dissolve again and make separation of iodine difficult. So, go
for the hydrogen peroxide.
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chemcam
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I keep telling him that but he won't listen, I even gave him a perfect step-by-step video yet he chooses to reinvent the wheel or multiply the danger
factor by 100.
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APO
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Chemcam, I'm out of Hydrochloric Acid right now, and this thread is for Alternative Iodine Isolation. Can someone give amounts of Sodium Bisulfate
and Hydrogen Peroxide ratios? Those are readily available for me right now. Also I'd like to know the stoichiometry for these reactions as well,
especially for the unconventional methods.
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woelen
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The reaction with bisulfate is as follows:
2NaHSO4 + 2NaI + H2O2 --> 2Na2SO4 + I2 + 2H2O
Just add excess NaHSO4 and excess H2O2. Try on a test tube scale first, such that you don't spoil all of your chemicals in a failed attempt. When
things work fine, then scale up.
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APO
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It just formed a suspension, what should I do? Just count it as failed and wait till I get more Iodides?
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bfesser
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Why on Earth would you combine tinctures of iodine with anything else? Just evaporate off the alcohol.
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weiming1998
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1, Tincture of iodine is usually a mixture of elemental iodine and potassium iodide in alcohol instead of just elemental iodine in alcohol (At least,
the iodine tinctures that I could buy contains this mixture).
2, Iodine is quite volatile, so some of it will evaporate with the alcohol. Given the volume of the alcohol compared to the iodine, a lot of the
iodine would've sublimed away by the time the iodine tincture is evaporated to dryness.
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weiming1998
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Quote: Originally posted by APO  | | It just formed a suspension, what should I do? Just count it as failed and wait till I get more Iodides? |
Try extracting the suspended/dissolved iodine with a small amount of a very volatile, non-polar solvent (e.g ether) and then evaporate off the
solvent.
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APO
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I have toluene, could that work?
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Acidum
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Well, with boiling temp of around 130 degrees celsius, it is faaar from "very volatile".
Just think how would you separate iodine and toluene... 
...and then I disappeared in the mist...
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bfesser
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Thread Pruned
7-7-2013 at 14:19 |
woelen
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If it forms a suspension, then you are halfway. Use a filter to keep the iodine. The filter will turn dark brown, but it does not matter. The iodine
will form a wet slurrie, which needs to be washed with water a few times. You can do that, while it is still in the filter, just rinse it with water
two or three times.
After that, you can remove it from the filter and try to evaporate all of it. Separating it from the water can be hard. If you have concentrated
sulphuric acid, then a very nice way of cleaning the iodine is adding the slurrie to some conc. H2SO4 and heating this stuff. The iodine comes off as
deep purple vapor and can be crystallized on a cold glass surface.
If you really want to obtain iodine in decent quantities, then I strongly suggest you to buy potassium iodide or sodium iodide. The problem with the
tinctures is that they contain alcohol and even worse, they may contain other stuff as well, which together with the iodine gets suspended in the
liquid.
My experience with KI or NaI is that iodine, formed from that and dilute acid (e.g. NaHSO4) and H2O2 forms very nice coarse particles and easily is
separated from the water, even simple coffe filters work perfectly well. Maybe with the tinctures you get a much finer suspension, mixed with all
kinds of goop, which is hard to sepearate.
[Edited on 8-7-13 by woelen]
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APO
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Thanks, woelen.
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amazingchemistry
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I have an slightly off-topic question. both OP and woelen mentioned that adding bleach to tincture of iodine produces iodic acid and chlorine-iodine
compounds. I have an aromatic iodination that requires the use of iodine monochloride (the aromatic ring being already polysubstituted with
electron-withdrawing groups) and I have been looking for a way to do this at home. Do you think using this bleach-tincture mixture as an iodinating
agent would work?
Always remember to check your pride at the door and ask that "stupid" question. Learning comes from having your "stupid" questions answered.
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APO
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Amazingchemistry, could you give a little more detail?
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amazingchemistry
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What I have in mind is to perform the multistep synthesis presented in this paper:
http://pubs.acs.org/doi/pdfplus/10.1021/ed043p213
And also present in Ault's Techniques and Experiments for Organic Chemistry, and, with some modifications, in Schofftall et. al's
Microscale and Miniscale Organic Chemistry Laboratory Experiments. The procedure describes the synthesis of 1-bromo-3-chloro-5-iodobenzene
from benzene (Ault) or Aniline (Schofftall). My goal is to do this using OTC chemicals wherever possible. I'm having a bit of difficulty coming up
with an iodination. The procedure uses iodine monochloride because the iodination is performed as a second-to-last step, after the bromo and chloro
groups have been added. Even without these electron-withdrawing substituents iodine is rather lazy as far as electrophilic aromatic substitution goes,
and so adding it to the substituted ring requires a source of electrophilic iodine. Iodine monochloride is not exactly OTC, and even if I could find a
supplier, it is ridiculously expensive. So I was wondering if the bleach-tincture mixture would work as a source of electrophilic iodine
Always remember to check your pride at the door and ask that "stupid" question. Learning comes from having your "stupid" questions answered.
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woelen
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Iodine monochloride is very easy to make in a pure state. Make a chlorine generator and lead the gas through CaCl2 to make it dry. The Cl2 need not be
pure, it just must be dry. Presence of O2, CO2, HCl, and air is not a problem at all, so simply use cheap swimming pool chlorinator and dilute
hydrochloric acid for the chlorine generator.
The dried chlorine gas must be slowly flowing over solid iodine. You'll see the iodine liquefy immediately due to formation of ICl and if you continue
adding Cl2, you get a bright yellow solid, which is ICl3. Allow formation of ICl and quite some ICl3 and then stop the chlorine generator. Next,
slowly pass dried air (dried with CaCl2) over the ICl+ICl3. The ICl3 quickly decomposes again, giving ICl and Cl2, the latter disperses into the air.
When the yellow color is gone completely you are left with pure ICl in the form of a nearly black liquid, which gives off brown vapor. Using a pipette
you can transfer it to your reaction vessel.
I have done this a few times myself. You need a good fume hood or need to work outside, because of release of chlorine into the air.
[Edited on 10-7-13 by woelen]
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amazingchemistry
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I have seen the ICl synthesis and I think I could perform it but I asked about the bleach-tincture mixture because I find in-situ halogenations
preferable. If this is not possible and I had to synthesize ICl, could I bubble the evolving chlorine gas from the product through through cold water
to trap it? Would some other sort of gas trap work? I don't own a fume hood. I intend to work outside but I want to be extra careful when working with
chlorine (I'm cautious by nature).
Always remember to check your pride at the door and ask that "stupid" question. Learning comes from having your "stupid" questions answered.
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woelen
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I would not do the halogenation directly from the tincture mixture. Tincture contains alcohol, all kinds of other organics and adding of the bleach
introduces a lot of water. ICl reacts with water, giving iodic acid, iodine and hydrochloric acid. In the presence of the organics I expect all kinds
of other reactions as well.
If you want to trap excess Cl2, then use a solution of NaOH. This absorbs chlorine quite well, it is converted to hypochlorite and chloride.
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