Punk - 31-5-2006 at 14:36
As far as precipitating iodine crystals from tincture goes its no problem, simply add a huge amount of cold h20 a dash of acid and an oxidizer then 20
minutes later a flask full of crystals.
Hypotheticly after useing the iodine to create hydriodic acid and being used as a reducing agent for a certain alcohol then the desired amine is
extracted via acid/base how could one reclaim the iodine in crystaline form?
Adding various amounts of acid, oxidizer and ice cold water does turn the the solution deep red but it just does not want to crystalize no matter what
ratios are used WHY?
[Edited on 31-5-2006 by Punk]
kclo4 - 31-5-2006 at 15:45
well if you are defiantly getting I2 in the solution or what not, you could try to distill or sublimate it out. if you were to distill off the water
with it also, then you would need to bubble chlorine gas into to ppt the I2
Distilling iodine sounds like a bloody mess
Punk - 31-5-2006 at 19:16
The question is WHY the iodine will not precipitate out of the solution.
And a solution to the problem would be how to make it precipitate???
Maybe the chlorine gas is the answer?
chochu3 - 31-5-2006 at 20:44
It dissipates, that's why they used to use the push/pull system.
[Edited on 1-6-2006 by chochu3]
dissopates???
Punk - 31-5-2006 at 23:12
So when useing a condensor with a balloon on top then whare does it go?
It is quite obvious when an oxidizer is added the iodides turn back into iodine but when the ph is brought way down with hcl acid and a large access
of cold h2o is added nothing precipitates.
Ive noticed a solid white crystaline substance that forms in the condensor that fizzes violently in contact with water but that stuff was all returned
to the reaction.
Polverone - 1-6-2006 at 07:06
Is there alcohol or other non-water solvent present in the mixture you are trying to reclaim iodine from? If so, it could be increasing the solubility
to the point that precipitation does not happen.
geezmeister - 1-6-2006 at 08:57
If you neutralize the solution using HCl, you must then add peroxide to the solution for the iodine to precipitate out of it. Add H2O2 until the
solution becomes a dark brown, stir well, let it sit overnight.
A much better approach is to mix H2SO4 with chlorine bleach, about 1 part acid to five parts bleach. Do this in very well ventilated area as it will
produce a good deal of chlorine gas you do not wish to breathe. Add the mix a little at a time to the solution, with much stirring. When you see the
first glimmer of metalic specks, quit adding the acid and bleach and add more water. The iodine will fall out very quickly. You can add too much acid
and foul this extraction up. You don't have to neutralize the solution, actually, but you don't want to make it acidic as that will block the I2
precipitation as well. If you do drop the pH too low, you may be able to raise it by the addition of more of the based reaction fluid, or even more
base, but you usually find a diminished yield when you add too much acid.
It helps a great deal to filter out any solids in the reaction fluid before trying to recover the iodine. You may add warm water to dissolve and
iodides that crystallized out of the solution, but you will also dissolve any NaOH that crystallized as well. Those who use an excess of NaOH in
basing their amine will pay in acid for the overuse of the base.
The HCl/peroxide method is time consuming and low yielding, with maybe a 40% recovery rate of the I2 used initially. The sulfuric acid/ bleach method
will give, when you get the technique down, yields in iodine in the 75-80% range.
A bee of the Hive named Shorty developed a method of adding alchol to the reaction fluid and allowing it time to separate; after the alcohol floated
above the reaction fluid he added acid and oxidizer to the reaction fluid and allowed the alcohol to grab the iodine. He claimed almost complete
recovery, but the folks I know who do this sort of thing never figured out exactly how he did it.
kyro8008 - 1-6-2006 at 13:50
Could the reason why due to the following reaction (which is used with iodide salt to get iodine to dissolve well in water), in your case with the
iodide from any excess hydriodic acid:
I- + I2 --> (I3)-
This will give you the deep red solution I would think.
Punk - 1-6-2006 at 16:06
So hcl and bleach will not let it precipitate? hmmmm
chloric1 - 1-6-2006 at 16:08
According to Merck, iodine has reduced solubility in sulfates and nitrates. I verified this by taking sodium iodide that was yellow and partially
oxidized and caked in its bottle. Instead of wasting it, I dropped the whole thing in 500 ml of hot water. The next day I added a couple hundred
mils of battery acid (sulfuric acid) and the solution became yellow indicating the relatively unstable hydriodic acid was at least in the solution.
I added 30% H2O2 and had an immediate deposit of impure iodine. I sublimed this twice and got a good yeild. I only had an evaporating dish, hot
plate, and beakers. Fun experiment to do. I wish I had more iodide salts.
What is your iodine source? Povidine/iodine?
[Edited on 6/2/2006 by chloric1]
Punk - 2-6-2006 at 13:18
Gallon of 7% for $30
So what is the reaction
Punk - 10-7-2006 at 07:19
What is actually happening when acid and oxidizer is added to a iodine tincture solution?
Is it just creating chlorine gas?
If someone added to much oxidizer that screwed up the precipitation what can be done to reverse it? The solution is still a dark red but its mosly
transparent.
Adding a lye solution does nothing.
woelen - 10-7-2006 at 23:28
Iodine tincture contains some iodide as well. This also is oxidized to iodine, hence the oxidizer. The acid is added, because many oxidizer contain a
lot of oxygen (e.g. KMnO4) and these require acid in order to work well.
Adding too much oxidizer may result in further oxidation of the iodine to iodate (IO3(-) ions). These again go in solution as colorless ions. So, the
amount of oxidizer must be carefully adjusted to the amount of iodide, present in the tincture. Having a too little amount of oxidizer also is not
good. In that case, some iodide remains, which keeps iodine in solution as I3(-) ion.