Sciencemadness Discussion Board - Elemental iodine from KI and chlorine?

Elemental iodine from KI and chlorine?

Download - 1-12-2020 at 20:28

I got some potassium iodide in the mail today and was thinking how to convert it to elemental iodine.

I know HI and hydrogen peroxoide is the usual way to do it, but I live in Australia where anything more than 6% H2O2 is hard to get, forcing me to buy expensive little bottles from the chemist.

So I was thinking of using trichloroisocyanuric acid as a chlorine source and just convert my KI in KCl.

Of course there is the issue of interhalogens. I was thinking that maybe I could use a very slight excess of KI and then because they appear to be reversible reactions, I could very carefully heat it with a column on top. So as the interhalogens form and convert back to chlorine and iodine, I can get separation, with chlorine going out the top.

Does this sound feasible to people?

Metallophile - 1-12-2020 at 21:31

I twice attempted to make some I2 by bubbling Cl2 gas into a solution of KI. I got plenty of dark precipitate, but after filtering and drying, I noticed that when crushed, it was almost "juicy" inside with brown liquid. I went on to intentionally chlorinate some of the iodine, and easily made ICl and ICl3. The trichloride decomposed pretty fast on exposure to air, but the monochloride seemed to be much more stable. I don't think it will just convert back like you say.

Download - 1-12-2020 at 21:40

Quote: Originally posted by Metallophile

I twice attempted to make some I2 by bubbling Cl2 gas into a solution of KI. I got plenty of dark precipitate, but after filtering and drying, I noticed that when crushed, it was almost "juicy" inside with brown liquid. I went on to intentionally chlorinate some of the iodine, and easily made ICl and ICl3. The trichloride decomposed pretty fast on exposure to air, but the monochloride seemed to be much more stable. I don't think it will just convert back like you say.

Unfortunate.

I think I'll try with a small amount of bisulfate then.

MidLifeChemist - 2-12-2020 at 07:45

Here is my report on producing Iodine from KI, HCl and 3% H2O2.

http://www.sciencemadness.org/talk/viewthread.php?tid=156295

neddy17 - 2-12-2020 at 15:54

The cleanest and highest yielding way of doing this that I have found is by first dissolving the KI in a slight stoichiometric excess of bleach, diluting a bit with water, and adding H2SO4. Makes chlorine in situ which oxidizes the iodide.

Download - 2-12-2020 at 18:31

Quote: Originally posted by neddy17

The cleanest and highest yielding way of doing this that I have found is by first dissolving the KI in a slight stoichiometric excess of bleach, diluting a bit with water, and adding H2SO4. Makes chlorine in situ which oxidizes the iodide.

Have you tried trichloroisocyanuric acid and HCl in situ?

Fluorite - 19-2-2021 at 13:52

Stupid interhalogens :mad:

I tried making iodine from sodium iodide hcl and tcca but the iodine redissolves!
Sodium iodide and sodium bisulfate reacts when heated and make iodine gas but it's really hard to condense to liquid / solid
And I couldn't find a method to reduce iodate to iodide without heating the solid To high temperatures I'm working with dilute solution right now and boiling to dryness takes a lot of energy

Bedlasky - 19-2-2021 at 17:58

I don't understand. What method do you used? NaI + TCCA + HCl or NaI + NaHSO4? Is second reaction even possible?

Iodine is soluble in excess of iodide forming triiodide anion. So if you used excess of iodide, iodine stayed in solution.

Iodate can be reduce in to iodine by several reducing agents like iodide, metabisulfite, thiosulfate, ferrous sulfate etc, in acidic aqueous solution.