Sciencemadness Discussion Board

experiments with Iodine Tinctures

sanity gone - 15-6-2004 at 14:18

So I was outside doing some experiments with iodine tinctures and was wondering if anyone could help me with the results.

1. Iodine tincture in sodium hupchlorate (household bleach).
I believe I created some elemental iodine by the reaction of: I` + OCl` --> I2 (I don't know sub or superscripts)

2. Iodine ticutre is added to ammonium hydroixde.
The soln precipitated black and immediatley dissolved to make a clear liquid.
I don't know what happend here, except it seems I created some sort of equilbrium or the solid I created was dissolved in one of the tincture alcohol.
3. Iodine tincture and 5% acetic acid. This one started fuming, and again I am confused. I haven't had time to do this on paper yet, but I am wondering if the gas is hyperiodic acid or just a product of a reaction between the vinegar and alchohol.

hodges - 15-6-2004 at 14:50

For #1 you need to also add an acid (vinegar will do) to get iodine from the KI dissolved in the solution.

Presumably, you know that #2 could form the explosive compound nitrogen triiodide, which can be detonated when dry with the touch of a feather? I wasn't sure; it sounded like you were mixing things at random. In practice, it is probably pretty difficult to get much nitrogen triiodide with such a low concentration of iodine. But if you have solid iodine crystals household ammonia will work - be careful and use no more than a match-head size piece of iodine until you are familiar with the results. And be sure to wear goggles!

sanity gone - 15-6-2004 at 22:01

I knew I could make NI3, but I was doing small amounts with excess ammonia outside. I was trying to get elemental iodine from tincture without using distillation equipment I don't have. Then I also wanted to see if I could make a small amount of NI3 from the tincture itself. So it wasn't all so random... and I always wear my goggles.

darkflame89 - 16-6-2004 at 02:18

Just wondering, could the same be done to povidone iodine?

The_Davster - 16-6-2004 at 06:14

Here is a method of extracting solid iodine from iodine tincture. I have successfully tried it. Vinegar would probally also work in place of sulfuric acid.

As for povidone iodine the same methods will not work. Here is a method of extracting iodine from povidone iodine. I have not tried it because I can get tincture easily. Lastly here is a method by navarone which he claims works better than rhodiums way for extraction of iodine from povidone iodine.

sanity gone - 16-6-2004 at 06:38

Polyvinylpyrrolidone (providone) molecules are incompatible with strong oxidizers... I was wondering if some Proidone mixed with some potassium perchlorate would decompose the providone. This should probally be tired outside becuase it might create carbon monoxide.

darkflame89 - 17-6-2004 at 02:33

After reading the article by Rhodium, I still don't get it; what does acid have to do with the extraction iodine form I2 tincture?

unionised - 17-6-2004 at 11:17

NaOCl + 2KI + H2SO4 ---> I2 + NaCl + K2SO4 + H2O

Without the acid, the reaction does not go properly
(And, most bleach contains excess alkali which reacts with the iodine.)

The_Davster - 17-6-2004 at 11:47

I dont think potassium perchlorate would decompose the povidone. Maybe if it was acidified it would but then there would be most likely side reactions with the iodine after.

darkflame89 - 21-6-2004 at 02:21

Actually, does this equation apply:
2NaOCl+2NaCl+2CH3COOH------------------------>Cl2+2NaCl+2CH3COONa

I tried this today with bleach, vinegar and a dash of table salt. The resulting smell was a strong chlorine smell, but it could have been a cross between vinegar and bleach. It bleached the universal indicator white.

Can anyone reproduce the results? This experiment does not take long to conduct, just mixing..

CoolFool - 9-4-2017 at 11:35

I used vinegar and H2O2.
Is this equation correct?

2KI + 2CH3COOH + 3H2O2 = 2I + 2KCH3COO + 4H2O + O2.

Is it possible to extract the Potassium Acetate from the mixture of Water and Ethanol?

Booze - 16-4-2017 at 06:28

Quote: Originally posted by hodges  
For #1 you need to also add an acid (vinegar will do) to get iodine from the KI dissolved in the solution.

Presumably, you know that #2 could form the explosive compound nitrogen triiodide, which can be detonated when dry with the touch of a feather? I wasn't sure; it sounded like you were mixing things at random. In practice, it is probably pretty difficult to get much nitrogen triiodide with such a low concentration of iodine. But if you have solid iodine crystals household ammonia will work - be careful and use no more than a match-head size piece of iodine until you are familiar with the results. And be sure to wear goggles!

I don't think OP did, because triiodide is insoluble in water.

ave369 - 16-4-2017 at 10:46

Many oxidizers work best at low pH. That's why you need acid.

There's another aspect to this reaction. Potassium iodide increases the solubility of iodine by forming the unstable triiodide anion. When you oxidize the potassium iodide, the solubility of iodine drops dramatically, and it precipitates as well. So the iodine you get from oxidizing the tincture comes from two sources: iodide and free iodine dissolved in it.

Cazangero - 29-7-2017 at 05:45

Lugol's iodine solution contains iodine, potassium iodide and water. Because water is the solvent, this solution relies on the mentioned solubilizing effect of potassium iodide to dissolve the free iodine.

Iodine tincture contains iodine, potassium iodide, water and about 90 % of pure (>= 96 %) ethanol. In this case, ethanol is the main solvent. It contains only about 5 % water, to ease the dissolution of the potassium iodide.

Iodine is not water-soluble, so it needs a lipophilic solvent like oil, ethanol or (in the weakest case) potassium iodide solution.

There are many instructions (even YouTube videos) online that show you how to extract iodine from tincture. These essentially boil down to two steps:

1) Convert the iodine bound in salts to free iodine

When you mix acid with iodine tincture, you convert the potassium iodide to free iodine and the potassium salt of the acid used (e. g. potassium sulfate with sulfuric acid, potassium acetate with acetic acid). This water-soluble salt remains in solution and can be rinsed off. By this method Bernard Courtois first isolated free iodine from iodine salts contained in kelp.

2) Destroy the solvent and precipitate the free iodine

By adding an oxidizer like sodium hypochlorite or hydrogen peroxide, you oxidize the ethanol to acetaldehyde and acetic acid. Since the iodine solvent is transformed to a less lipophilic (or more hydrophilic) species, the dissolved free iodine precipitates.

CRUSTY - 12-8-2017 at 05:45

Quote: Originally posted by Booze  

I don't think OP did, because triiodide is insoluble in water.


Nitrogen triiodide is, however, somewhat soluble in ethanol, IIRC. I've played around with iodine tinctures and ammonia before and I've gotten the black precipitate as well, which upon drying will slowly decompose and leave iodine stains, so I think this is almost certainly triiodide. I didn't have any re-dissolution into the ethanol however, but I suppose it's possible.

Sure, it's nothing like doing a 3 gram triiodide synthesis in the lab (I do this every year for a demonstration I do at a local elementary school), but from what I've seen, tincture addition to aqueous ammonia does produce a very small quantity of triiodide.

rherzal - 17-8-2017 at 07:55

Quote: Originally posted by CoolFool  
I used vinegar and H2O2.
Is this equation correct?

2KI + 2CH3COOH + 3H2O2 = 2I + 2KCH3COO + 4H2O + O2.

Is it possible to extract the Potassium Acetate from the mixture of Water and Ethanol?

This equation is not really correct.
firstly , the iodine atom goes from the -1 oxidation number to 0 oxidation number (oxidation process)
and the oxygen goes from -1 to 0 ; so this is a redox reaction missing the "red"
just eliminate the o2 and the equation will be correct ;)

[Edited on 17-8-2017 by rherzal]