Iodine

[HopeIDontBlowUp]

A little while ago I decided I'd make some iodine crystals for ammonium triiodide from the iodine mixtures sold at drug stores. At the time I was at home and minus a car, so I rooted around in my medical cabinet and found some old iodine(25 mL). It was 2.5% iodine and 2.5% potassium iodine. I looked around and found a way to get the iodine from it and tried it out.

I grabbed the hot plate, two glass jars and the iodine, went outside and started(temp -8 C or so). I put the iodine in one glass jar and put it on the hot plate, when i saw grey vapour I lit it with a match and it made a big happy flame. When I saw purple vapour I put the other glass jar on top (it's filled with ice water) and let it do its thing for about half an hour. I scraped the gray/silver crystals off and, although there was only a tiny amount it seemed to have worked well.

Given the success of that small amount i went to a drug store and bought 100 mL of iodine which was also 2.5% iodine and 2.5% potassium iodide. I went home and tried again. I did the same as before and the outside conditions were pretty much the same except that it was more like -10 C.

When i lit the grey vapour it burned again. but since it was colder the glass jar broke (just the very top) so i transferred it to another jar. The vapour still burned well but eventually (after about 45 minutes) it stopped burning, but it was still grey. At this point i waited for another 45 minutes and began to think something was amiss. Finally i saw a biht of purple vapour mixed in with the usual grey so i placed the other jar (with water and ice in it) on top. I let it sit for about twenty minutes then checked the bottom of the jar. It was covered in a brown/yellow liquid so i thought that it was probably the grey vapour making it unpure or something so i waited for the vapour to go purple and wiped off the bottom of the jar. Once the vapour was all purple i put the jar back on and it yeilded the same results again.

What did i do wrong, and is there another, easier way of doing this? Also I'm goin to eventually need the potassium iodide for my ammonium triiodide, is there any way of getting that too?

[Zeitgeist]

You're thinking of NI3.NH3.

Nitrogen Triiodide monoammonium complex.

Why do you need the KI ?

I wonder what the flammable vapour is, i doubt it's alcohol because that's the point of the KI to make it water soluble as the I3(-) Triiodide ion.

Clearly the new iodine is different, maybe try a different brand

[Blackhawk]

He dosn't need the KI, but the 'iodine' sold in chemists is usually called tincture of iodine which is infact KI in a solvent, look around for a method of converting it into pure I2 to make your NI3 with.

"Also I'm goin to eventually need the potassium iodide for my ammonium triiodide"
The 'Iodine' you bought from the shop is a soloution of KI IIRC, but you don't use that to make NI3, you need solid pure I2 which you can make from KI.

[Bert]

you need solid pure I2 which you can make from KI.

And the method is posted in the OTHER Iodine thread (http://www.roguesci.org/theforum/showthread.php?t=1002)


Be careful with the NI3. My second batch went off on my desk while drying (I was 15 years old) and my bed was full of broken glass when I came home... If I'd been there, my face would have been full of glass instead. The shock that set it off was my younger brother and his buddy horsing around in the bedroom next to mine and banging on the wall. Make tiny batches, it WILL go off for unbelievably small shocks.

[HopeIDontBlowUp]

The guy I learned this formula from seemed a little... less than trust worthy... Can i send someone the formula I've got for making some Nitrogen Triiodide then tell me if its good or not?

[Zeitgeist]

Just go and find Mega's procedure. It *is* incredibly unstable, far more so than AP or anything like that

I always thought that "iodine" was either I2 in ethanol, or I2 dissolved in Aq. KI which forms the soluble Triiodide ion

[HopeIDontBlowUp]

When I made the NI3 i left the iodine in the ammonia for about two hours and when i came back there was a few bubbles and a little tiny bit of black crystals left. The liquid was still clear and when i dried the very small amoun tof crystals they left purple patches on the filter paper.?????

[T_Pyro]

There are better methods of extracting iodine, if you can't buy it: you could try electrolysis of potassium iodide, with a layer of carbon tetrachloride above the anode to dissolve the iodine liberated. The carbontetrachloride layer could then be separated from the unused electrolyte and evaporated to yield iodine crystals.
NI3 does not need any good reason to go off- if you prepare it corectly, and set it to dry on a layer, you'll hear the regular tell-tale "snaps" and "crackles". Perhaps your iodine (or ammonia) wasn't pure enough, or it went off when you weren't looking.

[vulture]

The easiest and most high yielding method is oxidation of KI (or any other iodine salt for that matter) by H2O2 and H2SO4. No need for concentrated reactants, fairly diluted will do. H3PO4 can also be used, but not HCl for obvious reasons.

[megalomania]

That's a very interesting procedure, vulture. Once you get free iodine, how would you go about purifying it?

[vulture]

Sublimation....

In fact, if you're using 30% H2O2, the mixture will heat up enough to sublime some of the iodine.

Just make sure you use some excess H2O2, because leftover KI will cause some I2 to go back into solution during filtering.

Add the KI + H3PO4, THEN the H2O2. If you add the KI to the H2O2 first (or the other way round) the KI will just catalitically decompose the H2O2.

It's also important to calculate the stoichiometry, because the acid is not a catalyst here, it gets converted to its K-salt and is thus depleted.
The H+ is needed to balance the redox equation.

[chochu3]

At a Agriculture store they sell concentration of up to 7%. The best way i found to make iodine is to add water then add the iodine. add HCl till smoke starts to form. Add a little bit of NaOCl if its starts to turn brown swirl and stop. put in fridge and let it sit for 12 hours. A big chunk of iodine will form.

[chochu3]

If too much NaOcl is added it will over oxidize the iodine forming salt at the bottom and leaving no iodine crystals.

[cyclonite4]

Wouldnt it be possible to get iodine from KI by bubbling chlorine gas through a solution of KI, displacing the iodine and forming KCl.... like so....

2KI + Cl2 --> 2KCl + I2

[Grapes Of Wraith]

I found a great way to make NI3 all you have to do is add the tincture of iodine to corn starch and let it dry in an oven this will evaporate all the alcohol. which will leave you with pure starch iodine this can be added to a solution of ammonia which seems to form NI3 with a byproduct of starch that will form on the bottom of you reaction vessel. I know this works because I made a small batch in a test tube and noticed some small grayish purple crystals on the stopper, I didn't think anything of it but when I tipped the test tube over to observe the rest of the solution the liquid hit the stopper and the stopper blew off shooting ammonia every where. The crystal was the size of a grain of sand. When I looked at the stopper after it exploded the crystal was gone and there was a small discoloration where the crystal was.

[DONMAN]

How many grams per ml of 9-10% I2 solution do you think is necessary to absorb all of the iodine?

[Grapes Of Wraith]

I now know that the crystal on the top of the test tube was I2 not NI3 and the explosion resulted from built up ammonia gas. This is not a good method of production but i would still love to find a way to convert starch iodide into I2 safely and efficiently all that work for one little crystal. The H2O2 method is much better I tried that and it worked great.

[chembio]

Just my 2 cents worth...

If you want to determine whether or not the iodine you have is KI, just add a small quantity iodine sample to a lead compound in its aqueous state. If a yellow, soluble in hot water precipitate is formed, the iodine you have contains KI.

The method above is a quantitative analysis technique to test for the presence of Pb2+ a.k.a. lead ions. It also tels you that your iodine is actually KI :)