peroxyl3525
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Potassium Iodide from Potassium Iodate
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I was ordering chemicals online and wasn't being very careful and accidentally ordered KIO3 instead of KI. When the package arrived at my door I was
pretty mad. Does anyone have a procedure to make KI from KIO3? I heard one can decompose potassium chlorate: 2KCLO3 -> 2KCl + 3O2.
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Volanschemia
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I think KIO3 decomposes to KI and O2 at around 500C. Not positive though.
2KIO3 = 2KI + 3O2
[Edited on 20-3-2015 by TheAustralianScientist]
"The chemists are a strange class of mortals, impelled by an almost insane impulse to seek their pleasures amid smoke and
vapor, soot and flame, poisons and poverty; yet among all these evils I seem to live so sweetly that may I die if I were to change places with the
Persian king" - Johann Joachim Becher, 1635 to 1682.
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woelen
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Strong heating of KIO3 produces KI, but you will have a hard time to get it really pure. The reaction is slow and complete decomposition requires
strong heating for a long time. The reaction also has side effects, you will also see formation of iodine vapor and the end product will be alkaline.
It will contain some K2O as well (or possibly KOH, due to absorption of water vapor from air).
I am afraid that the best thing you can do is order some KI.
In aqueous solution things are less bleak. Dissolve some KIO3 in dilute acid and then drip in a solution of sodium sulfite, sodium metabilsulfite or
potassium metabisulfite. First you get a deep brown color, due to formation of iodine, at a certain point you get a lot of iodine and solid iodine
separates. Carefully continue adding Na2SO3 until the liquid becomes colorless (or near colorless). The solution then contains iodide and sulfate
ions, besides the acid. For many experiments requiring iodide, such solutions are useful.
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AJKOER
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Per Atomistry on KI (link: http://potassium.atomistry.com/potassium_iodide.html ), to quote:
"The Potassium iodide, KI, is obtained by neutralizing the carbonate with hydriodic acid, and also by the interaction of potassium hydroxide and
iodine, the iodate simultaneously produced being converted into iodide by heat or by the action of a reducer such as carbon:
6KOH + 3I2 = 5KI + KIO3 + 3H2O.
It is manufactured by the action of iron-filings on iodine in presence of water, the soluble iodide Fe3I8 formed being decomposed by potassium
hydroxide, a process accompanied by precipitation of the oxide Fe3O4 and formation of a solution of potassium iodide. The salt crystallizes on
concentration of the aqueous solution. It can also be prepared from the ashes of seaweed, and from the iodate present in Chile saltpetre."
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peroxyl3525
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Thanks for the replies.
I want just KI so I will try Woelen's suggestion and filter of the iodine and then convert the iodine into potassium iodide.
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morganbw
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Quote: Originally posted by peroxyl3525  | Text
I was ordering chemicals online and wasn't being very careful and accidentally ordered KIO3 instead of KI. When the package arrived at my door I was
pretty mad. Does anyone have a procedure to make KI from KIO3? I heard one can decompose potassium chlorate: 2KCLO3 -> 2KCl + 3O2.
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Please do not toss your KIO3, I am pretty sure you will find a very cool reason to have it in the future
[Edited on 22-3-2015 by morganbw]
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Volanschemia
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Yes, don't.
Here is a couple of pretty nice demos that use Potassium Iodate:
Landolt Clock Reaction
Briggs Rauscher Iodine Oscillator
"The chemists are a strange class of mortals, impelled by an almost insane impulse to seek their pleasures amid smoke and
vapor, soot and flame, poisons and poverty; yet among all these evils I seem to live so sweetly that may I die if I were to change places with the
Persian king" - Johann Joachim Becher, 1635 to 1682.
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peroxyl3525
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Of course I won't. I already have the necessary chemicals for the Clock reaction so I try it out. Sound cool to me. As a side note, is there any
alternative to the Malonic acid in the Briggs Rauscher Iodine Oscillator? I've seen a demo on YouTube and it looks awesome.
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Etaoin Shrdlu
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You want an enolic hydrogen on a water-soluble molecule for replacing malonic acid. It can be done.
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gdflp
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Acetone can be used. This is a more comprehensive paper on one part of the reaction, but the general idea still holds and the reaction is acetone based.
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chloric1
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What about reducing with potassium bisulfite and evaporating to dryness. Then add methanol to the salt mixture and only iodide should be taken up.
Fellow molecular manipulator
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Sir_Gawain
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You could convert to iodine, then dissolve in potassium hydroxide. I agree with morganbw though, keep it.
“Alchemy is trying to turn things yellow; chemistry is trying to avoid things turning yellow.” -Tom deP.
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woelen
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@Sir_Gawain: Dissolving I2 in a solution of KOH gives a mix of iodide and iodate, through intermediate hypoiodite..
fast reaction: I2 + 2 OH(-) ---> I(-) + IO(-) + H2O
slow reaction afterwards: 3IO(-) ---> 2 I(-) + IO3(-)
The net effect is that you get a stoichiometric ratio iodide : iodate = 5 : 1.
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Sulaiman
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As the only posts by peroxyl3525 were in this 2015 thread,
I assume that the problem is solved, or, we've lost an active member.
I doubt that anyone would recommend iodate as a source for iodide
- unless someone happens to have a large unsellable excess stock.
CAUTION : Hobby Chemist, not Professional or even Amateur
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maldi-tof
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I have tried many times to synthetize this product, free from iodates.
The only way was with the iron route, but it is quite hard... the reaction with the potassium carbonate sometimes went crazy and I had to clean
everything because the foam was so intense that it exceed the volume of the beaker.
I also tried to put some KIO3 with charcoal in a muffle oven at 600 °C for 5 days, then dissolve and filter to remove the charcoal, but there were
still iodates in the solution.
I was looking for a maximum of 4 ppm (which is the european pharmacopoeia limit) but it was much higher with this method.
There is another alternative, which is using I2 + KOH, and then add hydracine monohydrate... but it is quite dangerous to use this reagent, even
though it is a very clean reaction, and after heating, the unreacted hydracine is removed.
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