I have an alcoholic solution of iodine. My goal is to extract the pure iodine without using rare or expensive compounds. How could I do this?
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$\begingroup$ Welcome to chemistry.SE! If you had any questions about the policies of our community, you can visit the help center or take a tour of the website. $\endgroup$– M.A.R.Jan 30, 2015 at 12:28
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$\begingroup$ Is the solvent alcohol, literally? If so, is it 96% ethanol? Does HCl count as expensive for you? It would be nice of you to provide more info. $\endgroup$– M.A.R.Jan 30, 2015 at 13:00
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$\begingroup$ Yes it is 96% alcohol, and I do have HCl $\endgroup$– 666nordless666Jan 30, 2015 at 13:10
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2 Answers
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Alcoholic solution of iodine
What firstly comes to mind is that you meant "iodine tincture".
This question must have been frequently asked, since answers are available out there with different degrees of reliability. You must first follow the safety instructions:
- Do your experiment somewhere that the noxious fumes won't be able to do harm to anyone. It's best to work under a fume hood.
- You're gonna be dealing with strong acids. They're very corrosive when in contact with skin, metals or anything you can imagine (except glass).
- Iodine tends to sublime. If not contained wisely, you'll get irritated skin, along with damages to your eyes (See about iodine hazards here).
In short, what you should do is:
- Pour the tincture in a beaker, or any container. The important thing to note is to have "control" over what's happening in there.
- Add water to the solution. The volume of the water you add should preferably be equal to that of tincture.
- Add $\ce{HCl}$ to the solution, $\approx \pu{5-7 ml}$.
- Add bleach to the solution, preferably equal or more than that amount of $\ce{HCl}$ you added.
- Wait...wait...wait. For a relative amount of time, you should leave the solution for the reactions to happen.
- You've past the hard part! Congratulations! Now, filter the dilute solution with a coffee filter.
Additional tips:
- Iodine crystals sublime, so you shouldn't leave them in open air for long.
- You should at least be wearing appropriate eye and skin protection. If you don't want them, do not do the experiment!
Wikihow has additional tips in case of any failures.
Sources:
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$\begingroup$ ...Or do exactly the same as above, but replace the 5-7ml of 'bleach' (sodium hypochlorite in an aqueous solution with stabilizers and possibly phosphates 'whitening' effect) with 3-5ml 3% H2O2. Both methods produce free chlorine gas, which removes the sodium or potassium from the iodine. $\endgroup$ May 31, 2015 at 6:35
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Your best bet is to evaporate the alcohol from the solution to get Iodine. Iodine boils at $184.3\,^{\circ}{\rm C}$. But the vapor pressure of Iodine causes it to melt anyway. Note: Iodine does actually melt. To resolve this, take a watch glass and put it onto whatever you are using to heat the tincture. This will make the alcohol drip down the center of the watch glass as the iodine deposits/solidifies on the sides. To vent pressure, I recommend you to use a filtering flask and let some of the liquid condense in another flask. You can then re-evaporate. the liquid to get more Iodine. It should be impossible to to get 100% of the Iodine in the solution out, but is is pretty close.
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3$\begingroup$ Since iodine melts, the appropriate description of that temperature is a boiling point, not a sublimation point. There is also a bit of an issue with this, namely the fact that solid and liquid iodine have a significantly large vapour pressure. Simply heating a mixture will cause all the iodine to evaporate along with the solvents. chemistry.stackexchange.com/a/37416/16683 $\endgroup$ May 25, 2016 at 19:57
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$\begingroup$ He was recommending multiple distillations. Using a fractionating system might work or even vacuum distillation possibly (not sure which way the vapour pressures will swing). $\endgroup$– KalleMPFeb 14, 2017 at 20:27