Sciencemadness Discussion Board

iodine clock reaction - recovering the iodide/iodate

jamit - 17-12-2015 at 09:53

Just recently i performed the iodine clock reaction. My problem is that, I want to recover the 50g or so amount of potassium iodide which I used for the clock reaction. I certainly don't want to throw it down the drain as the solution does contain valuable iodine/iodide.

My question is, how can I recover the iodide/iodine since it is mixed with acetic acid, sodium thiosulfate, sodium metabisulfite and potassium iodide and iodine? Any suggestions?

bismuthate - 17-12-2015 at 20:41

The easiest way that I can think of is to mix it with enough HCl and H2O2 to convert all of the iodine into its elemental form. Then mix it with enough MgSO4 to absorb all of the water and finally sublimate the iodine.
I can't give you any amounts without more info on how much of each reagent was used though.

j_sum1 - 17-12-2015 at 22:51

I have not tried it yet but chemplayer on yt gives a nice isolation of iodine using persulfate. Worth a look.

PartVIII - 17-12-2015 at 22:52

You should probably oxidize it back to iodine using H2O2 and HCl, then lightly boil off as much of the solution as possible. Boiling point of iodine is ~183C, so you should be good as long as you don't heat it too much.

Then, once the solution is concentrated, extract it with a nonpolar solvent like hexane. Boil off the hexane, and sublimate for purification.

Volanschemia - 17-12-2015 at 23:22

From experience, Iodine will start sublimating well before 183C, just as water evaporates below 100C, but usually more markedly with Iodine.

j_sum1 - 17-12-2015 at 23:26

Whatever you do, you want a sublimation step to remove the starch.

jamit - 19-12-2015 at 02:16

Quote: Originally posted by bismuthate  
The easiest way that I can think of is to mix it with enough HCl and H2O2 to convert all of the iodine into its elemental form. Then mix it with enough MgSO4 to absorb all of the water and finally sublimate the iodine.
I can't give you any amounts without more info on how much of each reagent was used though.



I'll definitely give the HCl and h2o2 a try to convert everything to iodine... I expect the iodine to drop to the bottom then, i can decant and try to purify it.

PHILOU Zrealone - 19-12-2015 at 13:05

Transform into I2 and extract it with a halogenated solvent...