RU_KLO
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Iodine missing..... (overoxidized?)
I tried to extract Iodine from iodine-povidone solution.
Everything was going right till the last step - Oxidation of HI by H2O2.
the problem was that, probably added to much H2O2.
This was, because I added some random amount (lets say 10 ml of H2O2 - very old 30%, take it as 10% concentration)
Nothing happen, added 10 more - nothing happen, added 10 more and heated till 50°C- Nothing happened (original solution was aprox 300 ml)
then suddenly, it started bubling hard + heating. luckily it did not overflow and put in a waterbath to cool down.
After 2 - 3 minutes the solution went from coca- cola color to yellow and saw some Iodine flakes, but the bubbling was going strong. So I decided not
to filter it. (tried to filter some with a frited glass filter, but there was an excess of effervecence)
but after 5 more minutes, the iodine dissaperared in a yellow bubbling solution.....
What happened with the Iodine? (does it dissolved?)
The solution was acidic (HCl) + NaCl dissolved inside (because of NaOH + HCl).
the procedure was:
1) Iodinde Povidone solution + NaOH
2) reducing the volume of liquid by boiling - also facilitates removal of povidone
3) making it acidic with HCl
4) oxidizing with H2O2.
Thanks
Go SAFE, because stupidity and bad Luck exist.
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Sir_Gawain
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Iodine is quite volatile, so it probably boiled away. Iodine-povidone only contains about 1% iodine, so it also could have simply dissolved into the
water.
“Alchemy is trying to turn things yellow; chemistry is trying to avoid things turning yellow.” -Tom deP.
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Sulaiman
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Probably in solution as no mention of violet gas,
even a few 10s mg make a visible vapour.
CAUTION : Hobby Chemist, not Professional or even Amateur
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RU_KLO
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yes there was a faint violet gas inside the beaker. A boiling flask with cold water was on top, but no cristals have former. (probably because of
mist/water vapor condensation)
So evaporation is likely to be the main cause.
Could you explain why, as per wiki:
Melting point (I2) 386.85 K (113.7 °C, 236.66 °F)
Boiling point (I2) 457.4 K (184.3 °C, 363.7 °F)
and the solution was monitored to be at 50-60°C
Thanks
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Precipitates
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How much iodine-povidone?
I followed the procedure below, and had no problems - although my iodine is kind of wet (still useable for most purposes though):
Making iodine
Incorrect volumes/concentrations of HCl or H2O2 may mess up your yield.
Excess HCl will catalyse the breakdown of H2O2, especially if the solution is heated - which may have caused the effervescence
observed.
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RU_KLO
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Quote: Originally posted by Precipitates  | How much iodine-povidone?
I followed the procedure below, and had no problems - although my iodine is kind of wet (still useable for most purposes though):
Making iodine
Followed the same procedure, but different quantities.
Iodopovidone 120ml
NaOH 6M aprox 500 ml
reduced by heat to 100ml
HCl 6M til acidic + 20ml more
H2O2 20ml (it was 30% 2 years back, but it degraded - plasic bottle was inflated and every 1-2 months I remove some pressure, so I estimate 10%)
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Precipitates
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| Quote: Originally posted by RU_KLO |
H2O2 20ml (it was 30% 2 years back, but it degraded - plasic bottle was inflated and every 1-2 months I remove some pressure, so I estimate 10%)
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Maybe need more H2O2 then - for your quantity of iodine-povidone, 120 ml of 3% H2O2, or 36 ml of 10%
H2O2.
Titrate to determine the exact concentration of H2O2 you're using if you can.
I'd probably add a large excess - then if the iodine still doesn't precipitate, analyse for other problems.
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Mateo_swe
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Where i live they have in the pharmacies a iodine solution called jodopax that is used to treat animal wounds.
If you ask in the phamacie they also have a concentrated variant of this that is meant to be diluted.
I tried just boil down this concentrated one in a beaker with a roundbottom flask filled with cold water ontop and sure enough, heavy purple vapor
that deposits on the rb flask and can be easily scraped away.
More or less pure iodine.
Maybe there are something similar avaliable where you live?
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