Sciencemadness Discussion Board

iodine (I2)

anonymous201 - 25-10-2011 at 06:58

I have dye of iodine (I2) but I it have only 2 % of concentration , I need it at least to 80 % of purity, are there any way of obtaining Iodine more purity?

The synthesis of Iodine is easy The element may also be prepared in an ultra-pure form through the reaction of potassium iodide with copper(II) sulfate, which gives copper(II) iodide initially. That decomposes spontaneously to copper(I) iodide and iodine:

But i thing is more easy to do it more purity having al 2% of Iodine...

Adas - 25-10-2011 at 07:02

Try to add water, it should percipitate. Or react it with NaOH, and then extract the NaI and put H2O2, you will get nice I2 crystals.

barley81 - 25-10-2011 at 12:06

If you add water to iodine tincture nothing will ppt because with iodide ion (usually put in iodine tincture) iodine forms the triiodide ion, which is soluble.
Brief method for making I<sub>2</sub> crystals from either iodide salts or iodine tincture with iodide salts added:
(2I<sup>-</sup> + 2H<sup>+</sup> + H<sub>2</sub>O<sub>2</sub> ---> I<sub>2</sub>(s) + 2H<sub>2</sub>O)
First acidify the tincture with some dilute acid and then add excess hydrogen peroxide (3%). Iodine will precipitate. Filter, dry, and put in a beaker; add enough conc. sulfuric acid to cover the pellet. Heat this on a hotplate just until the iodine melts into a liquid, then take it off heat (cover with a watch glass). Transfer the pellet to a clean beaker. Put an RBF filled with icewater on top and heat the beaker from the bottom until all of the iodine condenses on the RBF. Let it cool, scrape it off, and bingo! Nice, pure, dry glittery crystals!
I leave calculation of quantity to you as an exercise.

anonymous201 - 25-10-2011 at 15:52

Quote: Originally posted by barley81  
If you add water to iodine tincture nothing will ppt because with iodide ion (usually put in iodine tincture) iodine forms the triiodide ion, which is soluble.
Brief method for making I<sub>2</sub> crystals from either iodide salts or iodine tincture with iodide salts added:
(2I<sup>-</sup> + 2H<sup>+</sup> + H<sub>2</sub>O<sub>2</sub> ---> I<sub>2</sub>(s) + 2H<sub>2</sub>O)
First acidify the tincture with some dilute acid and then add excess hydrogen peroxide (3%). Iodine will precipitate. Filter, dry, and put in a beaker; add enough conc. sulfuric acid to cover the pellet. Heat this on a hotplate just until the iodine melts into a liquid, then take it off heat (cover with a watch glass). Transfer the pellet to a clean beaker. Put an RBF filled with icewater on top and heat the beaker from the bottom until all of the iodine condenses on the RBF. Let it cool, scrape it off, and bingo! Nice, pure, dry glittery crystals!
I leave calculation of quantity to you as an exercise.


I thing that there is one way more easily.By the Sublimation

Iodine produces fumes on gentle heating. It is possible to obtain liquid iodine at atmospheric pressure by controlling the temperature at just above the melting point of iodine.

But quantity of crystals of iodine con i make with 1lt of tincture of iodine?

I thing the best way is buy them in Alibaba.

http://www.alibaba.com/trade/search?SearchText=iodine+crysta...

AndersHoveland - 25-10-2011 at 16:18

I have a question.

It is known that H2O2 can oxidize sodium iodide all the way to sodium iodate. It is also known that sodium iodide acts as a catalyst for the decomposition of hydrogen peroxide. Because of similar reactions with the respective chlorates, I have little doubt that NaOI and NaIO2 will react with H2O2 to liberate oxygen. I also know that H2O2 will reduce NaIO3 in the presence of acid, to form iodine.

My question is this: will H2O2 react with NaIO3 in the absence of any acid? If not, why does NaI catalyse the decomposition of H2O2, when one would think that all the iodide would eventually be oxidized to the inert iodate ions?

simba - 25-10-2011 at 17:58

Quote: Originally posted by barley81  
If you add water to iodine tincture nothing will ppt because with iodide ion (usually put in iodine tincture) iodine forms the triiodide ion, which is soluble.


Funny...because I have been using plain water to extract iodine out iodine tincture successfully.

I2, I- and I3- exist in equilibrium in solution. The water breaks this equilibrium in favor of iodine, which precipitates. That is why plain water also works.