Experiment 33: Isolating Elemental Iodine

This was an especially fun experiment.  After all, who can resist hand-staining chemicals that give off dense clouds of purple gas?  Iodine is a fun chemical to have around, so I isolated some from sodium iodide.

To do this, I mixed the sodium iodide with just enough water to dissolve it all.  I then dripped sulfuric acid (98%) in until it stopped reacting.  Then, I mixed it well and let it sit for about 10 minutes.  The iodine then precipitated out.  Though I don't entirely understand the chemistry behind this, it relies mainly on the fact that sulfuric acid is both an acid and an oxidizing agent.  Thus, the reaction also works with HCl and H2O2.  NurdRage has good demonstrations of both the H2SO4 and HCl/H2O2 methods of isolating elemental iodine from alkali metal iodides.

I finished the experiment by setting the filtered iodine in a beaker and placing an Erlenmeyer flask filled with ice water on top of it.  The Erlenmeyer flask fit snugly over the beaker, sealing it off.  I placed the assembly on my hot plate and set it to high heat.  The iodine sublimed and then condensed into really neat crystals which I stored in one of the ampules created in Experiment 28: DIY scientific ampoules.  The ampule sealed up very nicely and will store the volatile chemical safely.

It was quite fun adding another element to my collection, and such an interesting, colorful one at that!