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Iodine Chemistry

Updated: Jul 20, 2020

If you've ever scraped your knee or gotten a scratch, your parents or a nurse may have used iodine to disinfect the injury. In my STEAM class this week I decided to teach about Iodine. Iodine turns a starch to have blue-black color. If you put brown iodine on a potato it almost immediately changes the color to a purple tone, but remains brown on oranges, lemons etc. With this, one can determine the presence of starch in a liquid by adding iodine, distinguishing the liquid from glucose, salt solution etc.

Not as many people know that if you add vitamin C into iodine, the brown iodine becomes clear because it turns the iodine into something known as iodide which has a clear color. You can check how much of vitamin C is in your orange juice, lemon juice, or grapefruit juice by adding iodine.

One of the coolest experiments with iodine that I have seen was found from @CoolChemistryGuy. He started the experiment with solid iodine, which I have never seen before. These solid iodine pebbles turned into purple fumes when heated from above. These fumes are toxic, and there was a huge amount of the fumes. I decided to try this experiment at home. I got solid iodine, which stains easily, however no matter how hard i tried, the purple fumes would not show up. I used a hairdryer and... it did not work. I heated the glass filled with the iodine pebbles with a heater and still did not see even tiny amount of the fumes. I wrote to @CoolChemistryGuy and he offered to put the glass with the solid iodine in it into boiling water. The fumes slightly started to appear, but it still was not as big as I would have hoped for. Lastly, he offered to cover the glass and heat the bottom of it with the lighter. And It worked, the purple gas filled the cup. Later on, as the glass cooled out, the gas condensed back into liquid iodine on the top of the foil cover. The glass had simultaneously solid iodine, liquid iodine and gas iodine. Try these iodine experiments at home.

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