This old post serves as the Video Companion to my Potassium Iodide video, linked at the bottom to make sure you read the post first!
This is another rather long post, but I feel it is warranted because of the importance of the content.
Because of the recent earthquake and tsunami tragedy in Japan, there's been a lot of interest recently in an otherwise ordinary chemical compound called potassium iodide. I'll get to that in a minute, but first a brief summary of the situation.
As you probably are aware, this disaster has caused one of the nuclear power plants on the island to fail and threaten to disperse radioactive materials across the country. In truth, the reactor itself shut down automatically directly after the earthquake, as planned, but the following tsunami overwhelmed the plant and destroyed its cooling systems. Even after the main fission reactions have stopped in a reactor, it remains very hot (both radioactively and thermally) for weeks or months afterward due to secondary decay processes of the products of the primary reaction. So, even though the reactor is technically "off" it still needs to be cooled for quite some time before it is safe to remove and dispose of. Since the cooling systems have failed, the fuel rods in the core threaten to overheat and melt, causing a host of problems. Nearly all of these were planned for in the construction of the plant, but there is still some risk of containment failure and dispersal of radioactive isotopes into the environment. This may have already happened to a small extent, but details are currently scarce or conflicting. It may be some time before all the facts become available. My heart goes out to those in Japan during these troubling times.
So what does this have to do with chemistry? Potassium iodide can be found as anti-radiation pills, taken to protect against exposure to radioactive iodine. Iodine-131 is a radioactive isotope of the regular iodine-127, and is one of the secondary products of the nuclear fission reaction I mentioned above. Iodine is used in the body and concentrated in the thyroid gland. When exposed to significant amounts of radioactive iodine (i.e. from nuclear fallout), it will become concentrated in the thyroid and remains there for much longer than it's half-life of 8 days. There, it can irradiate surrounding tissue and quickly lead to cancer. By taking potassium iodide in "large" amounts (large being only one 130mg tablet a day), you saturate the thyroid gland with normal iodine and this effectively prevents the radioactive variety from being accumulated.
You should remember two important things about this treatment, however. First, it only helps against radioactive iodine. This is only one of many radioactive elements present in fallout, and there isn't much you can do about the others. Second, it only protects the thyroid gland. Radiation damage can still occur in other parts of the body and from those other elements as well. That being said, the potassium iodide defense is still much better than nothing, but it pays to know all the facts.
Some time ago I made a video on my YouTube page on how to make this compound, as I needed it for some lab work. That has gotten a huge surge in views and comments recently, as a direct result of everything I have discussed above. Many suppliers of the tablets are sold out, and people are looking for other ways to obtain it. While this is indeed one way to make this compound, I have to stress the following: I do not recommend anyone ingest potassium iodide made by the method in my video! I do not have the means to guarantee the purity of my reagents or products, and I would never consider eating anything made in the lab. If you did not start with food-grade materials, you will not end up with food-grade product. For those who know a bit about chemistry, you can easily purify iodine by sublimation and recrystallization. You could also purify your potassium iodide from multiple recrystallizations from solution. But, even if you did have exceptionally pure I2 and KOH, however, if you didn't combine them in exactly the right ratios you will have contamination in the finished product. There will also be some KIO3 that you likely won't be able to remove. I can't be sure that there's any way that a home chemist can purify the potassium iodide produced this way into something safely edible.
My video on making this appears below. Enjoy it for the chemistry content, but keep in mind the warnings I pose above.
Periodic Videos also has a great video talking about all of this. They are an excellent science channel, and one of my favorites on YouTube. The Professor is an incredible person! See the video here: http://www.youtube.com/watch?v=-bcrLiATLq0