Iodine Clock Reactions

http://www.youtube.com/watch?v=C5tOEBmBAHg

Above is a video of an iodine clock reaction. It is a simple reaction between water, starch, sodium sulfite, citric acid, and sodium iodate. In the reaction, two clear liquids, one containing water, starch, citric acid and sodium sulfite, and the second containing water and sodium iodate, are mixed together. At first, the created solution stays clear, but after a few seconds the whole solution suddenly completely turns black. The starch and citric acid are in a battle with each other during the reaction. The starch is a catalyst trying to turn the solution black faster, and the citric acid is fighting against the color change keeping it from turning black. Eventually the citric acid gets used up and the starch ultimately wins the battle when the solution turns black. I was highly impressed at this reaction and wanted to figure out a way to recreate it with simpler ingredients. I found that you are able to do it with a few basic ingredients you can pick up at a local pharmacy. You need four items, besides some plastic cups and some water, 1000 mg Vitamin C tablet, tincture of iodine, hydrogen peroxide, and liquid laundry starch. With these few basic items you are able to recreate the iodine clock reaction at home.
For the list of complete directions on how to do this see:
http://www.sciencebob.com/experiments/iodine_clock_reaction.php.

Submitted by: Carrie Bookheimer