First discovered in 1886 by Hans Heinrich Landolt, the iodine clock reaction is one of the best classical chemical kinetics experiments. Here’s what to expect: Two clear solutions are mixed. At first there is no visible reaction, but after a short time, the liquid suddenly turns dark blue.
Usually, this reaction uses a solution of hydrogen peroxide with sulfuric acid, but you can substitute a weaker (and safer) acid that works just as well: acetic acid (distilled white vinegar). The second solution contains potassium iodide, sodium thiosulfate (crystals), and starch (we’re using a starch packing peanut, but you can also use plain old cornstarch). Combine one with the other to get the overall reaction, but note that there are actually two reactions happening simultaneously.
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