The Happy Reaction

I love it when the news media become suddenly and arbitrarily mesmerized by cool chemistry. Slashdot and Wired Science are reporting on the Happy Reaction (aka the Iodine Clock reaction), which converts triiodide to iodide and vice versa in the presence of starch. The equilibria oscillate, so that the solution starts out clear and when triiodide reappears BAM! Blue color. Wired science has a cool video of the process, although I suspect it’s time lapsed.

Next post: results of mechanism calculations on HCN CNH conversion!


  1. It’s a fun one to show kids, especially if you have two people demonstrating.

    You have an accomplice subtly let you know the reaction state with your back to the beaker, facing the youngsters. Then you talk to the kids about some random chemistry detail, and they’ll all holler when the color changes. You act confused, and don’t turn around until your compatriot lets you know it’s cleared again, and then act like the kids are all crazy. They yell and laugh and get all excited, and then you can, for a brief, shining moment, explains some of the details and get every one of them to think science is the shit.

    You can cement that feeling in a few of the kids by immediately blowing something to pieces. These happy few will be destined to be chemists.


  2. Haha sounds almost like a magic act. I’ll definitely try that one on my own kid(s), assuming my wife isn’t too chemistry-phobic to be the accomplice.


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