They Say the Water in Rio de Janeiro was Bad!

    October 2016:

    I just got back from the Illinois State Fair where the ACS had their tent set up. Frank Salter did many of the demonstrations at the fair and shared this one with me. Apparently back during the Vietnam Conflict, our troops did not always have access to clean, pathogen free water. To remedy this they were given either iodine tablets or a tincture of iodine (this is merely iodine dissolved in some amount of ethyl alcohol). The iodine is a good oxidizing agent and will oxidize, and thus kill the bacteria and viruses. Of course, since iodine is a yellowish brown color and it does not have a particularly pleasant taste, they would want to remove this and they were able to do so with Vitamin C tablets – a good antioxidant.

    Please note:  All chemicals and experiments involve an element of risk, and no experiments should be performed without proper adult supervision.


    • Tincture of iodine
    • A cup of water
    • Vitamin C tablets

    Normally in order to disinfect the water you would only add 5 drops of the iodine to a liter of water, but we want to see a dramatic change so add about 20 drops (1 mL) or so of the iodine to the water. You will see that the water has a very unappealing color and odor to it. Mix the solution. Normally to disinfect the water you would want to allow the iodine to react with the bad elements for about 30 minutes but since we don’t plan to drink the water, we can simply add the vitamin C tablet right away. Stir the solution. After a bit you should notice that the water becomes crystal clear with no bad odor or taste. Additionally now you will get your daily dose of vitamin C!

    The chemical reaction is as follows:

    C6H8O6 + I2 -> C6H6O6 + 2I- + 2H+

    Another ChemShorts article (October 1999) used this same chemistry to determine how much vitamin C is in Tang® drink mix or orange juice.