I think it was Nat Geo.. Not sure exactly.. Where I heard, years ago, that a drop of iodine can be used to disinfect water of say, 1 litre.

But isn't chlorine used to kill all bacteria? I mean I don't completely remember that documentary but I'm pretty sure it was iodine that they used.

Can iodine be used or does my memory fail me?

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    $\begingroup$ "Purify" is the wrong word. You don't purify water by adding more impurities to it. Say "disinfect" instead. Then yes, iodine can be used to that end, as well as chlorine. $\endgroup$ Commented Sep 10, 2017 at 12:02
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    $\begingroup$ As @IvanNeretin states, iodine, as well as chlorine and bromine, are effective disinfectants. See amazon.com/Coghlans-Emergency-Germicidal-Purification-Treatment/…. These halogens, as well as ozone, kill microorganisms though oxidation. [Fluorine is too toxic and corrosive to use for this.] $\endgroup$ Commented Sep 10, 2017 at 22:23

1 Answer 1


Short answer: Both chlorine and iodine in specific concentrations are used for water disinfection.

Iodine has been used to disinfect water for a long time. It is used in concentrations between 2.5 ppm to 7 ppm, but there is some controversy regarding the maximum safe dose of iodine because excess of iodine consumption in humans can lead to various diseases(thyroid disorders being very common). I believe this is the reason we have moved towards more safer options like chlorine for water disinfection.

  • $\begingroup$ What dosage of iodine do you recommend then? You've mentioned it's 2.5ppm to 7 but I regret I'm no pro and don't know into how many drops of iodine it translate into for 1 ltr... Thanks! $\endgroup$
    – Macindows
    Commented Sep 11, 2017 at 11:11

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