How To: Make an Iodine Clock Reaction at Home

Make an Iodine Clock Reaction at Home

In this video, I'll be demonstrating how anyone can make their own iodine clock reaction with simple over-the-counter chemicals.

Household Materials Needed

  • Hydrochloric acid (for cleaning purposes)
  • Hydrogen peroxide (3%)
  • Sodium hydroxide (drain cleaner)
  • Povidone-iodine (antiseptic)
  • Cornstarch
  • Sodium thiosulphate (used as water conditioner for fish bowls, but I got mine from a children's chemistry game)

The Reactions

In the first, slow reaction seen in the video above, triiodide ion is produced:

  • H2O2 + 3 I- + 2 H+ -> I3- + 2 H2O

In the second, fast reaction, triiodide is reconverted to iodide by the thiosulfate:

  • I3- + 2 S2O32- -> 3 I- + S4O62-

The color of the solution after the reaction is a result of the complex formed between iodine and starch that has dark blue color.

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