======Oscillating Clock Reaction======


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**Safety: **{{$demo.safety_description}}\\
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**Alternative titles:** Briggs-Rauscher Reaction, Color-Changing Iodine Reaction
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====Summary====                   
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====Procedure====  
  - Prepare three separate solutions (A, B, and C) as instructed, each containing the required chemicals dissolved in distilled water.  
  - Heat and dissolve starch in water to make a colloidal solution, then add it to solution C.  
  - To perform the demonstration, combine equal volumes of solutions A and B in a beaker.  
  - Immediately add the same volume of solution C to the mixture.  
  - Observe as the solution oscillates between amber and blue-black colors every few seconds.  
  - After several minutes, the oscillations will stop, leaving the solution dark-blue.



====Links==== 
The Briggs-Rauscher Iodine Oscillator - mrhomescientist: 
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Recreating the Briggs-Rauscher oscillating reaction - NileRed: 
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📄 Briggs-Rauscher Reaction - ChemTalk: [[https://chemistrytalk.org/briggs-rauscher-reaction/]]\\


====Variations====
  * Scale the volumes up or down depending on the size of the audience.  
  * Experiment with slightly different starch concentrations to vary the intensity of the blue color.  
  * Record the oscillations with a camera and play back in time-lapse to emphasize the repeating changes.



====Safety Precautions====
  * Wear safety glasses, gloves, and a lab coat when handling all chemicals.  
  * Handle 30% hydrogen peroxide with care; it can burn skin.  
  * Handle sulfuric acid with caution; it is highly corrosive.  
  * Avoid inhaling iodine vapors; they are toxic and corrosive. Perform the reaction in a well-ventilated area or fume hood.  
  * Clean spills and stains with a sodium thiosulfate solution.  
  * Dispose of the final solution properly using sodium thiosulfate neutralization.




====Questions to Consider====
  * Why does the reaction oscillate between colors rather than simply changing once? (Because some reactions proceed quickly while others are slower, causing periodic changes in the concentration of iodine species.)  
  * What role does the starch play in the demonstration? (It forms a visible blue complex with triiodide ions, making the oscillations easier to observe.)  
  * How does the manganese (II) ion affect the reaction? (It acts as a catalyst, producing intermediate species that help drive the oscillations.)  
  * What eventually causes the oscillations to stop? (One or more reactants are consumed, preventing further regeneration of intermediates.)