======Chemical Traffic Light======


<WRAP right box>
**Materials: **{{$demo.materials_description}}\\
**Difficulty: **{{$demo.difficulty_description}}\\
**Safety: **{{$demo.safety_description}}\\
\\
**Categories:** {{$demo.categories}}
\\


**Alternative titles:** Indigo Carmine Redox Indicator
</WRAP>

====Summary====                   
{{$demo.summary}}



====Procedure====  
  - Dissolve about 6 g of glucose in 200 mL of warm distilled water.  
  - Add 40 mL of 1 M sodium hydroxide solution to make an alkaline mixture.  
  - In a separate beaker, dissolve 0.01 g of indigo carmine in distilled water, forming a blue solution.  
  - Combine the alkaline glucose solution with the indigo carmine solution in a larger beaker.  
  - Observe the color change sequence: blue → green → red → yellow as the glucose reduces the indicator.  
  - Shake or swirl the mixture to expose it to air. The solution will re-oxidize, shifting back toward green.  
  - Repeat the shaking and resting process to demonstrate the reversibility of the color changes.



====Links==== 
Chemical Traffic Light - Beautiful chemical Experiment! - Thoisoi2 - Chemical Experiments!: 
{{youtube>-DCkPN_FgOQ?}}\\

Recreating the chemical traffic light reaction - NileRed: 
{{youtube>1ueSa6-UqYo?}}\\

📄 "Chemical Traffic Light" experiment - MEL Science: [[https://melscience.com/AU-en/articles/chemical-traffic-light-experiment/?srsltid=AfmBOor2O7ItMa_ExFTUu2axEoqOcZshStkxUHEa40TCuMR-bGgFDG6Y]]\\


====Variations====
  * Try different sugars (fructose, sucrose) to see how they affect the timing of color changes.  
  * Warm the solution slightly to observe faster reaction rates.  
  * Use different concentrations of sodium hydroxide to see how pH influences the process.



====Safety Precautions====
  * Sodium hydroxide is caustic—wear gloves, safety glasses, and a lab coat.  
  * Indigo carmine and other chemicals used may be toxic—avoid ingestion or skin contact.  
  * Conduct only under professional supervision, not as a casual home experiment.  
  * Dispose of chemical waste properly following institutional safety guidelines.




====Questions to Consider====
  * Why does the solution change color over time? (Glucose reduces indigo carmine stepwise, creating different colored forms of the dye.)  
  * What role does shaking play in the experiment? (Shaking introduces oxygen, which re-oxidizes the dye and reverses the color change.)  
  * How does this experiment illustrate both oxidation and reduction? (Glucose is oxidized while the dye is reduced, and oxygen from air re-oxidizes the dye.)  
  * Why is indigo carmine a good choice for this demonstration? (It has multiple oxidation states with distinct visible colors.)