In a beaker, you see the liquid changing colors on its own--from red, to yellow, to green, repeat, like a traffic light. But how does this happen? It's actually a chemical reaction involving colorful components, in particular, indigo carmine. When indigo carmine is introduced to oxygen, it is oxidized, and turns green. However, once this mixture is left to stand, the indigo carmine is then reduced by glucose, turning yellow. Then, before it turns back to green, its intermediate stage is red, which gives it its three colors.
If you want to try this yourself, here is the procedure:
If you want to try this yourself, here is the procedure:
- Glucose, 7.5 g
- Sodium Hydroxide, 3.75 g
- Water, Distilled or Deionized, 500 mL
- Graduated Cylinder, 100 mL
- Balance
- Indigo Carmine
- 2 Stirring Rods
- 2 Beakers 600 mL
- Erlenmeyer Flask or Bottle, 1,000 mL
- In a 600-mL beaker add 7.5 g of glucose to 375 mL of water. Stir the mixture until the glucose is dissolved.
- Add a very small amount of indigo carmine to the glucose and water mixture. The solution will turn dark blue.
- In another 600-mL beaker add 3.75 g of sodium hydroxide to 125 mL of water. Stir the mixture until the sodium hydroxide is dissolved.