"Chemical Traffic Light" experiment
Due to this reactions, liquid will turn green, then red and then yellow
The chemical traffic light is a stunning colorful reaction! The experiment involves changing colors with an indicator – indigo carmine in an alkaline solution of glucose. The alkaline solution of glucose is poured into a solution of indigo carmine, and we observe a gradual change of color: blue – green – red – yellow. We can reverse the reaction simply by shaking the solution. The indigo carmine is oxidized by the oxygen in the air and the colors change in the opposite direction.
Reagents and equipment:
- glucose (6 g);
- indigo carmine (0.01 g);
- 1 M solution of sodium hydroxide (40 ml);
- beakers (3);
- distilled water.
Dissolve approximately 6 ml of glucose in 200 ml of warm distilled water, and add 40 ml of sodium hydroxide solution. In another beaker, dissolve the indigo carmine, creating a blue solution. Then pour the alkaline solution of glucose and the indigo carmine solution into a large beaker and observe the change in color.
Initially, the solution colored by the indigo carmine (blue) is oxidized by the oxygen in the air to a green color – this is the color of its oxidized form. When the green solution is left to stand, the glucose begins to reduce the indigo carmine, first to red, and then to yellow. If you shake the solution or decant it, it mixes with air, and the oxygen once more oxidizes it to green.
When working with sodium hydroxide, wear rubber gloves and protective glasses, as it causes burns if it gets on the skin or in the eyes.
Warning! Substances of this experiment are toxic and highly dangerous for your health. Do not try this at home. Only under professional supervision.