“Flag in a Test Tube” experiment
How to wake a three-layered mixture
This colorful and vivid experiment demonstrates the properties of chromium, which in various compounds, depending on the type of oxidation, can have practically all the colors of the rainbow.
Reagents and equipment:
- potassium dichromate;
- amyl alcohol;
- sulfuric acid;
- hydrogen peroxide (10%);
- test tube.
Pour approximately 15-20 ml of potassium dichromate into the test tube, and add 25 ml of amyl alcohol. Observe the layering of the mixture. Then we make our mixture acidic with a small amount of sulfuric acid. Then add 1-2 drops of 10% hydrogen peroxide. We observe the reaction with the release of gas and a change in the color of the solution. The amyl alcohol turns a dark blue color, and the space between the layers turns dark-green, almost black.
When amyl alcohol is added to a potassium dichromate solution, the separation of the mixture takes place. Amyl alcohol is a liquid that dissolves poorly in water and has a lower density, so it will float on the surface of potassium dichromate. After adding hydrogen peroxide, an intense transformation takes place – the liquid between the layers of amyl alcohol and potassium dichromate turns a dark-green (almost black) color. Oxygen is also released. With the interaction of potassium dichromate and hydrogen peroxide in an acidic medium, an unstable compound is formed – chromium(VI) peroxide, which breaks down almost immediately in the aqueous solution and gives the middle layer this dark green color. However, in organic solvents such as amyl alcohol, chromium(VI) peroxide can stabilize and not break down for considerable amount of time. So the upper layer turns blue.
When working with sulfuric acid, wear rubber gloves and protective glasses, as it causes burns on contact with the eyes and skin. Conduct the experiment in a fume hood or a well-ventilated room.
Warning! Substances of this experiment are toxic and highly dangerous for your health. Do not try this at home. Only under professional supervision.