“Egyptian Night at home” experiment
How to do a classical experiment with starch and iodine
The most mystical experiment of all is “Egyptian Night”. A transparent solution turns dark after a certain time. In this experiment, we’ll show you how to conduct the experiment at home.
Wear protective gloves, a mask and glasses.
Reagents and equipment:
- medical iodine (5% iodine solution in potassium iodide);
- 9% acetic acid;
- 3% hydrogen peroxide;
- 1% starch solution;
- 5% Vitamin C solution (ascorbic acid);
Pour the solutions into the beaker in turn: acetic acid, then medical iodine, ascorbic acid until the mixture becomes colorless, then starch and hydrogen peroxide. Observe the solution in the beaker turn dark.
Vitamin C (ascorbic acid) is a strong reducer, so it reduces iodide to colorless iodide ions. Then the iodide ions reduce the hydrogen peroxide, and iodide forms again, which reacts with starch, forming a dark blue iodine-starch complex.