Equipment needed to conduct the experiment known as elephant's toothpaste. From left to right are: a conical flask, potassium iodide solution, hydrogen peroxide solution, two bottles of food dye and liquid soap. The experiemnt is a demonstration of the rapid decomposition of hydrogen peroxide. A 30% solution of hydrogen peroxide is placed in a conical flask, along with some liquid soap and food colouring. When a catalyst such as potassium iodide is added, the hydrogen peroxide rapidly decomposes to water and oxygen. The oxygen is trapped as bubbles in the liquid soap and foams out of the flask.