How to make Purple Smoke

Smoke is generated in a lot of chemical reactions, but have you ever created purple smoke? Here is how!

Key Takeaways

  • This experiment deals with toxic chemicals, use proper Protection
  • The purple “smoke” is actually no smoke, but iodine vapor
  • During the reaction, a lot of heat is produced and occasionally sparks can be seen
  • 2Al + 3I2 -> 2AlI3 

What you will need to turn Smoke purple

The experiment preparation is quite easy. Please work outside or in a fume hood, since a lot of iodine vapor is produced. 

Make the Purple Smoke

  1. Separately powder the aluminum and iodine, using a mortar and pestle
  2. Mix the ingredients in the dish
  3. Place the dish on a fireproof work surface
  4. When ready, add a few drops of water to the reaction mixture. It takes a few seconds until the reaction evolves

What makes the smoke purple

Before adding water, the mixture of aluminum and iodine does not react on its own, because aluminum is covered by a protective oxide layer. This effect is called passivation. By adding water, some of the iodine dissolves to form hydroiodic and hypoiodous acids, which then penetrate the oxide film of the aluminum.

The reaction between aluminum and iodine kicks off and releases a large amount of heat. This heat is enough to vaporize the remaining iodine to form the purple vapor we see. Iodine stains can be removed by using an ascorbic acid solution. Ascorbic acid, also known as vitamin C, is an essential antioxidant needed by the human body.

Safety & Disposal

Any remaining iodine has to be reduced to iodide. This can be done with ascorbic acid or sodium dithionite solution. After adjusting the pH to around 7, the iodide solution can be poured down the drain. The disposal requirements may differ in your country.

During the experiment, large amounts of iodine vapours are released. Iodine is toxic. Only perform this experiment outside or in a fume hood. Wear skin and eye protection.

GHS H&P: H(312+332, 315, 319, 335, 372, 400) – P(273, 302+352, 305+351+338, 314)

The use of this instruction and the information provided therein takes place at the user’s own risk.