Sublimation of iodine

Crystals become a vapor!

Scientific name: Iodine is sublimed under heating and recrystallized again under cooling.


Example of Sublimation: Iodine

by Wayne Breslyn

VIDEO 5 Sublimation of Iodine


Chemistry experiment 47 - Sublimation of Iodine

by koen2all

Sublimation of iodine demonstration

by Royal Society Of Chemistry



Sublimation of Iodine Crystals

by Yeo Yong Kiat

Physical Properties of Iodine

by NCSSMDistanceEd


Wear eye protection and gloves. Work in fume hood or outdoors.

Always follow general safety recommendations. Please note that conducting chemistry experiments you must comply with the relevant legal procedures in your country.

Reaction formula

I2 (solid) -heating→ I2 (gas) -cooling→ I2 (solid)


  1. Iodine

Step-by-step instruction

  1. Put about half a spoon of iodine crystals to the beaker.
  2. Clamp the beaker to a stand. Place the gas burner under it.
  3. Clamp the round-bottom flask on the stand above the beaker. The mouth of beaker should be closed by flask bottom.
  4. Pour ice-cold water into the flask.
  5. Heat the beaker with the gas burner.
  6. Iodine sublimes and recrystallizes on the flask bottom.

Scientific background

In this experiment solid iodine is vaporized without passing through a liquid state. The process of solid phase conversion directly to the gas phase is called sublimation. Each substance at given pressure and temperature possess one of the three main states: solid, liquid or gaseous. Temperature or pressure change can lead to appropriate phase transition.

The dependency of the substance state on temperature and pressure could be represented by a phase diagram. A phase diagram is type of chart that describes the conditions at which distinct phases can occur in equilibrium. A typical phase diagram has “y-like” shape. On a phase diagram one can find a special point – triple point – at which solid, vapor and liquid can coexist in thermodynamic equilibrium.

Sublimation takes place at temperatures and pressures below the substance triple point. When iodine crystals are heated, the temperature increases and we shift along the abscissa axis from the area of the phase diagram corresponding to solid state to the area corresponding to gas.

Cooling causes the reverse transition. When iodine vapors reach the bottom of the flask with ice-cold water they recrystallize. The reverse process of direct solid phase formation from vapors is called desublimation or decomposition.


Published on 23 April 2015

  • Fire
  • Heating with fire
  • Explosion
  • Poisoned gas
  • Organic
  • Electricity
  • Solution
  • Oxidation reduction
  • Color change
  • Precipitate
  • Gassing
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