Potassium chlorate, beautiful but dangerous

Investigators probing the cause of the fireworks disaster at the Puttingal Devi temple near Kollam on Sunday, hinted that rival teams possibly used potassium chlorate, a banned explosive.

They had also probably sourced the chemical illegally from matchstick factories.

Potassium chlorate was discovered by French chemist Claude Louis Berthollet during the end of the 18th Century.

Use in pyrotechnics

The principal reason for using it in pyrotechnics is for the production of beautiful colours. Despite its inherent risk, the reason it is sometimes used in pyrotechnics is because it is cheap and easily available.

How does it work?

According to the Royal Society of Chemistry, potassium chlorate has very powerful oxidising ability. When heated, it decomposes to produce oxygen.

The oxygen so produced fuels the flame of the lit firework, thereby increasing the temperature of the firework even further.

The extra heat generated excites the electrons in the colour-producing chemicals added in the firework mixture and thus produces beautiful colours.

The oxidising property of potassium chlorate is also its biggest disadvantage when used in fireworks. It has an inherent property to become very reactive, especially when mixed with sulphur; the potassium chlorate-sulphur mixture becomes dangerously sensitive to friction and may spontaneously ignite.

Hence, potassium chlorate is banned for use in fireworks.

Limited use

Despite the risks, potassium chlorate is relatively safe when used in tiny amounts. It is used along with sand and red phosphorus in caps for use in toy guns. When the cap is struck by a metal head of the gun, friction is generated that ignites the red phosphorus. The heat generated by the burning red phosphorus triggers the decomposition of the potassium chlorate. The oxygen released by potassium chlorate further assists the burning of the red phosphorus. The end result is the sound.

The same principle is used in safety matches.Matchstick head contains tiny amount of potassium chlorate, antimony sulphide and powdered glass. When matchsticks are struck, the friction generated ignites the red phosphorus.