How to make potassium iodide

Making potassium iodide from elemental iodine and potassium hydroxide

Scientific name: Potassium hydroxide and potassium iodide form the iodine

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Safety

Wear lab gloves and eye protection.

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

Reaction formula

Reagents

1. Iodine
2. Potassium hydroxide
3. Water

Step-by-step instruction

1. Pour some water into a flask and dissolve some potassium hydroxide in it.
2. Put iodine crystals into the flask and heat it with a burner. All iodine should dissolve and react with potassium hydroxide. If the solution becomes brown there is an excess of iodine. In this case just add more potassium hydroxide.
3. Cool the flask down. Potassium iodate precipitates in the cold solution.
4. Filter potassium iodate.
5. Boil a little bit of the filtered solution and repeat the precipitating of potassium iodate.

Scientific background

Iodine reacts with potassium hydroxide forming potassium iodide (KI) and potassium iodate (KIO₃). This is the disproportionation reaction.

Because potassium iodate is much less soluble in water than potassium iodide it is possible to separate these two substances using the precipitation of potassium iodate from the solution.

Read more

1. How to Make Potassium Iodide (KI) from Elemental Iodine (I) and Potassium Hydroxide (KOH)
2. Способ получения йодида калия