Potassium iodide

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Potassium iodide
IUPAC name
Potassium iodide
Systematic IUPAC name
Potassium iodide
Other names
Kali iodide
Molar mass 166.0028 g/mol
Appearance White solid
Odor Odorless
Density 3.12 g/cm3
Melting point 681 °C (1,258 °F; 954 K)
Boiling point 1,330 °C (2,430 °F; 1,600 K)
128 g/100 ml (0 °C)
140 g/100 ml (20 °C)
148 g/100 ml (25 °C)
176 g/100 ml (60 °C)
206 g/100 ml (100 °C)
Solubility Slightly soluble in ammonia, diethyl ether, ethanol
Solubility in acetone 1.31 g/100 ml (25 °C)
Solubility in ethanol 1.88 g/100 ml (25 °C)
Solubility in glycerol 40 g/100 ml
Solubility in methanol 12.5 g/100 ml
Safety data sheet Sigma-Aldrich
Flash point Non-flammable
Related compounds
Related compounds
Sodium iodide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Potassium iodide is the inorganic ionic compound with the chemical formula KI. It is a clear crystalline salt that serves as a convenient source of iodine.



When treated with a strong acid such as hydrochloric acid, hydroiodic acid is formed, along with the potassium salt of the acid. A useful reagent in itself, hydroiodic acid can also be oxidized directly to elemental iodine with the addition of hydrogen peroxide. Potassium iodide, being water-soluble, is a useful source of the iodide ion in solution as well.

Potassium iodide is a very strong reducing agent. It reacts readily with any oxidizer, including oxidizing acids such as sulfuric and nitric. It may be desirable if you want to use it to reduce these acids, but undesirable if you want hydrogen iodide. To avoid unwanted redox reactions, use phosphoric acid, which is both non-volatile and exceptionally gentle to reducing agents.

Like most iodides, it will form dark brown triiodides on contact with elemental iodine.


At room temperature, potassium iodide follows the general pattern of alkali metal halides in that it appears as a colorless, odorless crystalline salt that is highly soluble in water.


Potassium iodide can be found as an iodine supplement or as an emergency medicine for radiation poisoning, which means it may be stocked by some survivalist/prepper outlets. It is easily purchased online.

Iodine tinctures are a solution of iodine with potassium iodide. Separating the latter however, is usually messy. Lugol's Iodine is a good source of potassium iodide. In USA, USP Strong Iodine Tincture contains potassium iodide, while USP Tincture of Iodine contains sodium iodide.


Potassium iodide can easily be synthesized by the action of elemental iodine or hydroiodic acid on potassium hydroxide.




Potassium iodide is a mild irritant, and due to the high mass percentage of iodine it contains, large amounts of exposure can effect the thyroid gland. It may also factor in causing birth defects.


Potassium iodide should be stored in closed containers. It will slowly give off iodine vapors, which will stain the inside of the container. Because of this, NEVER USE METAL CONTAINERS.


Potassium iodide can be poured down the drain.


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