Chemical Tips Sharing – Potassium Iodide

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Chemical formula KI. Colorless crystals or white powder, with a strong bitter-salty taste; slightly deliquescent. Density: 3.13 g·cm-3; melting point: 681°C; boiling point: 1,330°C. Soluble in water, ethanol, propanol, and glycerin; insoluble in ether. Potassium iodide can be obtained by reacting iodine with potassium hydroxide, and then reducing the resulting potassium iodate using formic acid (or charcoal): 6KOH + 3I2 → 5KI + KIO3 + 3H2O. KIO3 + 3HCOOH → KI + 3CO↑ + 3H2O. Potassium iodide slowly releases iodine when exposed to air (or light), causing it to turn yellow; this reaction occurs more rapidly in aqueous solutions, especially in acidic media. 4I- + O2 + 4H+ → 2I2 + 2H2O. Potassium iodide is a raw material for the production of iodides and dyes. In solution, potassium iodide readily forms potassium triiodide with iodine. Potassium iodide is a cosolvent for iodine and certain insoluble metal iodides. Medically, potassium iodide is used as an expectorant, as well as a medication to prevent goiter and hyperthyroidism prior to surgery. It is also a commonly used reagent in chemical analysis.