- Potassium iodide (chemical formula KI) is a white, crystalline, water-soluble ionic compound composed of potassium (K⁺) and iodide (I⁻) ions. It is a vital source of iodine in both health and industrial contexts and plays a significant role in medicine, nutrition, analytical chemistry, and radiation protection.
- When dissolved in water, potassium iodide dissociates completely into its constituent ions, making it readily bioavailable and chemically reactive in aqueous environments.
- In medicine, potassium iodide is best known for its role in thyroid protection during radiological emergencies. It works by saturating the thyroid gland with stable (non-radioactive) iodine, thereby preventing the uptake of radioactive iodine isotopes (like iodine-131) released during nuclear accidents or medical exposures. This protective action helps reduce the risk of thyroid cancer and other disorders. Because of this, potassium iodide tablets are stockpiled by public health agencies and distributed to populations at risk during nuclear events. It is also used in pre-operative treatment of hyperthyroidism, particularly in Graves’ disease, to reduce thyroid hormone release and gland vascularity.
- Potassium iodide has longstanding use as an iodine supplement, especially in the prevention and treatment of iodine deficiency disorders such as goiter and cretinism. In many countries, it is added in small amounts to table salt (known as iodized salt) to ensure adequate dietary iodine intake, which is critical for the synthesis of thyroid hormones.
- In the pharmaceutical and medical fields, potassium iodide also serves as an expectorant in certain cough medications. It helps thin mucus in the respiratory tract, facilitating its removal. In addition, it is sometimes used in dermatology to treat sporotrichosis, a fungal infection, and as an adjunctive therapy in cases of erythema nodosum or iodine-responsive dermatoses.
- In analytical chemistry, potassium iodide is commonly employed as a reducing agent and a component in iodometric titrations, especially in the determination of oxidizing agents such as chlorine and hydrogen peroxide. It reacts readily with these oxidizers to liberate elemental iodine, which can then be quantified using standard techniques.
- In industrial applications, potassium iodide is used in the preparation of photographic chemicals, dyes, and inks, and as an additive in animal feed to prevent iodine deficiency in livestock. It is also employed in the etching and polishing of metal surfaces, and in cloud seeding experiments to encourage precipitation.
- Although potassium iodide is generally safe when used within recommended limits, excessive intake can lead to adverse effects such as iodine-induced hyperthyroidism or hypothyroidism, skin rashes, gastrointestinal upset, and metallic taste. In rare cases, it can cause more serious allergic reactions. As with all iodine-containing compounds, caution is required for individuals with thyroid disorders or iodine sensitivity.
