What is potassium iodide and what is it used for?

Potassium iodide is most commonly talked about in the context of the treatment of thyroid problems and the hazards of radioactive contamination. However, this popular chemical has a much wider spectrum of action. What should we know about potassium iodide, and what are its properties and uses? Here is a summary of the key facts.

Published: 10-05-2022

Kl, or potassium iodide: what is it?

Although potassium iodide was invented as early as the beginning of the nineteenth century, it generated a huge amount of interest and publicity only after the 1986 disaster at the Chernobyl nuclear power plant. The product, abbreviated as Kl or bearing the name Kalii iodidum or Kalium iodatum, was an ingredient of Lugol’s iodine which blocks the effects of harmful radioactive isotopes of iodine.

What is potassium iodide? It is an inorganic chemical substance, also known as potassium salt of hydriodic acid. It is manufactured under laboratory conditions primarily for the pharmaceutical industry as an additive to medicines, ointments, liquids and dietary supplements.

Potassium iodide: physico-chemical properties

Potassium iodide is an odourless, non-flammable, water-soluble chemical substance with a salty bitter taste. It is in the form of fine white crystals, and it may also be transparent. What else should we know about it and what are its properties? Here are the key facts:

  • the density of potassium iodide is 3.12 g/cm3,
  • the melting point of Kl is 681°C, and its boiling point is 1323°C,
  • potassium iodide is also dissolved in ethanol and glycerol.

Potassium iodide solution is a substance that does not tolerate changes in environmental conditions well. When it is overheated and subjected to moisture, it causes corrosion of metals and produces harmful hydrogen and nitrogen oxides. After it is dissolved in water or when it evaporates, the Kl solution demonstrates corrosive properties: it irritates the skin, nasal mucosa and the eyes and disturbs the digestive system, causing a range of gastrointestinal problems.

Potassium iodide – application in medicine and more

Today, potassium iodide is very widely used in many industries. It is primarily used for the production of medicines, disinfectant liquids and dietary supplements (Lugol’s iodine, iodine). As a medicinal product, potassium iodide has versatile effects on the human body:

  • it protects the thyroid,
  • it has an anti-inflammatory effect,
  • it shows an expectorant effect,
  • it helps in the treatment of sporotrichosis, a fungal infection of the skin (potassium iodide has a damaging effect on the pathogenic fungi Sporothrix schenckii).

When consumed in excess, potassium iodide has an adverse effect on the human body: it can cause swelling, nausea and allergic reactions, and even depressive disorders! Therefore, it is obligatory to consult a doctor or pharmacist before starting potassium iodide treatment.

What are some other uses of potassium iodide? This inorganic compound is used, among other things, for:

  • iodination of table salt,
  • treatment of drinking water,
  • quantitative chemical analyses (known as titration),
  • physical analyses (spectroscopy),
  • qualitative analyses of food products (potassium iodide solution facilitates starch content detection),
  • production of light-sensitive photographic emulsion.

Lugol’s iodine – a solution of potassium iodide

In 1829, Jean Lugol, a French researcher and physician, created a recipe for an aqueous solution of potassium iodide (Solutio Iodi aquosa), which still functions today under the name Lugol’s iodine. Jean Lugol discovered that the combination of distilled water, iodine and potassium iodide has a very beneficial effect on hypothyroid patients and improves the function of the thyroid. Regular administration of the liquid was also supposed to protect this sensitive organ from carcinogenic radiation.

Today, Lugol’s iodine is manufactured on an industrial scale as a popular medicine, as well as a disinfectant and antibacterial agent. However, the beneficial effect of the liquid can only be achieved with the right dosage – the acceptable daily doses should always be determined by a doctor.

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