Potassium iodide (KI) structure, properties, obtaining, uses, risks

The potassium iodide is an inorganic compound formed by a potassium ion (K⁺) and an iodide ion (I^-). Its chemical formula is KI. It is a white crystalline solid, ionic in nature and very soluble in water..

KI enables various chemical reactions and analyzes to be carried out and is used to measure the amount of ozone in the atmosphere. Also used in infrared (IR) analysis equipment.

Potassium iodide is added to common table salt to prevent iodine deficiency in people, as this can be a serious health problem.

It is used as an expectorant as it helps mucus to flow easily from the respiratory channels to the outside. It is also used to treat some fungal infections and is used in some cosmetics.

It is used by veterinary doctors to cure animals from human-like problems such as coughs and skin infections. It is even added in very small amounts to animal feed.

Article index

• 1 Structure
• 2 Nomenclature
• 3 Properties
  • 3.1 Physical state
  • 3.2 Molecular weight
  • 3.3 Melting point
  • 3.4 Boiling point
  • 3.5 Density
  • 3.6 Solubility
  • 3.7 pH
  • 3.8 Chemical properties
  • 3.9 Other properties
• 4 Obtaining
• 5 Uses
  • 5.1 In the treatment of hyperthyroidism
  • 5.2 In other medical applications
  • 5.3 In veterinary applications
  • 5.4 In protecting the thyroid gland in radioactive emergencies
  • 5.5 In measurements of ozone in the atmosphere
  • 5.6 In various uses
• 6 Risks
• 7 References

Structure

Potassium iodide is an ionic compound formed by the potassium cation K⁺ and the iodide anion I^-, therefore, between the two the bond is ionic. The oxidation state of potassium is +1 and the valence of iodine is -1.

KI potassium iodide crystals are cubic.

Nomenclature

- Potassium iodide

- Potassium iodide

Properties

Physical state

Colorless to white crystalline solid. Cubic crystals.

Molecular weight

166.003 g / mol

Melting point

681 ºC

Boiling point

1323 ºC

Density

3.13 g / cm³

Solubility

Very soluble in water: 149 g / 100 g of water at 25 ° C. Slightly soluble in ethanol and ether.

pH

Its aqueous solutions are neutral or alkaline, with a pH between 7 and 9.

Chemical properties

Slightly hygroscopic in humid air.

It is stable in dry air. Light and moisture accelerate its decomposition and its color changes to yellow due to the release of small amounts of iodine (I_two) and iodates (IO₃^-).

Aqueous KI solutions also turn yellow over time, however a little alkali can prevent this.

These solutions dissolve iodine (I_two) giving KI₃:

I^- + I_two → I₃^-

Other properties

It has a strongly bitter and saline taste. It is not flammable.

Obtaining

Potassium iodide can be obtained by heating iodine (I_two) in a concentrated solution of potassium hydroxide (KOH):

3 I_two + 6 KOH → 5 KI + KIO₃ + H_twoOR

The resulting iodate and iodide solution is heated to remove water, reduced to dryness, charcoal is added, and heated to high temperature. Coal takes oxygen from iodate and oxidizes to carbon dioxide thus reducing iodate to iodide:

2 KIO₃ + C → 2 KI + 3 CO_two

The potassium iodide obtained can be recrystallized for purification. That is, it redissolves in water and is induced to crystallize again..

Applications

In the treatment of hyperthyroidism

Potassium iodide serves as an additional treatment along with other antithyroid agents to treat hyperthyroidism.

Hyperthyroidism is a disease that causes the thyroid gland to produce too much thyroid hormone, with an enlarged thyroid, a decrease in weight, a fast heartbeat, and irritability, among other symptoms..

In patients with hyperthyroidism, KI rapidly reduces symptoms as it inhibits the release of thyroid hormone.

Its effects on the thyroid are: a decrease in the number of blood vessels in the gland, firming its tissues and reducing the size of its cells..

For this reason, it is applied as a preoperative treatment to induce the involution or decrease in size of the thyroid before a thyroidectomy (removal of the thyroid) as this facilitates this operation..

In other medical applications

Potassium iodide has expectorant properties as it increases the secretion of respiratory fluids, resulting in a decrease in mucus viscosity..

It is used to treat erythema nodosum, which is a painful swelling in the legs in which red nodules form and an increase in temperature.

It is an antifungal agent. It allows treating sporotrichosis which is a skin infection caused by a fungus. This disease happens to people who work with plants and soil, such as farmers and gardeners..

It is also used in the treatment of iodine deficiency or to avoid it and therefore it is added to table salt or edible salt (sodium chloride NaCl) as a source of iodine and sometimes in drinking water.

In veterinary applications

Potassium iodide is administered to animals as an antitussive, to increase and liquefy the fluids of the respiratory tract, for chronic bronchial cough, as well as in cases of rheumatism and as an anti-inflammatory.

It is also used for mycosis (fungal infections) of animals, to reduce itching and for chronic poisoning with lead or mercury.

In protecting the thyroid gland in radioactive emergencies

Potassium iodide has thyroid protective properties in the event that the person has been exposed to nuclear radiation.

KI floods the thyroid with non-radioactive iodine thus blocking the uptake of radioactive molecules and the absorption of radioactive iodine, protecting the thyroid gland from cancer that radiation can cause..

In measurements of ozone in the atmosphere

Ozone gas (O₃) can be measured in the atmosphere using electrolytic cells called ozonesondes, which are carried by radiosonde balloons.

These electrolytic cells contain a KI potassium iodide solution. Cells are initially in chemical and electrical equilibrium.

When an ozone air sample (O₃) penetrates one of the cells, the equilibrium is broken because the following reaction occurs:

2 KI + O₃ + H_twoO → I_two + OR_two + 2 KOH

This reaction produces an electrical current that flows between the cells..

The amount of electrical current produced is continuously transmitted by radio waves to a station on the ground. In this way, the ozone profile from the ground to the height of the ball is obtained..

In various uses

Potassium iodide also allows:

- Elimination of free radicals such as the hydroxyl radical OH^.

- The manufacture of photographic emulsions, to precipitate silver.

- Improve animal feed by being added in micro quantities.

- Deodorize livestock manure.

- Transmit the light of the infrared spectrum in IR analysis equipment.

- Perform certain chemical reactions and analysis in chemistry laboratories.

- Use it in personal hygiene products.

- Perform environmental contamination analysis.

Risks

Some people sensitive to iodides should take it with caution as it can cause iodism, or chronic iodine poisoning, for example those with an autoimmune thyroid disease.

People with tuberculosis or acute bronchitis should also be careful.

KI can cause softening of the salivary glands, it can burn the mouth or throat, unusual increase in salivation, tooth pain and inflammation of the gums and metallic taste, among other symptoms..

It can also irritate the eyes and open wounds on the skin..

References

1. U.S. National Library of Medicine. (2019). Potassium iodide. Recovered from pubchem.ncbi.nlm.nih.gov.
2. Kirk-Othmer (1994). Encyclopedia of Chemical Technology. Fourth Edition. John Wiley & Sons.
3. Dean, J.A. (editor). (1973). Lange's Handbook of Chemistry. Eleventh Edition. McGraw-Hill Book Company.
4. Valkovic, V. (2019). Decontamination after radiation exposure. Most sensitive body parts. In Radioactivity in the Environment (Second Edition). Recovered from sciencedirect.com.
5. Smit, H.G.J. (2015). Chemistry of the Atmosphere-Observations for Chemistry (In Situ). In Encyclopedia of Atmospheric Sciences (Second Edition). Recovered from sciencedirect.com.
6. Muralikrishna, I.V. and Manickam, V. (2017). Analytical Methods for Monitoring Environmental Pollution. In Environmental Management. Recovered from sciencedirect.com.
7. Wallace, J.M. and Hobbs, P.V. (2006). Atmospheric Chemistry 1. In Atmospheric Science (Second Edition). Recovered from sciencedirect.com.