Potassium iodide
[CAS# 7681-11-0]

Identification

• Classification: API >> Hormone and endocrine-regulating drugs >> Thyroid hormone and antithyroid drugs
• Name: Potassium iodide
• Molecular Formula: KI
• Molecular Weight: 165.99
• CAS Registry Number: 7681-11-0
• EC Number: 231-659-4
• SMILES: [K+].[I-]

Properties

• Density: 3.13 g/mL (20 °C)
• Melting point: 680 °C
• Index of Refraction: 1.677
• Boiling point: 1330 °C
• Water solubility: 144% w/w (water, 20 °C)

Safety Data

• Hazard Symbols: GHS07;GHS08;GHS09 Danger
• Risk Statements: H302-H315-H317-H319-H334-H372-H373-H411
• Safety Statements: P233-P260-P261-P264-P264+P265-P270-P271-P272-P273-P280-P284-P301+P317-P302+P352-P304+P340-P305+P351+P338-P319-P321-P330-P332+P317-P333+P317-P337+P317-P342+P316-P362+P364-P391-P403-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Specific target organ toxicity - repeated exposure	STOT RE	1	H372
Eye irritation	Eye Irrit.	2	H319
Skin irritation	Skin Irrit.	2	H315
Skin sensitization	Skin Sens.	1	H317
Acute toxicity	Acute Tox.	4	H302
Chronic hazardous to the aquatic environment	Aquatic Chronic	2	H411
Respiratory sensitization	Resp. Sens.	1	H334
Specific target organ toxicity - repeated exposure	STOT RE	2	H373
Specific target organ toxicity - single exposure	STOT SE	3	H335
Reproductive toxicity	Repr.	1B	H360
Reproductive toxicity	Repr.	2	H361
Chronic hazardous to the aquatic environment	Aquatic Chronic	1	H410
Acute toxicity	Acute Tox.	4	H312
Specific target organ toxicity - repeated exposure	STOT RE	2	H372
Carcinogenicity	Carc.	2	H351
Skin sensitization	Skin Sens.	1B	H317
Specific target organ toxicity - single exposure	STOT SE	1	H370

Discovery and Applications

Potassium iodide (KI) is a white, crystalline salt that is highly soluble in water. It is an essential source of iodine, an element crucial for human health and various industrial applications. The discovery of potassium iodide dates back to the early 19th century. In 1811, the French chemist Bernard Courtois isolated iodine from seaweed and later discovered that this element could form salts with various cations, including potassium. By reacting iodine with potassium carbonate, Courtois successfully synthesized potassium iodide, leading to further studies on its properties and uses.

The applications of potassium iodide are diverse and significant. One of its most well-known uses is in medicine. Potassium iodide is employed as a supplement to prevent iodine deficiency, which can lead to conditions such as goiter and thyroid dysfunction. The human body requires iodine to produce thyroid hormones, and potassium iodide provides an effective means of supplementation. Additionally, it is used in the treatment of hyperthyroidism and certain thyroid disorders, as it can help reduce the production of thyroid hormones.

Another critical application of potassium iodide is its role in radiation safety. In the event of a nuclear accident or exposure to radioactive iodine, potassium iodide can be administered as a protective measure. It works by saturating the thyroid gland with stable iodine, thereby reducing the absorption of radioactive isotopes. This application has been emphasized in emergency preparedness plans in areas near nuclear power plants and during nuclear emergencies.

Potassium iodide also finds use in various industrial applications. It is commonly used as a photographic chemical in the preparation of certain photographic films and papers. Its ability to form complexes with silver ions makes it valuable in developing photographs, enhancing image quality. Furthermore, potassium iodide serves as a reagent in analytical chemistry for iodometric titrations, where it is used to determine the concentration of oxidizing agents.

In the field of food industry, potassium iodide is added to table salt as a means of iodization, helping to prevent iodine deficiency in populations. This practice is particularly important in regions where natural dietary iodine is low. The introduction of iodized salt has significantly improved public health by reducing the incidence of iodine deficiency-related disorders.

Despite its numerous beneficial applications, safety considerations are essential when handling potassium iodide. While it is generally regarded as safe when used appropriately, excessive consumption can lead to adverse effects, including thyroid dysfunction and allergic reactions. Therefore, proper dosage and usage guidelines should be followed to mitigate potential health risks.

In summary, potassium iodide is a versatile chemical compound with a rich history of discovery and a wide range of applications in medicine, radiation safety, industry, and public health. Its importance in both historical and contemporary contexts underscores its value in various fields, particularly in promoting human health and safety.

References

2025. Immunophenotyping of Hematopoietic Cells in the Spleen in Hypothyroid Mice. Methods in molecular biology (Clifton, N.J.), 2855.
DOI: 10.1007/978-1-0716-4252-8_7

2025. Generation of a Mouse Model for the Study of Thyroid Hormones Regulatory Effect on the Immune System. Methods in molecular biology (Clifton, N.J.), 2855.
DOI: 10.1007/978-1-0716-4252-8_4

2024. Risk factors and clinical characteristics associated with post-radioactive iodine thyroid storm. Thyroid Research, 17(1).
DOI: 10.1186/s13044-024-00217-4