Sodium iodide
[CAS# 7681-82-5]

Identification

• Classification: Inorganic chemical industry >> Inorganic salt >> Metal halides and halides >> Metal iodide and salt
• Name: Sodium iodide
• Molecular Formula: NaI
• Molecular Weight: 149.89
• CAS Registry Number: 7681-82-5
• EC Number: 231-679-3
• SMILES: [Na+].[I-]

Properties

• Density: 3.667 g/mL (25 °C)
• Melting point: 661 °C
• Index of Refraction: 1.7745
• Boiling point: 1300 °C
• Water solubility: 184 g/100 mL (25 °C)

Safety Data

• Hazard Symbols: GHS07;GHS08;GHS09 Danger
• Risk Statements: H315-H319-H335-H372-H400
• Safety Statements: P260-P261-P264-P264+P265-P270-P271-P273-P280-P302+P352-P304+P340-P305+P351+P338-P319-P321-P332+P317-P337+P317-P362+P364-P391-P403+P233-P405-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Eye irritation	Eye Irrit.	2	H319
Skin irritation	Skin Irrit.	2	H315
Acute hazardous to the aquatic environment	Aquatic Acute	1	H400
Specific target organ toxicity - repeated exposure	STOT RE	1	H372
Specific target organ toxicity - single exposure	STOT SE	3	H335
Specific target organ toxicity - repeated exposure	STOT RE	2	H373
Reproductive toxicity	Repr.	2	H361
Chronic hazardous to the aquatic environment	Aquatic Chronic	2	H411
Chronic hazardous to the aquatic environment	Aquatic Chronic	1	H410
Eye irritation	Eye Irrit.	2A	H319
Acute toxicity	Acute Tox.	4	H302
Skin sensitization	Skin Sens.	1	H317
Skin corrosion	Skin Corr.	1B	H314

Discovery and Applications

Sodium iodide (NaI) is an ionic compound formed from sodium and iodine, consisting of white, hygroscopic crystals that are highly soluble in water. The discovery of sodium iodide dates back to the early 19th century, specifically in 1811, when it was first isolated by the French chemist Bernard Courtois during his experiments with iodine extraction from seaweed. Courtois found that when iodine reacted with sodium compounds, it yielded sodium iodide. This marked a significant development in the understanding of halides and their applications.

Sodium iodide has several important applications across various fields, particularly in medicine, industry, and research. One of its primary uses is in nuclear medicine. Sodium iodide, specifically in its radioactive form, sodium iodide-131 (NaI-131), is widely used for diagnostic imaging and treatment of thyroid conditions. NaI-131 emits radiation, which is utilized in both diagnostic and therapeutic procedures for hyperthyroidism and certain types of thyroid cancer. This isotope is preferentially absorbed by the thyroid gland, allowing for targeted treatment of thyroid disorders.

In addition to its medical applications, sodium iodide serves as a reagent in analytical chemistry. It is commonly used in iodometric titrations to determine the concentration of oxidizing agents in various samples. Its ability to form stable complexes with certain metals enhances its effectiveness in analytical techniques, making it an invaluable tool in laboratory settings.

Sodium iodide is also employed in the synthesis of other chemical compounds. It serves as a source of iodide ions in organic synthesis, facilitating the formation of iodinated products. This application is particularly relevant in the pharmaceutical industry, where sodium iodide is used to produce iodinated compounds that exhibit therapeutic properties.

Furthermore, sodium iodide plays a role in the food industry, where it is utilized as an iodizing agent for table salt. The addition of sodium iodide to salt is an essential public health measure aimed at preventing iodine deficiency, which can lead to serious health issues, including goiter and cognitive impairments. The iodization of salt has significantly improved the iodine status of populations worldwide, reducing the prevalence of iodine deficiency disorders.

Safety considerations are important when handling sodium iodide. While it is generally recognized as safe for consumption in appropriate amounts, excessive intake may lead to thyroid dysfunction or allergic reactions. Proper storage and handling procedures should be observed to prevent accidental exposure or misuse.

In summary, sodium iodide is a significant chemical compound with a rich history of discovery and diverse applications in medicine, analytical chemistry, and public health. Its role in addressing iodine deficiency and facilitating medical treatments underscores its importance in various scientific and industrial contexts.

References

2003. Evolutionary adaptation of a mammalian species to an environment severely depleted of iodide. Pflügers Archiv - European Journal of Physiology, 445(6).
DOI: 10.1007/s00424-002-0972-0

2003. Iodine-Induced Thyroid Disease. Diseases of the Thyroid.
DOI: 10.1007/978-1-59259-352-1_17

2003. Dual method for the determination of peroxidase activity and total peroxides-iodide leads to a significant increase of peroxidase activity in human sera. Analytical Biochemistry, 316(2).
DOI: 10.1016/s0003-2697(02)00652-8