Sodium iodide (chemical formula: NaI) is an inorganic compound composed of sodium ions (Na?) and iodide ions (I?). The following is a detailed introduction to sodium iodide:

1. Physical Properties

- Appearance: Colorless or white crystalline solid, hygroscopic (absorbs moisture from the air).

- Melting point: 651°C.

- Boiling point: 1304°C.

- Solubility:

  - Highly soluble in water (approximately 184 g/100 mL at 20°C), aqueous solution is neutral.

  - Soluble in organic solvents such as ethanol.

4. Main Applications

- Medical field:

  - Treatment of iodine deficiency (e.g., thyroid disorders).

  - Used as a carrier for radioactive iodine (e.g., 131I) in thyroid function tests or cancer therapy.

- Chemical reagent:

  - Organic solutions of sodium iodide are used to detect organic chlorides/bromides.

  - Serves as an iodine source in analytical chemistry.

- Other applications:

  - Doped with thallium (Tl) to form scintillation crystals (NaI(Tl)), used for gamma-ray detection (e.g., nuclear medicine, security screening equipment).

5. Safety Precautions

- Toxicity: Low toxicity, but excessive intake may cause iodine poisoning (symptoms include nausea, thyroid dysfunction).

- Storage: Must be sealed and stored away from light (as it is hygroscopic and decomposes upon light exposure).

- Environmental: Avoid large-scale release, as it may be harmful to aquatic organisms.