Lead(II) iodide
Lead(II) iodide is an inorganic compound with the chemical formula PbI₂. It is a bright yellow, odorless, crystalline solid at room temperature. It is virtually insoluble in cold water, but its solubility increases with temperature. Lead(II) iodide is classified as a toxic substance due to the presence of lead.
Properties:
- Appearance: Bright yellow crystalline solid
- Odor: Odorless
- Melting Point: Approximately 402 °C (756 °F; 675 K)
- Boiling Point: Approximately 950 °C (1,742 °F; 1,223 K) (decomposes)
- Solubility: Insoluble in cold water, slightly soluble in hot water, soluble in solutions of alkali iodides.
- Crystal Structure: Hexagonal
Synthesis:
Lead(II) iodide is typically synthesized by reacting lead(II) nitrate or lead(II) acetate with potassium iodide or sodium iodide in an aqueous solution. A double displacement reaction occurs, precipitating lead(II) iodide as a yellow solid.
Pb(NO₃)₂ (aq) + 2 KI (aq) → PbI₂ (s) + 2 KNO₃ (aq)
Uses:
Lead(II) iodide has several applications, including:
- Pigment: Historically used as a yellow pigment, though its toxicity has limited this use.
- Photographic materials: Used in certain photographic processes.
- Thermoelectric materials: Investigated for use in thermoelectric devices.
- X-ray and gamma-ray detectors: Due to its high atomic number, it has been researched for radiation detection applications.
Safety:
Lead(II) iodide is toxic due to the presence of lead. Exposure can occur through inhalation, ingestion, or skin contact. It is a suspected carcinogen. Proper safety precautions, including wearing appropriate personal protective equipment (PPE) such as gloves, eye protection, and respiratory protection, should be taken when handling this compound. It should be handled in a well-ventilated area.
Storage:
Lead(II) iodide should be stored in a tightly closed container in a cool, dry, and well-ventilated area away from incompatible materials.