- Cadmium iodide (CdI₂) is an inorganic compound consisting of cadmium and iodine, and it belongs to the family of cadmium halides.
- In its pure form, it appears as a white or pale-yellow crystalline solid that is highly soluble in water and also dissolves in alcohol, acetone, and other polar solvents. The compound is hygroscopic, readily absorbing moisture from the air, and should be stored in airtight containers to maintain stability.
- CdI₂ is notable for its layered crystal structure, which is different from the cubic fluorite structure of cadmium fluoride but similar to cadmium chloride and cadmium bromide. In this arrangement, each cadmium ion (Cd²⁺) is coordinated by six iodide ions (I⁻) in an octahedral geometry, forming sheets that are held together by relatively weak van der Waals forces. This layered nature gives CdI₂ unique physical properties, including softness and ease of cleavage along specific planes.
- Cadmium iodide can be prepared by the direct combination of cadmium metal and iodine at elevated temperatures, yielding the anhydrous form. Alternatively, it can be synthesized by dissolving cadmium oxide, cadmium carbonate, or cadmium hydroxide in hydroiodic acid, followed by crystallization. The anhydrous compound is often sought after for specialized chemical synthesis, while hydrated forms are more commonly used in laboratory settings due to ease of preparation.
- CdI₂ has historically been used in photography, particularly in the preparation of silver iodide emulsions for photographic plates and films. It has also served as a catalyst or reagent in organic synthesis and as a precursor for other cadmium-containing compounds. In materials research, CdI₂ has attracted attention for its semiconductor properties, including a relatively wide bandgap, making it of interest for certain optoelectronic and detector applications. Furthermore, because of its layered crystal structure, CdI₂ is sometimes used in studies of two-dimensional materials and solid-state chemistry.
- Despite its technological and research value, cadmium iodide is highly toxic, with health risks similar to those of other soluble cadmium salts. Cadmium is a bioaccumulative heavy metal that can cause severe kidney damage, bone demineralization, respiratory problems, and has been classified as a human carcinogen. Inhalation of dust or ingestion of even small amounts can be dangerous. Consequently, handling CdI₂ requires strict safety protocols, including the use of gloves, protective eyewear, and well-ventilated environments or fume hoods.
- The environmental risks of cadmium iodide are also significant. Improper disposal can lead to contamination of soils and water systems, where cadmium persists and enters the food chain through plants and aquatic life. This persistence poses a threat to ecosystems and human health alike. Many countries have strict regulatory controls on the use, storage, and disposal of cadmium iodide, and hazardous waste procedures must be followed to prevent long-term environmental damage.
