Cadmium nitrate is an inorganic salt composed of cadmium cations (Cd2+) and nitrate anions (NO3−). In commerce and the laboratory it is most commonly encountered as colorless crystalline solids or hydrated forms. Because it contains the nitrate ion it can act as an oxidizing salt under some conditions; because it contains cadmium it is a toxic heavy‑metal compound with well‑documented health and environmental risks.
Composition and structure
The formal formula is Cd(NO3)2. As an ionic compound, cadmium(II) occupies coordination sites surrounded by nitrate anions and, in hydrated samples, by water molecules. Cadmium(II) typically adopts six‑coordinate geometries, and common isolated materials include hydrates such as the tetrahydrate. The nitrate groups are bonded as discrete anions rather than covalently linked frameworks.
Preparation and chemical behaviour
Cadmium nitrate is prepared by reacting cadmium metal, cadmium oxide, or cadmium carbonate with nitric acid to afford the soluble nitrate salt and water (and hydrogen in the case of metal dissolution). The salt is readily soluble in water, and in solution it provides free Cd2+ ions that participate in precipitation, complexation, and redox reactions. On heating it decomposes, releasing nitrogen oxides and leaving cadmium oxide or other cadmium residues.
Physical forms and properties
Commercial samples are normally white to colorless crystals that may be hygroscopic and form hydrates. They dissolve easily in water and other polar solvents to give clear solutions. The solid and its solutions are oxidizing to varying degrees due to the nitrate anion, and the compound will react with bases to yield cadmium hydroxide or with sulfide sources to produce cadmium sulfide, a brightly colored pigment.
Uses and examples
- Laboratory reagent: as a soluble source of Cd2+ for synthesis and analysis.
- Precursor to other cadmium compounds: used to prepare sulfides, oxides, and salts by precipitation or thermal decomposition.
- Historical or specialty applications: in pigments and plating processes where cadmium compounds are required (use is now restricted in many applications because of toxicity).
Safety, environmental impact, and handling
Cadmium nitrate poses significant health hazards. Cadmium and many cadmium compounds are classified as carcinogenic and are known to cause kidney damage and bone effects on chronic exposure. The material should be handled in a fume hood with gloves and eye protection, avoiding inhalation and skin contact. Spills require containment and disposal as hazardous waste according to regulations. Environmentally, cadmium is persistent and bioaccumulative, so releases to soil and water are tightly regulated in many jurisdictions.