Cadmium nitrate
Cadmium nitrate is an inorganic compound with the chemical formula Cd(NO₃)₂, existing most commonly as the tetrahydrate Cd(NO₃)₂·4H₂O, which forms colorless to white, deliquescent crystals that readily absorb moisture from the air.[1][2] It has a molecular weight of 236.42 g/mol for the anhydrous form and 308.48 g/mol for the tetrahydrate, with a density of 2.45 g/cm³ for the tetrahydrate.[1][2] The compound is highly soluble in water, ethanol, and acetone, and decomposes upon heating to produce toxic cadmium oxide fumes.[1][3] Physically, the tetrahydrate form of cadmium nitrate melts at 59.5°C and boils at 132°C, though it is nonflammable yet acts as a strong oxidizing agent, potentially intensifying fires and reacting explosively with reducing agents like phosphorus or alkyl esters.[1][4] Chemically, it is stable under normal conditions but hazardous in combustion, releasing toxic nitrogen oxides and cadmium oxide.[4] Its high solubility in water facilitates rapid absorption, contributing to its acute toxicity profile.[4] Cadmium nitrate finds applications in imparting a reddish-yellow luster to glass and porcelain, in the preparation of photographic emulsions, and as a laboratory reagent for various chemical syntheses.[1] However, due to the inherent toxicity of cadmium, it is classified as a carcinogen, mutagen, and reproductive toxicant, with exposure routes including inhalation, ingestion, and skin contact leading to severe effects such as irritation of the eyes, skin, and respiratory tract, gastrointestinal distress, kidney and liver damage, pulmonary edema, and long-term risks of emphysema and cancer.[5][1] Regulatory limits restrict workplace exposure to as low as 0.005 mg/m³, and it is prohibited in cosmetics while requiring strict handling with personal protective equipment.[1][5]Properties
Physical properties
Cadmium nitrate exists primarily in two forms: the anhydrous compound with the chemical formula Cd(NO₃)₂ and the tetrahydrate Cd(NO₃)₂·4H₂O. The molar mass of the anhydrous form is 236.42 g/mol, while that of the tetrahydrate is 308.48 g/mol.[6][7] The compound appears as a colorless to white hygroscopic crystalline solid in both forms, readily absorbing moisture from the air.[8][9] The density of the anhydrous cadmium nitrate is 3.6 g/cm³, compared to 2.45 g/cm³ for the tetrahydrate measured at 17 °C.[9][3] The anhydrous form decomposes at approximately 360 °C without a distinct melting point, whereas the tetrahydrate melts at 59.5 °C and undergoes dehydration at 132 °C before further decomposition.[8][9] Cadmium nitrate exhibits high solubility in water, with the solubility increasing with temperature. The following table summarizes key solubility data for the tetrahydrate in water (approximate values in g/100 g water):| Temperature (°C) | Solubility (g/100 g water) |
|---|---|
| 0 | 123 |
| 25 | 158 |
| 30 | 166 |
| 60 | 210 |