- Cadmium sulfate (CdSO₄) is an inorganic compound consisting of cadmium in the +2 oxidation state combined with the sulfate anion (SO₄²⁻).
- In its anhydrous form, it is a white crystalline solid, but it also occurs in various hydrated forms, such as the monohydrate (CdSO₄·H₂O) and the octahydrate (CdSO₄·8H₂O). These hydrates are colorless, transparent crystals that are readily soluble in water, forming colorless solutions.
- Cadmium sulfate has been used historically in electroplating, pigments, and as a precursor in the preparation of other cadmium compounds, although its use has declined due to cadmium’s recognized toxicity.
- Cadmium sulfate can be prepared by dissolving cadmium metal, cadmium oxide (CdO), or cadmium carbonate (CdCO₃) in dilute sulfuric acid. The general reaction with the metal can be represented as:
- Cd + H₂SO₄ → CdSO₄ + H₂↑
- When prepared from oxide or carbonate, water and carbon dioxide are produced instead of hydrogen gas. The resulting solution can be evaporated to obtain crystals of cadmium sulfate in the desired hydrated form. Industrially, cadmium sulfate is also obtained as a byproduct in the refining of zinc ores, since cadmium occurs naturally in small amounts alongside zinc minerals.
- Chemically, cadmium sulfate is stable under normal storage conditions, but it decomposes at elevated temperatures to form cadmium oxide, sulfur dioxide, and oxygen. It is readily soluble in water and slightly soluble in methanol and ethanol. Aqueous solutions are acidic due to hydrolysis of the cadmium ion. CdSO₄ has been employed in electroplating baths to produce smooth, corrosion-resistant cadmium coatings, as well as in dyeing and printing textiles, and in certain battery electrodes. Its high solubility and ionic conductivity make it useful in electrochemical applications, though such uses are increasingly restricted.
- From a toxicological standpoint, cadmium sulfate is highly hazardous. Ingestion, inhalation, or skin absorption can lead to acute poisoning, with symptoms such as vomiting, diarrhea, abdominal pain, and severe kidney damage. Chronic exposure can result in cancer, bone demineralization, and irreversible organ damage due to cadmium’s tendency to bioaccumulate. As a soluble cadmium compound, CdSO₄ is particularly dangerous because it is more readily absorbed into the body than insoluble cadmium salts. Strict industrial hygiene, including the use of gloves, protective clothing, and fume hoods, is essential when handling this compound.
- Environmentally, cadmium sulfate is highly toxic to aquatic life and can persist in soils, contaminating water supplies and entering the food chain. Disposal requires careful neutralization and recovery of cadmium to prevent ecological damage. As a result, its production and use are heavily regulated in many countries, with research efforts focused on finding less hazardous alternatives.
