- Cadmium perchlorate is an inorganic salt with the chemical formula Cd(ClO₄)₂, most commonly encountered as a hydrated form such as the hexahydrate Cd(ClO₄)₂·6H₂O.
- It consists of divalent cadmium cations (Cd²⁺) paired with perchlorate anions (ClO₄⁻). The perchlorate ion has a tetrahedral geometry, with a central chlorine atom covalently bonded to four oxygen atoms, carrying a net −1 charge.
- The anhydrous salt has a molar mass of 311.30 g/mol, while the hexahydrate is about 419.39 g/mol.
- Cadmium perchlorate typically appears as colorless, hygroscopic crystals that are readily soluble in water, producing strongly acidic solutions. It is also soluble in ethanol, methanol, and other polar organic solvents. The hydrated form often crystallizes in the monoclinic or orthorhombic system, with cadmium ions coordinated by oxygen atoms from both water molecules and perchlorate anions, forming distorted octahedral complexes.
- Being hygroscopic, it must be stored in airtight containers to prevent moisture uptake.
- Cadmium perchlorate can be prepared by neutralizing cadmium carbonate, cadmium oxide, or cadmium hydroxide with perchloric acid:
- CdCO₃ + 2 HClO₄ → Cd(ClO₄)₂ + CO₂↑ + H₂O
- CdO + 2 HClO₄ → Cd(ClO₄)₂ + H₂O
- The resulting solution can be concentrated and crystallized to yield the desired hydrated salt. Due to the strong oxidizing properties of perchloric acid, the reaction must be carried out under controlled conditions to avoid hazardous side reactions.
- Cadmium perchlorate is a strong oxidizing agent because of the perchlorate anion. While stable under normal conditions, it may react violently with organic matter, reducing agents, or flammable substances, especially when heated. Upon strong heating, it decomposes, releasing toxic cadmium oxide fumes and oxygen as well as potentially forming chlorine oxides:
- Cd(ClO₄)₂ → CdO + Cl₂ + O₂ + other Cl–O specie
- In aqueous solutions, it dissociates completely into cadmium cations and perchlorate anions.
- Cadmium perchlorate has limited commercial use due to its toxicity and oxidizing nature, but it is used in research and laboratory settings. It can serve as a catalyst or oxidizing agent in organic synthesis, a reagent in spectroscopic studies, and a source of cadmium ions in certain electrochemical processes. In coordination chemistry, cadmium perchlorate is often used as a starting material for preparing cadmium-based coordination complexes with organic ligands.
- Like all cadmium compounds, cadmium perchlorate is highly toxic and carcinogenic. It is harmful if inhaled, ingested, or absorbed through the skin. Acute exposure may cause severe irritation of the respiratory tract, gastrointestinal distress, and potential kidney injury. Chronic exposure leads to kidney damage, bone demineralization, and an increased risk of lung and prostate cancers. Additionally, perchlorate ions can interfere with iodine uptake in the thyroid, though the cadmium toxicity generally overshadows this effect.
- Cadmium perchlorate is highly toxic to aquatic life, persistent in the environment, and capable of bioaccumulation in the food chain. Release into waterways or soil can lead to long-term contamination. Due to the combined hazards of cadmium and perchlorate, its use and disposal are subject to strict environmental regulations. It must be handled in fume hoods, with all waste collected for hazardous waste disposal in accordance with chemical safety laws.
- It is classified as both a toxic substance and an oxidizer for transport and safety purposes. Internationally, it would generally be shipped under UN numbers relevant to perchlorates or cadmium compounds, such as UN 1481 – Perchlorates, inorganic, n.o.s., oxidizing solid, with hazard classes 5.1 (oxidizer) and 6.1 (toxic). Occupational exposure limits are the same as for other cadmium compounds—typically ≤0.005 mg/m³ (as Cd) for an 8-hour time-weighted average.
