Cadmium hydroxide is an inorganic compound with the formula Cd(OH)2. It is a white crystalline ionic compound that is a key component of nickel–cadmium battery.Karl-Heinz Schulte-Schrepping, Magnus Piscator "Cadmium and Cadmium Compounds" in Ullmann's Encyclopedia of Industrial Chemistry, 2007 Wiley-VCH, Weinheim. .
Structure Cadmium hydroxide adopts the same structure as Mg(OH)2, consisting of slabs of metal centers, each bonded by six hydroxide ligands.Hemmingsen, L.; Bauer, R.; Bjerrum, M. J.; Schwarz, K.; Blaha, P.; Andersen, P., "Structure, Chemical Bonding, and Nuclear Quadrupole Interactions of β-Cd(OH)2: Experiment and First Principles Calculations", Inorganic Chemistry 1999, volume 38, 2860-2867. The Cd(OH)2 structure is a recurring motif in inorganic chemistry. For example it is adopted by vanadium ditelluride.
Preparation, and reactions Cadmium hydroxide is produced by treating an aqueous solution containing Cd2+ (say cadmium nitrate) with sodium hydroxide: Cd(NO3)2 + 2 NaOH → Cd(OH)2 + 2 NaNO3
Cd(OH)2 and cadmium oxide exhibit similar reactions. Cadmium hydroxide is more basic than zinc hydroxide. It forms the anionic complex [Cd(OH)4]2− when treated with concentrated base. It forms complexes with cyanide, thiocyanate, and ammonia.
Cadmium hydroxide loses water on heating, producing cadmium oxide. Decomposition commences at 130 °C and is complete at 300 °C. Reactions with mineral acids (HX) gives the corresponding cadmium salts (CdX2). With hydrochloric acid, sulfuric acid, and nitric acid, the products are cadmium chloride, cadmium sulfate, and cadmium nitrate, respectively.
Uses It is generated in storage battery anodes, in nickel-cadmium and silver-cadmium storage batteries in its discharge: 2 NiO(OH) + 2 H2O + Cd → Cd(OH)2 + 2 Ni(OH)2
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