Cadmium hydroxide
# Cadmium hydroxide

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.

## Structure, preparation, and reactions

Cadmium hydroxide adopts the same structure as $Mg(OH)_2,$ consisting of slabs of octahedral metal centers surrounded by octahedral of hydroxide ligands.

It is produced by treating cadmium nitrate with sodium hydroxide:

    $Cd(NO_3)_2$ + 2 NaOH → $Cd(OH)_2$ + 2 $NaNO_3$

Preparation has been achieved from some other cadmium salts,

$Cd(OH)_2$ and cadmium oxide react equivalently. 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) produce the corresponding cadmium salts $(CdX_2).$ 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 $H_2O$ + Cd → $Cd(OH)_2$ + 2 $Ni(OH)_2$
