Salt metathesis reaction

A salt metathesis reaction (also called a double displacement reaction, double replacement reaction, or double decomposition) is a type of chemical reaction in which two compounds exchange their component ions to form two new compounds. Often, one of the products precipitates. Furthermore one of the reactants is typically a salt.

AB + CD -> AD + CB

In older literature, the term double decomposition is common. The term double decomposition is more specifically used when at least one of the substances does not dissolve in the solvent, as the ligand or ion exchange takes place in the solid state of the reactant. For example:

AX(aq) + BY(s) → AY(aq) + BX(s).