Precipitation Reaction
A reaction in which two solutions combine to form an insoluble solid that separates from the mixture.
Formula / equation
A⁺(aq) + B⁻(aq) → AB(s)
Unit
Dimensionless
In depth
Precipitation occurs when the ionic product of the two ions exceeds the solubility product of the resulting compound. It is the basis of gravimetric analysis, of qualitative tests for ions, and of industrial water softening and effluent treatment.
Examples in the real world
Adding barium chloride to a sulfate solution gives a dense white BaSO₄ precipitate — the standard sulfate test.