The product of the concentrations of ions present in a given solution taking the stoichiometry into account. For a sodium chloride solution the ionic product is [Na+][Cl−]; for a calcium chloride solution it is [Ca2+][Cl−]2. In pure water, there is an equilibrium with a small amount of self-ionization:H2O⇌H++OH− The equilibrium constant of this dissociation is given by KW=[H+][OH−] since the concentration [H2O] can be taken as constant. KW is referred to as the ionic product of water. It has the value 10−14 mol2 dm−6 at 25°C. In pure water (i.e. no added acid or added alkali) [H+]=[OH−]=10−7 mol dm−3. In this type of self-ionization of a solvent the ionic product is also called the autoprotolysis constant. See also solubility product; pH scale.