In substitution reactions, one atom or radical replaces another. The most common type of substitution reactions of compounds of metals is ion exchange accompanied by precipitation. The most common substitution reactions of compounds of non-metallic elements are nucleophilic and electrophilic substitution.

Ion substitution reactions abound in geology in processes like sedimentation, mineral formation, and the development of underground caverns with exotically shaped stalactites and stalagmites. In the human body, the products of ion substitution reactions form bones and teeth. Chemists have applied ion substitution reactions to numerous tasks, ranging from the preparation of commercial products such as baking soda to the removal of undesirable metal ions from drinking water and the recycling of metal ions dissolved in waste water.

A quantitative description of the substitution chemistry of minerals and salts, requires a more precise definition of the term solubility. When a material dissolves in a liquid...