The removal of all ionized minerals and salts from a solution by a two-phase ion exchange process. First, positively charged ions are removed by a cation exchange resin in exchange for a chemically equivalent amount of hydrogen ions. Second, negatively charged ions are removed by an anion exchange resin for a chemically equivalent amount of hydroxide ions. The hydrogen and hydroxide ions introduced in this process unite to form water molecules. The term, commonly abbreviated as DI, is often used interchangeably with demineralization.