Water's hardness is determined by the concentration of multivalent cations in the water. Multivalent cations are positively charged metal complexes with a charge greater than 1+. Usually, the cations have the charge of 2+. Common cations found in hard water include Ca2+ and Mg2+. The reduction of water hardness in laundry applications and the dissolution of scale in boilers both rely on EDTA and related complexantsto bind Ca2+, Mg2+, as well as other metal ions