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Medical Term:

cation exchange

Pronunciation: kat′ī-on eks-chānj′

Definition: The process by which a cation in a liquid phase exchanges with another cation present as the counter ion of a negatively charged solid polymer (cation exchanger). A cation-exchange reaction in removal of the Na+ of a sodium chloride solution is RSO3−H+ + Na+ → RSO3−Na+ + H+ (R is the polymer, RSO3− is the cation exchanger); if this is combined with the anion-exchange reaction, NaCl is removed from the solution (desalting). Cation exchange may also be used chromatographically, to separate cations, and medicinally, to remove a cation, H+, from gastric contents, or Na+ and K+ in the intestine.

See: anion exchange