An insoluble organic polymer containing Cation groups that attract and hold anions present in a surrounding solution in exchange for anionspreviously held. Anion resins may be either strongly or weakly basic. Strongly basic anion resins maintain their positive charge across a wide pH range, whereas weakly basic anion resins are neutralized at higher pH levels. Weakly basic resins do not maintain their charge at a high pH because they undergo deprotonation. They do, however, offer excellent mechanical and chemical stability.