1. Chemistry A chemical compound formed by the neutralization of an acid with a base. For example, H2SO4 (acid) + 2NaOH (base) = Na2SO4 (salt) + 2H2O (water). 2. Water Treatment Sodium chloride (NaCl) or potassium chloride (KCl), both of which are used in solution during the regeneration of cation exchange water softeners and some dealkalizers. 3. Common table salt, which is sodium chloride (NaCl).