- a halogen element, a heavy, greenish-yellow, incombustible, water-soluble, poisonous gas that is highly irritating to the respiratory organs, obtained chiefly by electrolysis of sodium chloride brine: used for water purification, in the making of bleaching powder, and in the manufacture both of chemicals that do not contain chlorine, as ethylene glycol, and of those that do. Symbol: Cl; atomic weight: 35.453; atomic number: 17.
- a toxic pungent greenish-yellow gas of the halogen group; the 15th most abundant element in the earth's crust, occurring only in the combined state, mainly in common salt: used in the manufacture of many organic chemicals, in water purification, and as a disinfectant and bleaching agent. Symbol: Cl; atomic no: 17; atomic wt: 35.4527; valency: 1, 3, 5, or 7; density: 3.214 kg/m³; relative density: 1.56; melting pt: –101.03°C; boiling pt: –33.9°C
