Chlorine

Webster's Dictionary of the English Language

·noun One of the elementary substances, commonly isolated as a greenish yellow gas, two and one half times as heavy as air, of an intensely disagreeable suffocating odor, and exceedingly poisonous. It is abundant in nature, the most important compound being common salt. It is powerful oxidizing, bleaching, and disinfecting agent. Symbol Cl. Atomic weight, 35.4.