chlo·rine (klôr??n?, -?n)n. Symbol Cl A highly irritating, greenish-yellow halogen element, existing as a diatomic gas, Cl2, and capable of combining with nearly all other elements, produced principally by electrolysis of sodium chloride and used widely to disinfect water, as a bleaching agent, and in the manufacture of many important compounds including chlorates, sodium hypochlorite, and chloroform. Atomic number 17; atomic weight 35.453; freezing point -100.5°C; boiling point -34.04°C; specific gravity 1.56 (-33.6°C); valence 1, 3, 5, 7. See Periodic Table.American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.chlorine (?kl??ri?n) or chlorinn (Elements & Compounds) 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[C19 (coined by Sir Humphrey Davy): from chloro- + -ine2, referring to its colour]Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014chlo?rine (?kl?r in, -?n, ?klo?r-) n. a halogen element, a heavy, greenish yellow poisonous gas: used to purify water and to make bleaching powder and various chemicals. Symbol: Cl; at. wt.: 35.453; at. no.: 17. [1810;