noun Chemistry.
any of a class of sulfur-containing compounds having the type formula RSH, in which R represents a radical, and having an extremely offensive, garlicky odor.

1825–35; < Latin, short for phrase corpus mercurium captāns body capturing quicksilver Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2014.
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World English Dictionary
mercaptan (mɜːˈkæptæn)
another name (not in technical usage) for thiol
[C19: from German, from Medieval Latin mercurium captans, literally: seizing quicksilver]

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American Heritage
Medical Dictionary

mercaptan mer·cap·tan (mər-kāp'tān')
Any of a class of organic compounds in which the oxygen of an alcohol has been replaced by sulfur and which have distinctive, often disagreeable, odors. Also called thiol.

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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American Heritage
Science Dictionary
mercaptan   (mər-kāp'tān')  Pronunciation Key 
See thiol.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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Encyclopedia Britannica


any of a class of organic chemical compounds similar to the alcohols and phenols but containing a sulfur atom in place of the oxygen atom. Thiols are among the odorous principles in the scent of skunks and of freshly chopped onions; their presence in petroleum and natural gas is objectionable because they have disagreeable odours, interfere with catalysts used in refining processes, and produce sulfur dioxide upon combustion.

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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Example sentences
Mercaptan is an irritant that can cause respiratory problems, headaches, nausea and vomiting.
The intense heat also buckled the rail beneath the methyl mercaptan tank car.
Acute and subchronic toxicity studies of rats exposed to vapors of methyl mercaptan and other reduced sulfur compounds.
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