[kal-uh-mel, -muhl]
noun Pharmacology.
a white, tasteless powder, Hg 2 Cl 2 , used chiefly as a purgative and fungicide.
Also called mercurous chloride.

1670–80; < Neo-Latin calomelas coined from Greek kaló(s) fair + mélas black; allegedly so called because its original preparation involved turning black powder into white Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2014.
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World English Dictionary
calomel (ˈkæləˌmɛl, -məl)
a colourless tasteless powder consisting chiefly of mercurous chloride, used medicinally, esp as a cathartic. Formula: Hg2Cl2
[C17: perhaps from New Latin calomelas (unattested), literally: beautiful black (perhaps so named because it was originally sublimed from a black mixture of mercury and mercuric chloride), from Greek kalos beautiful + melas black]

Collins English Dictionary - Complete & Unabridged 10th Edition
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Word Origin & History

1670s, "mercurous chloride," from Fr. calomel, supposedly from Gk. kalos "fair" + melas "black;" but as the powder is yellowish-white this seems difficult.
Online Etymology Dictionary, © 2010 Douglas Harper
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American Heritage
Medical Dictionary

calomel cal·o·mel (kāl'ə-měl', -məl)
A colorless, white or brown tasteless compound used as a purgative and an insecticide. Also called mercurous chloride.

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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Encyclopedia Britannica


a very heavy, soft, white, sweetish-tasting halide mineral, formed by the alteration of other mercury minerals, such as cinnabar or amalgams. Calomel is found together with native mercury, cinnabar, calcite, limonite, and clay, at Moschellandsberg, Ger.; Zimapan, Mexico; and Brewster county, Texas, U.S. For detailed physical properties, see halide mineral (table)

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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Example sentences
The voltage was measured with the indicator electrode described above and a saturated calomel reference electrode on a pH meter.
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