• synonyms


[naf-thawl, -thol, nap-]
noun Chemistry.
  1. either of two isomeric hydroxyl derivatives, C10H7OH, of naphthalene (alpha-naphthol or 1-naphthol and beta-naphthol or 2-naphthol), white or yellowish crystals, with a phenolic odor, that darken on exposure to light: used chiefly in dyes, drugs, perfumes, and insecticides.
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Origin of naphthol

First recorded in 1840–50; naphth- + -ol1
Also called hydroxynaphthalene.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for naphthol

Historical Examples of naphthol

  • Various additions have been made from time to time to the naphthol bath.

    The Dyeing of Cotton Fabrics

    Franklin Beech

  • When a good method for making the naphthol was discovered in 1869, the dye was made from this.


    Raphael Meldola

  • Both the formaldehyde and the naphthol exercise tanning actions, but the process is not used in practise.

  • The compounds formed are brilliant orange dyes, the latter being still largely consumed as “naphthol orange.”


    Raphael Meldola

  • When this compound is combined with naphthol diazo-azo dyes are produced.

British Dictionary definitions for naphthol


  1. a white crystalline solid having two isomeric forms, alpha-naphthol, used in dyes, and beta-naphthol, used in dyes and as an antioxidant. Formula: C 10 H 7 OH
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Word Origin for naphthol

C19: from naphtha + -ol 1
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

naphthol in Medicine


(năfthôl′, -thōl′, năp-)
  1. An organic compound occurring in two isomeric forms, alpha-naphthol and beta-naphthol.naphthalenol
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The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

naphthol in Science


[năfthôl′, -thōl′, năp-]
  1. A poisonous organic compound occurring in two isomeric forms. Both isomers are important in the manufacture of dyes, and also in making antiseptics, insecticides, and tanning agents. Naphthol consists of a hydroxyl group (OH) attached to naphthalene. Chemical formula: C10H8O.
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The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.