a water-soluble powder, C32H22O6N6S2Na2, one of the Congo colors that is not acid-fast or lightfast: used chiefly as a dye, biological stain, and chemical indicator.
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Origin of Congo red
First recorded in 1880–85
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
a brownish-red soluble powder, used as a dye, a diagnostic indicator, a biological stain, and a chemical indicator. Formula: C 32 H 22 N 6 O 6 S 2 Na 2
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
An acid dye used as an indicator in testing for free hydrochloric acid in gastric contents, as a laboratory aid in the diagnosis of amyloidosis, and as a histologic stain for amyloid.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.