Congo red

American  

noun

Chemistry.

1. a water-soluble powder, C 32 H 22 O 6 N 6 S 2 Na 2 , 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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Congo red British  

noun

1. 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

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Etymology

Origin of Congo red

First recorded in 1880–85

Example Sentences

See Examples For:

Congo red

The leak turned a tributary of the River Congo red and killed huge numbers of fish, which some people ate, said Environment Minister Eve Bazaiba.

From BBC ● Sep. 3, 2021

As defined by pathologists1 who document amyloids in numerous diseases, the fibrils must be deposited in body tissues and fluoresce a green–yellow colour when stained with the dye Congo red and viewed between crossed polarizers.

From Nature ● Nov. 8, 2016

Amyloid is defined pathologically by the demonstration of green birefringence on binding of the dye Congo red and biophysically by a cross-β fibre diffraction pattern. b, Models of recombinant PrP fibrils and ex vivo prions.

From Nature ● Nov. 8, 2016

A large number of the dyes prepared from coal tar are called azo colours, such for instance are the Biebrich and Croceine scarlets and oranges, Naphthol black, Congo red, etc.,

From The Dyeing of Cotton Fabrics A Practical Handbook for the Dyer and Student by Beech, Franklin

The first colouring matter of this class was the so-called Congo red, discovered in 1884, and since that time a very great number have been introduced which yield almost every variety of colour.

From Encyclopaedia Britannica, 11th Edition, Volume 8, Slice 8 "Dubner" to "Dyeing" by Various