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

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

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

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

The chemical reaction of cheese is normally acid to phenolphthalein, although there is generally no free acid, as shown by Congo red, the lactic acid being converted into salts as fast as formed.

From Outlines of Dairy Bacteriology, 8th edition A Concise Manual for the Use of Students in Dairying by Russell, H. L. (Harry Luman)