Congo red

noun

Con·​go red ˈkäŋ-(ˌ)gō- 

: an azo dye C₃₂H₂₂N₆Na₂O₆S₂ that is red in alkaline and blue in acid solution and that is used especially as an indicator and as a biological stain

Word History

Etymology

Congo, territory in Africa

First Known Use

1885, in the meaning defined above

Kids Definition

Congo red

noun

Con·​go red ˌkäŋ-ˌgō- 

: a dye that is red in alkaline and blue in acid solution

Etymology

named for Congo, territory in Africa

Medical Definition

Congo red

noun

ˌkäŋ-(ˌ)gō-ˈred 

: an azo dye C₃₂H₂₂N₆Na₂O₆S₂ that is red in alkaline and blue in acid solution and that is used in a number of diagnostic tests and especially for the detection of amyloidosis since the injected dye tends to be retained by abnormal amyloid deposits