Congo red
Congo red
noun \ˌkäŋ-(ˌ)gō-ˈred\Definition of CONGO RED
: 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
