Search Result for "congo red":
Wordnet 3.0

NOUN (1)

1. a red-brown azo dye especially as a chemical pH indicator (congo red is red in basic and blue in acidic solutions); 



The Collaborative International Dictionary of English v.0.48:

Congo red \Congo red\ (Chem.)
   An artificial red dye from which the Congo group received its
   name. It is also widely used either in aqueous solution or as
   test paper (

   Congo paper) for the detection of free acid, which turns it
      blue.
      [Webster 1913 Suppl.]


WordNet (r) 3.0 (2006):

congo red
    n 1: a red-brown azo dye especially as a chemical pH indicator
         (congo red is red in basic and blue in acidic solutions)