congo red

2 definitions found

congo red - 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.]

congo red - WordNet (r) 2.1 (2005) :

  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)