congo red
NounOpen English WordNet
Noun (1)
- a red-brown azo dye especially as a chemical pH indicator (congo red is red in basic and blue in acidic solutions)Type of azo dye, acid-base indicator
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Webster's Dictionary (1913)
Congo red.
Chemistry 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’s Revised Unabridged Dictionary (1913), from GCIDE 0.54 · with additions: 1913 supplement