- a water-soluble powder, C32H22O6N6S2Na2, one of the Congo colors that is not acid-fast or lightfast: used chiefly as a dye, biological stain, and chemical indicator.
Origin of Congo red
First recorded in 1880–85
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
- a brownish-red soluble powder, used as a dye, a diagnostic indicator, a biological stain, and a chemical indicator. Formula: C 32 H 22 N 6 O 6 S 2 Na 2
- An acid dye used as an indicator in testing for free hydrochloric acid in gastric contents, as a laboratory aid in the diagnosis of amyloidosis, and as a histologic stain for amyloid.