Congo Red Solution, Sodium Salt Of Benzidinediazo-Bis-1-Naphthylamine-4-Sulfonic Acid.
Congo Red is an acid-base indicator and it turns red when it comes in contact with bases or alkalies and turns blue in presence of acids.Congo red is water-soluble compound and its solubility is greater in organic solvents. Congo Red is a heterocyclic aromatic chemical compound with molecular formula, C32H22N6Na2O6S2
Mol. weight: 696.665 g/mol
Odor: Odorless.
Color: Red. Brownish-red. (Dark.)
pH (1% soln/water): 8.5 - 9.0 [Basic.]
Melting Point: >360°C (680°F)
Solubility: Soluble in cold water. Very slightly soluble in acetone. Insoluble in diethyl ether. Soluble in Ethanol. Solubility in water: 1g/30 ml water
Congo red was formerly used to dye cotton but has been superseded by dyes more resistant to light and to washing. It is still used in histology to stain tissues for microscopic examination, and to serve as an acid-base indicator, since it turns red in the presence of alkalies and blue when exposed to acids.
Congo Red is an inverse ph indicator.
