Methyl red is a dark red crystalline powder. Methyl red is a pH indicator; it is red in pH under 4.4, yellow in pH over 6.2, and orange in between, with a pKa of 5.1.
Methyl Red is a maroon red crystal azo dye.Methyl Red is a pH indicator and changes color at a pH of 5.5.It Is consisting of benzoic acid substituted at position 2 by a 4-[(dimethylamino)phenyl]diazenyl group.