Methyl Orange
An acid–base indicator that is red in acid and yellow in alkali, changing between pH 3.1 and 4.4.
Formula / equation
C₁₄H₁₄N₃NaO₃S
Unit
Dimensionless
In depth
Its low transition range suits titrations of a weak base with a strong acid, where the equivalence point is acidic. It is an azo dye whose colour change results from protonation of an azo nitrogen, which alters the conjugated system.
Examples in the real world
Titrating sodium carbonate with hydrochloric acid to the second equivalence point.