text: Methyl yellow, or C.I. 11020, is an organic compound with the formula CHNCHN(CH).  It is an azo dye derived from dimethylaniline. It is a yellow solid.  According to X-ray crystallography, the CN core of the molecule is planar.
  It is used as a dye for plastics and may be used as a pH indicator.  In aqueous solution at low pH, methyl yellow appears red. Between pH 2.9 and 4.0, methyl yellow undergoes a transition, to become yellow above pH 4.0.