methyl yellow

Methyl yellow, also known as oil yellow 1b, is a chemical compound used as a chemical indicator. It is an acid-base indicator that changes color based on the acidity or alkalinity of a solution.1

Methyl yellow imparts a yellow color to alkaline solutions. When acid is added, the solution remains yellow until all the alkali is neutralized, at which point the color abruptly shifts to red. This color change is visible even at very low concentrations, as low as a few parts per million, and does not affect the solution's conditions. Methyl yellow is yellow if the hydrogen ion concentration is less than 0.0001 mole per liter and red if it exceeds this amount. Its primary application is in detecting the end points of titrations.1