It is employed as an electrophoresis tracking dye and also finds its uses as an industrial dye, a laboratory acid-base indicator and a biological stainto detect proteins and nucleic acids (absorbance at 610 nm), particularly when staining living tissues. In gel electrophoresis it can be used as a color marker and asa biological stain it can be used to stain proteins and nucleic acids. Bromophenol blue is an intermediate and is used as an acid-based indicator in the pH range of 3-4.6 where the color changes from yellow to blue.