Pyrocatechol Violet is a complexometric indicator dye. This phthalein dye chelates metals to form blue to blue-violet complexs. It is also a pH indicator with a transition interval from 0 - 8 (red to violet). It is known to be unstable when alkaline. The stability is improved at a neutral pH. When the pH is between 2-7 the color may be yellow.A complexometric indicator. Pyrocatechol Violet is a complexometric indicator dye. This phthalein dye chelates metals to form blue to blue-violet complexs. It is also a pH indicator with a transition interval from 0 - 8 (red to violet). It is known to be unstable when alkaline. The stability is improved at a neutral pH. When the pH is between 2-7 the color may be yellow. A complexometric indicator.