The use of 2,6-dichlorophenolindophenol as indicator in acid-base titrations

2,6-Dichlorophenolindophenol shows acid-base indicator properties. Its colour is red in acidicmedia and blue in alkaline media. 'Ihe transitional pH value is 5.7 and the colour change is sharp and easy to observe. The use of the indicator in various acid-base titrations, as well as the effects of neutral salts, alcohol and temperatures, were checked. The absorption spectra of the acidic and basic forms of the indicator are presented.