Color changes of acid-base indicators

Conductometric titration rests on the marked changes that occur near the titration endpoint in the relation between conductivity and the amount of titrant added (an extreme or inflection point). It is used in particular for the titration of acids with base (and vice versa) in colored and turbid solutions or solutions containing reducing and oxidizing agents (i.e., in those cases where the usual color change of acid-base indicators cannot be seen). 

Die GD-Cresol Red or 4-(2, 4 -dinitrophenylazo)-1 -naphthol Spectrophotometry 10 -10 mol r Color change of acid-base indicators... 

The alternative approach is based on coupling gas diffusion and spectrophotometric detection, through monitoring the color change of acid-base indicators such as cresol red [47], 4-(2, 4 -dini-trophenylazo)-l-naphthol-5-sulfonic acid [48], bromothymol blue(BTB) [50], or the color fading of a phenolphthalein solution [45], all of them used as acceptor solution for the collection of the permeated CO2. Several environmental applications are reported in the literature. 

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