The behaviour and properties of some acid-base indicators: a review

Abstract

This review focuses on Seven Acid-Base Indicators from the azo class and from the second type: Methyl Orange; Methyl Red; Methyl Yellow; Alizarin Yellow R; Alizarin Yellow GG; Tropaeolin O and Magneson I. These indicators show different colors involving the chemical reaction in aqueous solutions as results as change the acidity of solution causing the formation two different structure forms one in acid form and another in basic forms with possibility formation of resonance structures. Different variables such as temperature; ionic strength; solvents; concentrations; pressure; substituent’s; position of function group and surfactant  that influence on the behavior of Acid-Base indicators were explained. The electronic absorption spectral, equilibrium, terminological aspects and characteristics as well as the possible schemes of formation two compounds at isosbestic point are discussed. The contributions of different methods using to estimate the dissociation constant for it is discussed.