Neutralisation indicators in 2-methylpropan-2-ol: their pKa values and chromatic parameters of transition ranges

Abstract

A series of commercial indicators in 2-methylpropan-2-ol has been established that covers the whole useful pH range. The dissociation equilibria of these indicators obey three different models, and the effect of ionic strength has been considered for each one. The chromaticity coordinates, pK_a values, transition pH range, pH of maximum colour change, optimum concentration for the titration and quality of colour change have been determined. A variety of acids and their mixtures have been titrated in order to test the practical usefulness of the indicators.