Acid-base Behaviour of Some Indicators in Mixed Solvents

The pK's of indicators, methyl orange. bromocresol green and thymol blue have been determined spectrophotometrically in dioxane-watm and methanol-water media. The change in pK's when the organic component is added to water has been analysed in terms of the property of the medium (basicity and aloso ion-solvent interaction) using Hepler equation for calculating the electrostatic contributions.