Thermodynamics of proton dissociation of acridinium ion in aqueous solution

Abstract

Standard thermodynamic function changes (ΔG θ°, ΔH θ o , ΔS θ o and ΔC pθ o ) are reported for proton dissociation of acridinium cation in aqueous solution. These values have been determined from a series of precise and accurate acid equilibrium constants, K a. The equilibrium constants have been obtained spectrophotometrically over a range of temperatures from 2 to 66°C at several ionic strengths ( I = 0.005, 0.007, 0.01, 0.05 and 0.25 M). Although the ionic strength does not affect in general the Gibbs free-energy values, the results suggest a possible influence on entropy and enthalpy changes.