Thermodynamics of the dissociation of the pyridinium ion

Abstract

The pK of the pyridinium ion at ionic strength 10^-4 has been measured spectrophotometrically at ten temperatures in the range 5-50°. At 25° the enthalpy of dissociation, ΔH⁰, is 4.28±0.04 kcal mole^-1; and the entropy of dissociation, ΔS⁰, is -9.6±0.13 cal deg^-1 mole^-1.