Effect of pressure on ionization equilibria in water at 25°C

Abstract

A simpler equation than that proposed by Owen and Brinkley in 1941 is shown to be satisfactory for the calculation of the pressure dependence of the dissociation constant to approximately 2000 bars, from density and compressibility measurements on solutions. As a corollary, an accurate graphical method is proposed for the evaluation of standard partial molal volume and compressibility changes on ionization at atmospheric pressure (ΔV^∘₁ and κ^∘₁), from dissociation constant against pressure data. V^∘₁ and κ^∘₁ values for a wide range of acid-base equilibria are tabulated, and an approximately linear relationship between these thermodynamic function changes is demonstrated. This observation may be useful for predicting the effect of pressure on ionization equilibria for which ΔV^∘₁ but not κ^∘₁ data are available.