The effect of pressure on complex ion equilibria

Abstract

The effect of pressure on the formation of complex ions in solutions of cobaltous chloride and in solutions containing iodine and iodide has been shown to be in qualitative agreement with a theory (Buchanan and Hamann 1953) attributing these effects primarily to changes in the free energy of salvation of the ions. The dissociation constant of tri-iodide ions in water at 22 °C has been shown to decrease from 1.6 x 10^-3 mol kg^-1 at atmospheric pressure to 1.2 x mol kg^-1 at 1500 atm. The enthalpy of dissociation of the tri-iodide ion was found to be approximately -5 kcal mol^-1 and to be little affected by a pressure of 1500 atm.