Effect of pressure on ionization of triethylamine in methanol

Abstract

The ionic dissociation constans of ionization of triethylamine in methanol were determined from the measurements of electrical conductivities over the range of 1-2000kg cm^-2 at 25℃ and 1-1600kg cm^-2 at 30 and 40℃. The ionization constants were obtained by the Shedlovsky equation which contains the equivalent conductivity of weak electrolyte and the limiting equivalent conductivity of strong electrolyte. The data were treated by the Fuoss-Onsager equation for potassium chloride, triethylammonium chloride, and potassium methoxide to determine the limiting equivalent conductivities after the justification of the Onsager limiting equation at high pressure. The ionic dissociation constant at 25℃ increased from 0.502×10^-6 mol kg^-1 at 1 atm to 5.78×10^-6 mol kg^-1 at 2000kg cm^-2, and decreased with temperature to 0.264×10^-6 mol kg^-1 at 1 atm and 40℃. The pressure dependence of ionization constant was quantitatively explained by the change of dielectric constant with pressure, and the electrostrictive volume change, and the other volume changes (crystal, void volume change et al.) at 1 atm. It was found that both the electrostrictive volume change and the other volume changes play an important role for the pressure effects on the ionization in methanol.