Electrical conductivities of aqueous solutions of KCl, KOH and HCl, and the ionization of water at high shock pressures

Abstract

Measurements have been made of the electrical conductivities of aqueous solutions of KCl, KOH and HCl at shock wave pressures in the range 70–133 kbar. The molar conductivity of KCl was not measurably different from its normal value, and this finding is interpreted as meaning that although the temperature jump in the shock front tends to increase the mobilities of K⁺ and Cl^– ions, the simultaneous jump in density has an opposite and cancelling effect. On the other hand, the conductivities of HCl and KOH increased several fold, indicating that the excess mobilities of hydrogen ions and hydroxyl ions increase by a factor of 3-6 under the shock conditions.

By combining the measured ionic conductivities with earlier measurements of the conductivity of pure water it has been estimated that the ionization product K_w of water increases to about 0.09 mol² kg^–2 at a shock pressure af 133 kbar. It is suggested that the ionization of water into H₃O⁺ and OH^– ions becomes nearly complete at 200 kbar and that this transformation may be responsible for the difference in the pressure-volume behaviour of shocked water below and above the 150–200 kbar region.