EXPERIMENTAL-STUDY OF DISSOCIATION OF HCL FROM 350-DEGREES-C TO 500-DEGREES-C AND FROM 500 TO 2500 BARS - THERMODYNAMIC PROPERTIES OF HCL(AQ)DEGREES

New values of the dissociation constants of HCl degrees referring to l ow density supercritical solutions and near-critical temperatures of w ater (350-500 degrees C and 500-2500 bars) have been obtained based on comparison of AgCl(s) solubility in NaCl or KCl solutions with Ag-(s) solubility in HCl + NaCl or KCl solutions at controlled hydrogen fuga cities. During the course of this study the thermodynamic properties o f AgCls- were refined with the aid of the revised HKF equation of stat e (Tanger and Helgeson, 1988). The dissociation constants of HCl degre es obtained in the present work are higher than that found from electr ical conductance measurements (Frantz and Marshall, 1984) by more than an order of magnitude at pressures of about 500 bars, but the differe nce becomes smaller as the pressure increases. Both sets of dissociati on constants agree well at high pressures where the isothermal compres sibility of water is less than about 1.42.10(-4) bar(-1). To reliably compare experimental data obtained by different methods, the Redlikh-K wong equation of state was applied to available literature data as wel l as to the results of this study. Finally, the standard state thermod ynamic properties and HKF parameters for HCl degrees((aq)) were establ ished. These results allow extrapolation of the thermodynamic properti es of HCl degrees((aq)) and consequently the HCl dissociation constant up to 700 degrees C and 5000 bars. Copyright (C) 1997 Elsevier Scienc e Ltd.