Interfacial tension of (Brines + CO 2): (0.864 NaCl + 0.136 KCl) at temperatures between (298 and 448) K, pressures between (2 and 50) MPa, and total molalities of (1 to 5) mol·kg -1

We report the interfacial tension between carbon dioxide and aqueous solutions of the mixed salt system (0.864 NaCl + 0.136 KCl) with total salt molalities between (0.98 and 4.95) mol·kg -1. The measurements were made at temperatures between (298 and 473) K at various pressures up to 50 MPa by means of imaging a pendant drop of CO 2-saturated brine surrounded by a water-saturated CO 2 phase. The expanded uncertainties at 95 % confidence are 0.05 K in temperature, 70 kPa in pressure, and for interfacial tension γ, the larger of 0.016γ and 0.6 mN·m -1. The results of the study indicate that the interfacial tension increases linearly with the molality of the salt solution. An empirical equation has been developed to represent the present results as a function of temperature, pressure, and molality with an expanded uncertainty of 1.6 mN·m -1.