We report the interfacial tensions between carbon dioxide and CaCl2(aq), MgCl2(aq), and Na2SO4(aq) with molalities from (0.49 to 5.0) mol.kg(-1). The measurements were made at temperatures between (323 and 423) K at various pressures up to 50 MPa. The pendant-drop method was implemented in a high-pressure view cell filled with water-saturated CO, into which single drops of brine were injected through a suitable capillary. The expanded uncertainties at 95 % confidence are 0.05 K in temperature and 70 kPa in pressure. For the interfacial tension, the expanded relative uncertainty at 95 % confidence was 1.6 %. The results of this study show that interfacial tension increases linearly with molality. Further, at constant temperature and pressure, the interfacial tension is the same function of the positive charge molality for all salts investigated in this work.