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We report the densities of MgCl2(aq), CaCl2(aq), KI(aq), NaCl(aq), KCl(aq), AlCl3(aq), and the mixed salt system (1 – x)NaCl + xKCl(aq), where x denotes the mole fraction of KCl, at temperatures between (283 and 472) K and pressures up to 68.5 MPa. The molalities at which the solutions were studied were (1.00, 3.00, and 5.00) mol·kg–1 for MgCl2(aq), (1.00, 3.00, and 6.00) mol·kg–1 for CaCl2(aq), (0.67, 0.90, and 1.06) mol·kg–1 for KI(aq), (1.06, 3.16, and 6.00) mol·kg–1 for NaCl(aq), (1.06, 3.15, and 4.49) mol·kg–1 for KCl(aq), (1.00 and 2.00) mol·kg–1 for AlCl3(aq), and (1.05, 1.98, 3.15, and 4.95) mol·kg–1 for (1 – x)NaCl + xKCl(aq), with x = 0.136. The measurements were performed with a vibrating-tube densimeter calibrated under vacuum and with pure water over the full ranges of pressure and temperature investigated. An analysis of uncertainties shows that the relative uncertainty of density varies from 0.03 % to 0.05 % depending upon the salt and the molality of the solution. An empirical correlation is reported that represents the density for each brine system as a function of temperature, pressure, and molality with absolute average relative deviations of approximately 0.02 %. Comparing the model with a large database of results from the literature, we find absolute average relative deviations of 0.03 %, 0.06 %, 0.04 %, 0.02 %, and 0.02 % for the systems MgCl2(aq), CaCl2(aq), KI(aq), NaCl(aq), and KCl(aq), respectively. The model can be used to calculate density, apparent molar volume, and isothermal compressibility over the full ranges of temperature, pressure, and molality studied in this work. An ideal mixing rule for the density of a mixed electrolyte solution was tested against our mixed salt data and was found to offer good predictions at all conditions studied with an absolute average relative deviation of 0.05 %.
Ghafri et al. (Tue,) studied this question.