Viscosities, densities, apparent and partial molar volumes of concentrated aqueous MgSO4solutions at high temperatures and high pressures

Density of two (2.224 and 2.535 mol kg−1) and viscosity of eight (0.085, 0.255, 0.437, 0.722, 0.923, 1.824, 2.291, and 2.623 mol kg−1) binary aqueous MgSO4 solutions have been measured with a constant-volume piezometer immersed in a precision liquid thermostat and a capillary flow technique, respectively. Measurements were made at pressures up to 30 MPa. The range of temperature was 288 to 398 K for the density measurements and 298–448 K for the viscosity measurements. The total uncertainty of density, viscosity, pressure, temperature, and composition measurements were estimated to be <0.06%, 1.6%, 0.05%, 15 mK, and 0.02%, respectively. The effect of temperature, pressure, and concentration on density and viscosity of binary aqueous MgSO4 solutions were studied. Apparent and partial molar volumes were derived using the measured values of density for the solutions. The viscosity data have been interpreted in terms of the extended Jones–Dole equation for strong electrolytes to accurately calculate the viscosity A- and B-coefficients as a function of temperature. The derived values of the viscosity A- and B-coefficients were compared with the results predicted by Falkenhagen–Dole theory of electrolyte solutions and calculated using the ionic B ±-coefficient data. The hydrodynamic molar volumes V k were calculated using the present experimental viscosity data.