The System Water—Carbon Dioxide—Sodium Chloride to 773 K and 300 MPa

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Abstract
Experimental results are reported for fluid‐fluid phase equilibria of the ternary system H2OCO2NaCl. Measurements were extended to 773 K and pressures to 300 MPa. A “synthetic” method was used: Known quantities of the three components were filled into an autoclave at room temperature. The autoclave with a sapphire window and variable volume is described. Transition points to homogeneous one‐phase conditions could be determined from recordedp—T‐curves at constant volumes and from visual observation. From the transition pointsp—T‐curves on the three‐dimensional phase equilibrium boundary surface at constant compositions, “isopleths”, were obtained. Data for 20 isopleths with CO2‐concentrations between 0.2 and 85 mol% and with 6 weight YO of NaCl are presented together with a few additional results for higher salt concentrations. Molar volumes were measured at the phase boundary surface and within the one‐phase region. Excess molar volumes are given. In comparison with the binary H2O‐CO2system, the addition of NaCl shifts the range of partial immiscibility to higher temperatures by up to 100 K; for example from 573 to 673 K at 100 MPa for 48 mol% CO2. Results are in agreement with earlier data of Takenouchi and Kennedy. Considerations of the ternary phase diagram H2OCO2NaCl within a wide range of conditions are given.