Heat capacity and other thermodynamic properties of Na sub 2 SO sub 4 (aq) in hydrothermal solutions and the solubilities of sodium sulfate minerals in the system Na-Cl-SO sub 4 -OH-H sub 2 O to 300 degree C
- Univ. of California, Berkeley (USA)
Heat capacities of Na{sub 2}SO{sub 4}(aq) solutions have been measured from 140{degree}-300{degree}C at 200 bars using a flow-calorimeter over the molality range of 0.05-1.5 mol{center dot}kg{sup minus 1}. Using the ion-interaction or virial coefficient approach developed by Pitzer (1973, 1979, 1987) and coworkers, and approximating the pressure-dependencies of the various Na{sub 2}SO{sub 4}(aq) thermodynamic quantities with those of NaCl(aq) calculated from the equations of Rogers and Pitzer (1982), the authors measured heat capacities were combined with literature values on heat capacities, enthalpies, and osmotic coefficients at temperatures to 225{degree}C and at pressures mostly at 1 bar or vapor-saturation pressure to yield a comprehensive set of equations for the thermodynamic properties of Na{sub 2}SO{sub 4}(aq) at temperatures 25{degree}-300{degree}C, pressure to at least 200 bars, and molalities to 3.0 mol{center dot}kg{sup minus 1}. Good agreement between experimental and predicted solubilities in water indicate that the ion-interaction model can be used successfully to predict mineral-solution equilibria to 300{degree}C without an explicit accounting for ion-pairs, and demonstrates that heat capacity measurements can be used to obtain reliable high-temperature and high-pressure activity properties of electrolyte solutions. The binary and ternary mixing parameters {theta}{sub ij} and {psi}{sub ijk} are required by the ion-interaction model for calculations for multicomponent mixtures. It was found sufficient to adopt previously determined values for {theta}{sub ij} at 25{degree}C without temperature dependence and, from the solubility data, to determine temperature-dependent {psi}{sub ijk} functions.
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 5204260
- Journal Information:
- Geochimica et Cosmochimica Acta; (USA), Journal Name: Geochimica et Cosmochimica Acta; (USA) Vol. 52:10; ISSN GCACA; ISSN 0016-7037
- Country of Publication:
- United States
- Language:
- English
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58 GEOSCIENCES
580000 -- Geosciences
ALKALI METAL COMPOUNDS
CHEMICAL COMPOSITION
CHEMISTRY
DIFFUSION
DISPERSIONS
DISSOLUTION
ELECTROLYTES
ENERGY SYSTEMS
ENTHALPY
GEOCHEMISTRY
GEOTHERMAL SYSTEMS
HYDROTHERMAL SYSTEMS
MINERALS
MIXTURES
OSMOSIS
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
SODIUM COMPOUNDS
SODIUM SULFATES
SOLUBILITY
SOLUTIONS
SPECIFIC HEAT
SULFATE MINERALS
SULFATES
SULFUR COMPOUNDS
TEMPERATURE EFFECTS
THERMAL WATERS
THERMODYNAMIC ACTIVITY
THERMODYNAMIC PROPERTIES