Low temperature phase relations in the ice-stable field of the system NaCl-CaCl₂-H₂O were determined under 1 atm. total pressure along the NaCl-H₂O and CaCl₂-H₂O binaries and along five pseudobinaries with constant NaCl/(NaCl+CaCl₂) weight ratios. The results are in excellent agreement with published data along the NaCl-H₂O binary but show large discrepancies when compared to previous determinations of the ice liquidus along the CaCl₂-H₂O binary and in the NaCl-CaCl₂-H₂O ternary. At moderate to high salinities, isotherms cross the ice sub-field at lower total salt concentrations than previously reported. In addition, NaCl/(NaCl+CaCl₂) weight ratios estimated from hydrohalite- and ice-melting temperatures may be low by as much as 15%.
Relative densities were measured for NaCl(aq) and CaCl₂(aq) solutions to 250°C and 400 bars and over the range of ionic strengths 0.2 - 5.5 and 0.2 - 19.2 mol·kg⁻¹, respectively. The results span the pressure and temperature of earlier volumetric studies and extend to higher molalities than reported previously. The relative densities have been fitted as apparent molar volumes (V<sub>Φ</sub>) using the Pitzer ion-interaction treatment, with appropriate expressions chosen for the temperature- and pressure-dependence of the virial coefficients of the model. The results presented for NaCl(aq) are in good agreement with published results to 250°C. The results presented for CaCl₂(aq) are in good agreement with published values to approximately 125°C. Above 125°C the inter- and intralaboratory precision of the published data deteriorate and are often in very poor agreement with the data from this Study. The representation for V<sub>Φ</sub> for CaCl₂(aq) was integrated with respect to pressure to establish the pressure dependence of excess free energies over the temperature range studied. CaCl₂ activity coefficients (γ±) have been derived to 250°C, 400 bars and 4 mol·kg⁻¹ using published fits of CaCl₂ activity coefficient data along the vapor saturation surface and the pressure dependence determined in this work. The volumetric data indicate that the mean ionic activity coefficient, γ±(CaCl₂), increases by a maximum of 32% at 400 bars, 250°C, and 4 mol·kg⁻¹ as compared with its value at saturation pressure.
Relative densities were also measured for several ternary { NaCl+CaCl₂}(aq) solutions at 25 and 35°C and 1 atm. These results substantially expand the volumetric data base for ternary solutions. Based on the results of this study most of the previously reported 308.15 K density data in the ternary appear to contain large errors. / Ph. D.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/39729 |
| Date | 10 October 2005 |
| Creators | Oakes, Charles Steger |
| Contributors | Geological Sciences, Bodnar, Robert J., Simonson, John M., Hewitt, David A., Tracy, Robert J., Rimstidt, J. Donald |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Language | English |
| Detected Language | English |
| Type | Dissertation, Text |
| Format | xii, 120 leaves, BTD, application/pdf, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
| Relation | OCLC# 29179395, LD5655.V856_1992.O243.pdf |
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