System NaCl-H/sub 2/O: relations of vapor-liquid near the critical temperature of water and of vapor-liquid-halite from 300/sup 0/ to 500/sup 0/C
Vapor-liquid relations (P-T-x) for the system NaCl-H/sub 2/O were determined experimentally at temperatures spanning the critical temperature of water (T/sub c/), the lowest temperature in the system at which critical behavior occurs. In addition, vapor-liquid-halite P-T-x (vapor) relations were determined from 300/sup 0/ to 500/sup 0/C. Results show that at 373.0/sup 0/C, immediately below T/sub c/, the vapor side of the isothermal vapor-liquid P-x boundary has a shape quite different from that previously conceived. The NaCl content of the vapor increases with pressure in a smooth manner from the pressure of the three-phase assemblage (135 bars, 0.0029% NaCl), to a pressure just below that of the vapor pressure of pure water (0.012% NaCl at 184 bars). Above this pressure the boundary abruptly reverses and projects asymptotically to 0% NaCl in a beak-like shape at 218 bars, the vapor pressure of pure water. At 375.5/sup 0/, slightly above T/sub c/, the asymptote disappears, and is replaced by a rounded nose. At progressively higher temperatures, the nose disappears and by 380/sup 0/C the familiar symmetrical bell-shaped curve predominates with the critical point defined by the top of the bell. The P-T curve of the three-phase assemblage determined in the present study is in agreement with previous workers. The NaCl content of the three-phase vapor, however, is much higher than some literature values at temperatures above 410/sup 0/C.
- Research Organization:
- Geological Survey, Menlo Park, CA
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 6913730
- Journal Information:
- Geochim. Cosmochim. Acta; (United States), Vol. 50:7
- Country of Publication:
- United States
- Language:
- English
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