An experimental determination of the thermodynamic properties of H[sub 2]O-CO[sub 2]-NaCl fluids at high pressures and temperatures

Journal Article · Mon Feb 01 00:00:00 EST 1993 · Geochimica et Cosmochimica Acta; (United States)

DOI:https://doi.org/10.1016/0016-7037(93)90165-S· OSTI ID:6673423

Joyce, D B; Holloway, J R ^[1]

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1. Arizona State Univ., Tempe (United States)

Understanding the role of fluids in geological processes requires a knowledge of the mixing properties of common geological fluids. A technique for experimentally determining activity coefficients for H[sub 2]O in fluid mixtures at pressures and temperatures accessible to the internally heated pressure vessel (10 kbar, 1100[degrees]C) is presented which used a new f[sub H[sub 2]O] buffer. The f[sub H[sub 2]O] buffer involves the simultaneous control of f[sub O[sub 2]] (with Ni/NiO) and f[sub h[sub 2]] (with a hydrogen membrane), thereby buffering f[sub H[sub 2]O] or equivalently, a[sub H[sub 2]O] through the reaction H[sub 2] + [1/2]O[sub 2] = H[sub 2]O. After quenching the run, the sample is analyzed to determine the X[sub H[sub 2]O] and, thus, the activity-composition relation for H[sub 2]O (a[sub H[sub 2]O] - X[sub H[sub 2]O]). Reversals are obtained by simultaneously running capsules loaded with low and high X[sub H[sub 2]O], thereby allowing the equilibrium X[sub H[sub 2]O] to be approached from both directions. Data were collected primarily in the H[sub 2]O-CO[sub 2] system at 2 kbars, 550-850[degrees]C, and at 4 kbars, 650[degrees]C. At those conditions, the H[sub 2]O-CO[sub 2] system generally shows small positive deviations from ideality. These results are in good agreement with the predictions of the MRK equation of state of HOLLOWAY (1977) at low T(T = 550[degrees]C) and are in good agreement with the predictions of the MRK equation of state of KERRICK and JACOBS (1981) at higher temperatures. At two conditions (2 kbar, 750[degrees]C; 4 kbar, 650[degrees]C), negative deviations from ideality are indicated at high X[sub H[sub 2]O]. Some data were also collected in the H[sub 2]O-NaCl and H[sub 2]O-CO[sub 2]-NaCl systems. In the former, H[sub 2]O shows small positive deviations from ideality at 2 kbars, 850[degrees]C, which increase with decreasing X[sub H[sub 2]O]. In the H[sub 2]O-CO[sub 2]-NaCl system, isofugacity lines for H[sub 2]O were measured.

• DOE Contract Number: AC05-84OR21400
• OSTI ID: 6673423
• Journal Information: Geochimica et Cosmochimica Acta; (United States), Vol. 57:4; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
58 GEOSCIENCES
CARBON DIOXIDE
THERMODYNAMIC PROPERTIES
MIXTURES
SODIUM CHLORIDES
WATER
CONTROL
EQUILIBRIUM
FLUIDS
HYDROGEN
MIXING
QUENCHING
ALKALI METAL COMPOUNDS
CARBON COMPOUNDS
CARBON OXIDES
CHALCOGENIDES
CHLORIDES
CHLORINE COMPOUNDS
DISPERSIONS
ELEMENTS
HALIDES
HALOGEN COMPOUNDS
HYDROGEN COMPOUNDS
NONMETALS
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
SODIUM COMPOUNDS
400201* - Chemical & Physicochemical Properties
580000 - Geosciences