TY - JOUR
T1 - Precise measurement of the activity/composition relations of H2O-N2 and H2O-CO2 fluids at 500°C, 500 bars
AU - Anovitz, Lawrence M.
AU - Blencoe, James G.
AU - Joyce, David B.
AU - Horita, Juske
N1 - Funding Information:
This research was sponsored by the Division of Engineering and Geosciences, Office of Basic Energy Sciences, U.S. Department of Energy under contract DE-AC05-96OR22464 with Oak Ridge National Laboratory, managed by Lockheed Martin Energy Research Corporation, and by National Science Foundation Grant number NSF EAR 9590695. Leon Maya and Carlos Bamberger provided valuable advice concerning the use of nitrides as sources of nitrogen in hydrothermal experiments. The alundum and steel mesh used in our Shaw membranes were supplied free-of-charge by Saint-Gobian/Norton Industrial Ceramics Corp. (Norton Materials) and Buckbee-Mears Corp., respectively. Reviews by I-Ming Chou, Dave Wesolowski, and an anonymous reviewer were helpful and greatly appreciated.
PY - 1998/3
Y1 - 1998/3
N2 - The activity/composition relations of H2O-N2 and H2O-CO2 fluids have been measured at 500°C, 500 bars. The results are more accurate, and much more precise, than any currently available, especially for H2O-poor compositions. Samples were reacted at fixed water activities (0.062 ≤ aH2o ≤ 0.777), using Cu3N as the source of N2, and Ag-oxalate as the source of CO2. After each experiment the masses of water and gas in the samples were analyzed manometrically. Results depend on the value used for the hydrogen fugacity for pure H2O in equilibrium with the oxide buffer, but using a newly measured value for Ni-NiO and fitting the data to a two-parameter Margules equation yields: for H2O-N2 fluids: WG,H2o = 3455.0 J/mol, WG,H2o = 3455.0 J/mol, WG,N2 = 1990.l J/mol; and for H2O-CO2 fluids: WG,H2o = 3882.5 J/mol, WG,co2 = 4902.6 J/mol. As uncertainties are not orthogonal, standard errors cannot be given. The data suggest that H2O-CO2 fluids exhibit large positive deviations from ideality at 500°C, 500 bars, in marked contrast to values predicted by available equations of state. These results indicate that more accurate models for both H2O-N2 and H2O-CO2 fluids are needed.
AB - The activity/composition relations of H2O-N2 and H2O-CO2 fluids have been measured at 500°C, 500 bars. The results are more accurate, and much more precise, than any currently available, especially for H2O-poor compositions. Samples were reacted at fixed water activities (0.062 ≤ aH2o ≤ 0.777), using Cu3N as the source of N2, and Ag-oxalate as the source of CO2. After each experiment the masses of water and gas in the samples were analyzed manometrically. Results depend on the value used for the hydrogen fugacity for pure H2O in equilibrium with the oxide buffer, but using a newly measured value for Ni-NiO and fitting the data to a two-parameter Margules equation yields: for H2O-N2 fluids: WG,H2o = 3455.0 J/mol, WG,H2o = 3455.0 J/mol, WG,N2 = 1990.l J/mol; and for H2O-CO2 fluids: WG,H2o = 3882.5 J/mol, WG,co2 = 4902.6 J/mol. As uncertainties are not orthogonal, standard errors cannot be given. The data suggest that H2O-CO2 fluids exhibit large positive deviations from ideality at 500°C, 500 bars, in marked contrast to values predicted by available equations of state. These results indicate that more accurate models for both H2O-N2 and H2O-CO2 fluids are needed.
UR - http://www.scopus.com/inward/record.url?scp=0031694388&partnerID=8YFLogxK
U2 - 10.1016/S0016-7037(98)00027-1
DO - 10.1016/S0016-7037(98)00027-1
M3 - Article
AN - SCOPUS:0031694388
SN - 0016-7037
VL - 62
SP - 815
EP - 829
JO - Geochimica et Cosmochimica Acta
JF - Geochimica et Cosmochimica Acta
IS - 5
ER -