A modified Redlich-Kwong equation of state for H2-H2O fluid mixtures at high pressures and at temperatures above 400°C
Grevel, Klaus-D.; Chatterjee, Niranjan D.
European Journal of Mineralogy Volume 4 Number 6 (1992), p. 1303 - 1310
published: Dec 15, 1992
manuscript accepted: Mar 13, 1992
manuscript received: Aug 19, 1991
ArtNo. ESP147050406024, Price: 29.00 €
Abstract Redox equilibria relevant to the crust and mantle of the earth may be viewed as reactions between solids and a fluid mixture comprising H2 and H2O. Thus, thermodynamic treatment of redox equilibria requires that the fugacities and activities of H2 and H2O in such a fluid mixture be known for high temperatures and pressures. Modified Redlich-Kwong (MRK) equations of state for H2, H2O, and H2-H2O mixtures, given below, are capable of generating reliable fugacity and activity data at temperatures above 400°C, although pure component fugacities may also be computed with considerable accuracy at lower temperatures. The activity coefficients returned by the MRK are compatible with the constraints put by the Gibbs-Duhem equation. A significant positive deviation from ideality is encountered to as high a temperature as 800°C; this should be considered in computing redox equilibria. A computer program generating the fugacities and activities of H2 and H2O at desired T, P, and XH2 may be obtained on request from the first author.