Calculation of the thermodynamic and transport properties of aqueous species at high pressures and temperatures: Correlation algorithms for ionic species and equation of state predictions to 5 kb and 1000°C

Thermodynamic/electrostatic properties of H 20 at high pressures and temperatures were calculated from regression equations representing dielectric constant data reported by Oshry (ms), Owen and others (1961), and Heger (lllS) for temperatures and pressures froln 0° to 550°C and 0.001 to 5 kb together with finite difference derivatives computed from specific vC9lullles given by Burnham, Hollo,vay, and Davis (1969b) for 20° to 900°C and 1 to 10 kb. Corresponding properties belo'v a kilobar ,vere conlputed with the aid of the equation of state developed by Keenan and others (1969), 'which describes the thermodynamic behavior of I-I~O in close accord ,vith the tolerances of the International Skeleton Tables of 1963. The results of the calculations are given in equations, tables, and diagrams depicting isothenns, isobars, and isopleths of specific volume, entropy, enthalpy, internal energy, Helmholtz and Gibbs free energies, fugacity, and heat capacity, together with the dielectric constant, coefficients of isobaric thermal expansion and isothermal compressibility, the Born (1920) free energy function, and their partial derivatives. Perturbation of the thermodynanlic/electrostatic behavior of H 20 by the critical phenomenon lead·~ to significant differences in the dependence of its properties on temperature, pressure, and density above and below ---' 400°C and ~ 1 to 2 kb. The calculations permit prediction of the consequences of these differences on the chemical interaction of Ininerals and aqueous electrolyte solutions in geochemical processes.

Theoretical prediction of the thermodynamic behavior of aqueous electrolytes at high pressures and temperatures; I, Summary of the thermodynamic/electrostatic properties of the solvent

The thermodynamics of the carbonate system in seawater

As suggested in a previous study under the title “Simple Relationship Between the Properties of Isotopic Water”, viscosity results verify the fact that the structural properties of liquid H2O and D2O are nearly identical once a zero-point-energy-induced thermal offset effect is taken into account. This means that the viscosities of these two isotopic forms must be compared at different temperatures, rather than at the same temperature. Only in this way can the expected (MD2O/MH2O)1/2 viscosity ratio be retrieved. Application of this most simple idea, with no additional parameter adjustment, to H2O viscosity data, or equivalently to any of the existing empirical viscosity equations for H2O, leads to D2O viscosities having better than 1% accuracy over a wide temperature range. This isotopic correlation concept has also been used here to predict viscosities of liquid T2O, no viscosity data apparently being available for this substance.

Thermal Offset Viscosities of Liquid H2O, D2O, and T2O

Reaction volumes ΔVo at infinite dilution and 25°C are obtained by use of a Hashitani dilatometer for protonic ionizations of buffering agents. Combined with recent finding by Hamann that the pressure dependence of the activity coefficient can be estimated by the limiting Debye-Hueckel law even at high ionic strength, one can predict the pH and pOH for these buffer solutions at high pressure.

Reaction volume of protonic ionization for buffering agents. Prediction of pressure dependence of pH and pOH

Isothermal compressibility of aqueous sodium chloride, magnesium chloride, sodium sulfate, and magnesium sulfate solutions from 0 to 45.deg. at 1 atm

Density and viscosity of deuterium oxide solutions from 5-70.deg.

The apparent molal volumes of dilute (0.002 to 1.0m) aqueous HCl and NaOH solutions have been determined at 0, 25, and 50°C and NaCl solutions at 50°C. The partial molal volumes (
 
$$\bar V$$

 ) of HCl, NaOH, and NaCl solutions have been determined from these apparent molal volumes and other reliable data from the literature. The partial-molal-volume changes (
 
$$\Delta \bar V_1 $$

 ) for the ionization of water, H2O→H++OH−, have been determined from 0 to 50°C and 0 to 1m ionic strength from the partial molal volumes of HCl, NaOH, NaCl, and H2O. The partial molal compressibilities (
 
$$\bar K$$

 for HCl, NaOH, NaCl, and H2O have been estimated from data in the literature and used to determine the partial molal compressibility changes (
 
$$\Delta \bar K_1 $$

 ) for the ionization of water from 0 to 50°C and 0 to 1m ionic strength. The effect of pressure on the ionization constant of water has been estimated from partial-molal-volume and compressibility changes using the relation
 
$$RTln(K^P /K) = - \Delta \bar V(P - 1) + \tfrac{1}{2}\Delta \bar K(P - 1)^2 $$

 from 0 to 50°C and 0 to 2000 bars. The results agree very well with the directly measured values.

Edward V. Hoff

Papers

Isothermal compressibility of aqueous sodium chloride, magnesium chloride, sodium sulfate, and magnesium sulfate solutions from 0 to 45.deg. at 1 atm

Density and viscosity of deuterium oxide solutions from 5-70.deg.

The effect of pressure on the ionization of water at various temperatures from molal-volume data1