Abstract

MARTINEZ REYES, José; PEREZ, Renee J.; GONZALEZ PARTIDA, Eduardo  and  TINOCO MICHEL, Jorge A.. Equation for the Poynting correction in equilibrium thermodynamics between non-polar gas phases and aqueous systems: Application to the H₂S-H₂O-NaCl. Bol. Soc. Geol. Mex [online]. 2010, vol.62, n.2, pp.213-220. ISSN 1405-3322.

In this paper we used the semitheoretical expression for the partial molar volume at infinite dilution ofvolatile aqueous non-electrolyte solute (V₂⁰), developed by Plyasunov et al. (2000b) in order to propose a new equation for Poynting correction. The mathematical formula V₂⁰ considers as variables the density and isothermal compressibility of the solvent, as well as the second cross solvent-solute virial coefficient (β₁₂) and the second virial coefficient of pure solvent (β₁₁). The equation was integrated analytically with respect to pressure using some auxiliary correlations found in the literature, and thereby obtain a mathematical expression of the isothermal pressure increment of the standard (infinite dilution) Gibbs energy (or chemical potential) of the solute (ΔG₂⁰). The mathematical equation is applicable to solutes whose β₁₂ is known or can be estimated, in a temperature range of273.16 K to 647 K, values of pressure up to 2 kbar and brines with ionic strength equal to 6 m NaCl. The expression fits the experimental data very well, as shown for the H₂S-H₂O-NaCl system (with maximum deviation of 7%), through a thermodynamic model that uses this formula proposal coupled with the Law of Henry and the Soave-Redlich-Kwong equation of state for modeling the liquid-vapor phase equilibria. Similarly, we propose an alternative expression for calculating V₂⁰ (with similar values of maximum deviation).

Keywords : thermodynamic modeling; Poynting correction.