Vapor‐liquid equilibria in multicomponent aqueous solutions of volatile weak electrolytes

Abstract A molecular‐thermodynamic correlation is established for calculating vapor‐liquid equilibria in aqueous solutions containing one or more volatile electrolytes: ammonia, carbon dioxide, hydrogen sulfide, sulfur dioxide, and hydrogen cyanide. The correlation is similar to that presented in 1975, but the domain of application has been increased. The present correlation holds from about 0° to 170°C and for ionic strengths of about 6 molal; for the weak electrolytes considered here, this corresponds to total concentrations between 10 and 20 molal. To represent activities at these high concentrations, activity coefficients are expressed as a function of molality by Pitzer's equation. Required parameters are estimated from data reduction or from correlations. Special attention is given to the ternary systems ammonia‐carbon dioxide‐water and ammonia‐hydrogen sulfide‐water. Calculated equilibria are in satisfactory agreement with the severely limited experimental data now available.