and the variation with S of the volume of revolution V = 116'2 and surface area of revolution A = ac are given by A system of equations based on the ionic atmosphere theory of Debye and Huckel, Born model contribution, and local compositions of the nonrandom two-liquid (NRTL) model is developed to represent isothermal activity coefficients, in the whole range of concentrations, for solutions in an undissociated solvent of a partially or completely dissociated electrolyte. The physical constants and the four adjustable parameters necessary to represent the osmotic coefficient, for fifteen strong aqueous electrolytic SOlutions, are given at 298.15OK and atmospheric pressure. Vapor-liquid equilibrium, for the hydrochloric acid-water system at 298.15OK, is represented for acid compositions ranging from infinite dilution to 18 M using a known dissociation constant and six parameters. SCOPE

New vapor-liquid equilibrium data were determined, at atmospheric pressure by a dynamic method, for liquid mole fractions of acetic acid from 5 X 10"7 to 4 X 10'2. The behavior of the system at high dilutions is explained by the ionic dissociation of the electrolyte. The treatment of these data, assuming ideal behavior of all the species, yields a value of the Henry's constant of the undissociated acid, using a literature value of the dissociation constant of the acid. This Henry's constant is consistent with that resulting from the treatment of data at high concentrations where the dissociation of the acid can be neglected. A representation of the vapor-liquid equilibrium data, at atmospheric pressure, for mole fractions of acetic acid in the liquid between 5 X 10"7 and 0.95 is given.