Theory of vapor pressure osmometry when ambient solvent vapor is unsaturated

Abstract

AbstractThe general theory of the vapor pressure osmometry has been established, as an extension of the KAMIDE and SANADA theory, in the case when ambient vapor phase is unsaturated. The temperature difference (Tn–Tv)s at the steady state between a solution drop and a solvent drop can be expressed in a form of virial expansion of concentration c in the form: with equation image Tn and Tv are the temperatures of the solution and solvent drops, respectively, M1 the molecular weight of the solute, A2,v the second virial coefficient, R the gas constant, Ts the temperature of ambient vapor phase, δH the molar heat of condensation of the solvent, k1n and k2n the coefficients of heat transfer at the interfaces between vapor and the solution drop and between the solution and the thermistor, respectively, A1n the surface area of the solution drop, A2n the surface area of the thermistor in contact with the solution. P0(Ts) saturated vapor pressure of the solvent at the temperature Ts, k′ the saturation coefficient defined by the ratio of the real unsaturated pressure of ambient vapor phase to the saturated pressure at the same temperature, and V0 the molar volume of the solvent.Theoretical examination of k′ showed the difference between Ks and Ks is negligible, i.e., the first equation usually reduces to the corresponding equation derived previously by assuming that the ambient vapor phase is saturated.