Thermodynamics of binary liquid mixtures of partially deuterated methanes with CH4 or CD4

Abstract

Articles you may be interested inThermodynamical and structural properties of binary mixtures of imidazolium chloride ionic liquids and alcohols from molecular simulation Structure, thermodynamics, and dynamics of the liquid/vapor interface of water/dimethylsulfoxide mixtures The vapor pressure isotope effect of samples of isotopically substituted methane and their mixtures was measured as a function of temperature and mixture composition: The differential vapor pressure between CH i D 4Ϫi ͑with iϭ0 or 4͒ and CH j D 4Ϫ j ͑with jϭ1, 2, or 3͒, the differential vapor pressure between mixtures of (CH i D 4Ϫi ϩCH j D 4Ϫ j ) and CH 4 ͑if iϭ4͒ or CH j D 4Ϫ j ͑if iϭ0͒ and the absolute vapor pressure of CH 4 ͑if iϭ4͒ or CH j D 4Ϫ j ͑if iϭ0͒, were measured simultaneously between 96 and 121 K for mixtures of nominal composition 0.25, 0.50, and 0.75 mole fraction in the reference methane species. The p(x,T) data were used to calculate the excess molar Gibbs energy function, G E (x,T) and the excess molar enthalpy H E (x), assuming that this last function is independent of temperature in the experimental range. The deviations from ideal behavior are very small, G E being only some tenths of J/mol for equimolar mixtures. The experimental G E values compare well with estimated results based on a modified version of the statistical theory of isotope effects in condensed phases. Comparisons with reported values of the liquid-vapor isotope fractionation factor for the CD 3 H-CH 4 system are also made.