Correspondling states correlations for liquid compressibility and partial molal volumes of gases at infinite dilution in liquids

Abstract

A statistical mechanical solution theory is used as the basis for corresponding states formulations. Universal functions relate the compressibility to the reduced density and the partial molar volume to reduced solvent density only. Correlations are in good agreement with data for all types of nonelectrolytes over wide ranges of temperatures including saturated and compressed systems. The correlations provide simple methods for describing the isothermal pressure dependence of liquid volumes and the pressure dependence of the ideal-solution solubility of gases in liquids. S. CONCLUSIONS AND SIGNIFICANCEFor all liquids the product of compressibility times temperature can be expressed to a high degree of accuracy as a simple function of reduced density only, Equation The single reducing volume is the critical volume for nonpolar substances but is empirically fitted for polar substances. The form of this relation allows a simple expression for the change in volume with an isothermal change in pressure and the entire liquid state can be described from the saturation volumes and the present correlation.The partial molal volume of gases at infinite dilution in liquids can be obtained to within a few yo from a simple function of reduced density of the solvent and the reducing volumes of the gas and solvent, Equations (9) to (11). This generalized expression provides the means to correct for the effect of pressure on Henry's constant as used to predict solubilities of gases. However, the present equation does not describe the partial molal volume of liquids in liquids; apparently the liquid volumetric behavior is different when a substance is above its critical temperature. The expressions for both compressibility and partial molal volume arise from use of a statistical mechanical solution theory involving integrals of the molecular direct correlation function. Their universality can be attributed to the lack of importance of nonspherical forces in the integral of the correlation function. However, it is not clear why the integrals are independent of temperature in the liquid region since essentially complete cancellation of the effects of temperature must occur in the (positive) long range and (negative) short range values of the correlation functions and there is no molecular theory which would predict this. THERMODYNAMIC PROPERTIESA knowledge of the compressibility of the liquidFor mixtures the partial molal volume is useful to de-scribe the volumetric behavior v = 8 x i u i (3) can be used to generate the equation of state for the liquid along an isotherm since the change of pressure which ocand to correct for the pressure dependence of liquid fugaccurs with a change in density is ity f

Pair correlation function integrals: Computation and use

“…(24) constitutes an approximate expression where only h(r) appears, instead of the whole (angular dependent) total correlation function. Equation (24) possibly constitutes a source of errors in addition to the various approximations for c(r). It is, based on the present data, difficult to discriminate the relative importance of these approximations.…”

“…Also, Gubbins and O'Connell 23 showed that for dense fluids the correlation function integrals for water and argon scaled with only two parameters. In addition, several studies show successful corresponding-states scaling for the direct correlation function integrals, [23][24][25][26][27][28][29] as described in detail in Ref. 46.…”

Mass transfer and thermodynamic modeling of carbon dioxide absorption into MEA aqueous solution

“…Where ψ ji is defi ned by the equation 28 as follow: (28) The interaction energy parameters of u ji and u ii are independent of composition, but are temperature dependent: (29) The combinatorial activity coeffi cient at infi nite dilution is 31 : …”

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