Excess properties of binary mixtures of tri–iso-amyl phosphate + n–hexane (or n-dodecane): Physical significance of coefficients of Redlich-Kister type equation

Abstract

Present study incorporates thermodynamic analysis of data obtained by accurate measurement of density and viscosity of binary liquid mixtures of tri–iso-amyl phosphate and n–hexane (or n–dodecane). Law of density and viscosity of binary liquid mixtures is given as follows: Density and logarithmic viscosity of binary mixtures are nth (1≤n≤4) order polynomials of mole fraction of one of the component at constant temperature, and parametric coefficients of such polynomials are mth (1≤ m≤3) order polynomials of absolute temperature. A dimensionless Redlich–Kister equation (RK-EoS) of state is introduced to decipher physical significance of coefficients of RK-Eqn, by comparing with the same order of Virial equation of state (Virial-EoS). Physical significance of coefficients of RK-EoS is similar to that of significance of virial-coefficients in thermodynamic Virial Equation, in terms of molecular interactions. Parametric coefficients of RK-EoS are directly proportional to the corresponding virial coefficient of Virial–EoS and inversely proportional to both mole fraction difference and molar volume of mixture of the same order of virial coefficient. Coefficients of Vogel’s equation of viscosity have been found to be polynomial of mole fraction of one of the component of binary mixtures.