Volumetric properties and refractive indices of butanol isomers + diethyl phthalate binary mixtures at T = (293.15, 303.15 and 313.15 K) and atmospheric pressure (0.082 MPa)

Abstract

The density (ρ), and refractive index (n_D) of three binary mixtures containing 1-butanol, 2-butanol, and 2-methyl-2-propanol with diethyl phthalate (DEP) were studied over the whole range of composition at different temperatures from 293.15 to 313.15 K, and atmospheric pressure (0.082 MPa). Experimental data were used to calculate the excess molar volumes ($V_m^E$) and deviation in refractive indices ($\Delta n_D$). The experimental density values were used to calculate the partial molar volumes (${\overline{V}}_{m,i}$), apparent molar volumes ($V_{\varnothing ,i}$), partial molar volumes at infinite dilution (${\overline{V}}_{m,i}^{\infty }$), and excess partial molar volumes (${\overline{V}}_{m,i}^E$). A Redlich-Kister type polynomial equation is used with the method of least-squares to set up a correlation between excess molar volumes and deviation in refractive indices, leading to the estimation of binary coefficients and standard errors. Theoretical refractive index values were calculated using seven relations, namely Arago–Biot (A–B), Dale–Gladstone (D–G), Lorentz–Lorenz (L–L), Heller (H), Weiner (W), Newton (Nw) and Eyring and John (E-J). This study examines how composition and temperature affect the variation of parameters in these mixtures, considering molecular interactions. Experimental data and results provide useful information for further thermodynamic studies of alcohol-ester mixtures.