Excess properties and isobaric (vapor+liquid) equilibrium at sub-atmospheric pressures of binary (1,2-propanediol+1,3-propanediol) system: Measurement and modelling

[Display omitted] •The experimental VLE data of binary system (1,2-propanediol+1,3-propanediol) at sub atmospheric pressures.•nD and ρ data of the binary mixture of (1,2-propanediol+1,3-propanediol) at temperatures from (298.15 to 318.15)K.•Lorentz–Lorentz equation for the estimation of molar refractivity, Rm, using refractive index and molar volume, Vm.•Calculated VmE, and V¯iE, and correlated with the four-parameter Redlich–Kister polynomial equation and PFP theory.•A comparative study of different mixing rules for predicting refractive index values. Experimental (vapor+liquid) equilibrium data were obtained at sub-atmospheric pressures of (6.66, 13.33, 19.99, 26.66, 33.33, 39.99 and 46.66)kPa for the binary system (1,2-propanediol+1,3-propanediol) over the entire composition range using Swietoslasky-type ebulliometer. Wilson and NRTL activity coefficient models were used to correlate the experimental VLE data for which optimum binary interaction energy parameters are reported. NRTL model fitted well with experimental data as compared to Wilson model. Density and refractive indices of binary mixtures are also reported along with their excess properties such as excess molar volumes (VmE), excess refractive index (nE), partial molar volume (V¯i), apparent molar volume (V∅i), and excess partial molar volume (V¯iE) at different temperatures (293.15 to 318.15)K. The excess molar volumes data were used to test the applicability of Prigogine–Flory–Patterson theory and refractive index values to test different mixing rules.