Density, viscosity and refractive index of binary liquid mixtures at 293.15, 298.15, 303.15, 308.15 and 313.15 K

► Application of associated and non-associated processes to weakly interacting liquids. ► Application of McAllister model to physical properties (refractive index and viscosity both). ► Prediction of mixture properties obtained from different models and their comparison. ► Prediction of mixing function deviations (Δ η, Δ n). ► It is our first attempt to correlate the associated and non-associated properties of liquids. Densities, viscosities and refractive indices were measured for the binary liquid mixtures formed by formamide, N-methylacetamide, di-methylformamide and di-methylacetamide with acetonitrile at ( T = 293.15, 298.15, 303.15, 308.15 and 313.15) K and atmospheric pressure over the whole concentration range. Lorentz–Lorentz (L–L) relation, Prigogine–Flory–Patterson model (PFP), model devised by Glinski and Ramaswamy and Anbananthan (RS) models were used to study the associational behavior of weakly interacting liquids from viscosity and refractive index data. These non-associated and associated models were compared and also tested for different systems. The measured properties were fitted to Redlich–Kister polynomial relation to estimate the binary coefficients and standard errors. Furthermore, McAllister multi body interaction model was used to correlate the binary properties. Conclusively, viscosities and refractive indices of binary liquid mixture can be better understood from these models and interactions and association constant can be well predicted. The associated processes yield fair agreement between theory and experiment as compared to non-associated processes.