The volumetric, calorimetric, acoustic, and optic properties of binary solutions of 1,3-butanediol + butylamine, or dibutylamine, or ethanolamine, or 1-amino-2-propanol were investigated. Density (ρ), speed of sound (u), and refractive index ( \({n}_{\text{D}}\) ) were measured across the entire composition range at (298.15, 308.15, 318.15) K and 81.5 kPa. Difference temperature between before and after mixing, \(\Delta\) T at 298.15 K was also determined. Upon these experimental parameters, the excess molar volume \({V}_{\text{m}}^{\text{E}}\) , excess partial molar volume \({\overline{V} }_{i}^{E}\) , excess molar enthalpy \({H}_{m}^{E}\) , excess partial molar enthalpy \({\overline{H}}_{m,i}\) , deviations in isentropic compressibility \({\Delta k}_{\text{s}}\) , or in refractive index \({\Delta n}_{\text{D}}\) were calculated. The \({V}_{\text{m}}^{\text{E}}\) , \({\Delta k}_{\text{s}}\) , \({H}_{m }^{E}\) , and \({\Delta \text{n}}_{\text{D}}\) were correlated using the Redlich–Kister equation. The Perturbed Chain Statistical Associating Fluid Theory (PC-SAFT) equation of state proved to be an effective tool for modeling the density and speed of sound for mixtures. Also the Free Length Theory (FLT) for speed of sound as predictive approach in these mixtures was applied. Additionally, three mixing rules were applied to predict the refractive index. The Wison, NRTL, and UNIQUAC models were also used to predict the excess molar enthalpies. These findings provide insights into intermolecular interactions, molecular size differences, and structural characteristics within mixtures.
