Ultrasonic, optical and IR studies of binary mixtures of morpholine with some aromatic hydrocarbons at TÂ =Â (303.15, 308.15 and 313.15) K

In this paper, the speed of sound, (U), and refractive index (nD) of four binary systems (morpholine + aromatic hydrocarbons) are measured along the whole composition range, at 303.15, 308.15 and 313.15 K and at normal pressure. Furthermore, the FT-IR measurements of these mixtures are carried out at 298.15 K to study the complex formation between morpholine and aromatic hydrocarbons. From the experimental data, deviation in speed of sound, (ΔU), isentropic compressibility, (KS), excess isentropic compressibility, (KSE), acoustic impedance, (Z), deviation in acoustic impedance, (ΔZ), and deviation in refractive index (ΔnD) are calculated and satisfactorily fitted using the Redlich-Kister polynomial equation. These values are reported as a function of mole fraction, (X1) or volume fraction (ϕ1) of morpholine. Moreover, theoretical speed of sound and average deviations is calculated using well established equations like Nomoto (NMT), Ideal Mixing Rule (IMR) and Jacobson's Free Length Theory (FLT). A comparative study of nine mixing rules of refractive index studies namely Arago-biot, Dale-Gladstone, Lorentz-Lorentz, Eykman, Weiner, Heller, Newton, Oster and Eyring-John has been reported to investigate their validity for these mixtures over the entire mole fraction of morpholine at three temperatures. Comparison of these nine mixing rules has been presented in terms of average deviation. The FT-IR results show that the maximum interactions are observed in morpholine + benzene binaries, and these results are supported by the speed of sound and refractive index data.