Ultrasonic Velocity Measurements and Adiabatic Compressibility Analysis in Ethanol, Propan-2-ol, and Diethylene Glycol: A Comparative Study Using Interferometric Technique

Background: The ultrasonic interferometry gives a precise non-destructive method for investigating molecular interactions and thermodynamic properties of liquids through acoustic parameter measurements. Objective: Our study aimed to determine ultrasonic velocity and adiabatic compressibility in three industrially and scientifically important liquid 1. Ethanol, 2. Propan-2-ol (isopropanol), 3. Diethylene glycol with a high-frequency ultrasonic interferometer operating at 2 MHz. Methods: As our measurements conducted at room temperature (34-37°C) using a Mittal-type ultrasonic interferometer with a measuring cell of 0.01 mm least count. We have taken multiple readings for each liquid to ensure statistical reliability. We have calculated ultrasonic velocity from wavelength measurements, and also adiabatic compressibility was derived using the Laplace-Newton equation. Results: The mean ultrasonic velocities obtained were: ethanol (1125.12 ± 2.71 m/s), propan-2-ol (1111.58 ± 9.11 m/s), and diethylene glycol (1584.79 ± 31.30 m/s). Corresponding adiabatic compressibilities were: ethanol (1.0012 ± 0.0048 × 10⁻⁹ m²/N), propan-2-ol (1.0298 ± 0.0169 × 10⁻⁹ m²/N), and diethylene glycol (0.3564 ± 0.0139 × 10⁻⁹ m²/N). Conclusions: As diethylene glycol exhibited significantly higher ultrasonic velocity and lower compressibility compared to the alcohols, attributed to stronger intermolecular hydrogen bonding and higher molecular weight. While the inverse relationship between ultrasonic velocity and adiabatic compressibility was confirmed. So these findings contribute to understanding molecular interactions in organic liquids and have implications for industrial applications in fuel quality assessment, pharmaceutical formulations, and material characterization.