Ultrasonic studies on dilute solutions of water in <i>n</i>-alcohols and 2-alkoxyethanols

Abstract

Ultrasonic velocities in dilute solutions of water in <i>n</i>-alcohols (methanol, ethanol, <i>n</i>-propanol and <i>n</i>-butanol), and 2-alkoxyethanols (2-methoxyethanol, 2-ethoxyethanol and 2-butoxyethanol) have been determined at 298.15 K using single crystal variable path interferometer working at 3 MHz. The excess ultrasonic velocities have been evaluated using the formula, which is thermodynamically valid. A distinctive non-linear variation of ultrasonic velocity with concentration of water in both n-alcohols and 2-alkoxyethanols has been observed over a small range of concentration. A similar behaviour is also observed in the concentration dependence of excess ultrasonic velocity in these solutions. This behaviour has been explained by considering the existence of water molecules as monomers up to certain optimum concentration, (<i>X</i>₂)_opt, of water and the non-linear behaviour observed beyond (<i>X</i>₂)_opt has been explained in the light of water-water and water-alcohol interactions leading to the formation of islands of water-alcohol extended structures.