Absorption of ultrasonic waves in aqueous solutions of N-methylacetamide and zinc chloride

Abstract

Measurements of the absorption coefficient of ultrasonic waves have been made within the frequency range of 10–100 MHz in aqueous solutions of N-methylacetamide (NMAA) and zinc chloride (ZnCl2). The method used to prepare quasi-two-component solutions permitted a change in the ratio of the number of amide molecules to electrolyte molecules, given a constant number of water molecules. The results indicate the occurrence of a single relaxational process in the solutions under investigation and the frequency range adopted. On the basis of the theory of relaxational absorption of sounds, relaxation parameters as well as the enthalpy of activation of the solution in question, which was 16.4 kJ/mol, have been calculated. The character of the relaxational process observed was determined on the basis of the analysis of relaxational curves. The discovered relaxational process in H2O–NMAA–ZnCl2 was ascribed to the formation and disintegration of ‘‘solvatomers’’ composed of [NMAA Zn(H2O)3]2+.