Complexation Studies in the Water-Zinc Acetate-Dimethylsulfoxide System Using the Ultrasonic Method

Measurements the ultrasonic velocity (at 1.814 MHz) and coefficient of ultrasonic absorption (at 2… 50 MHz) in aqueous solutions of dimethylsulfoxide (DMSO) and zinc acetate Zn(CH₃COO)₂ at 20°C have been performed. The MATEC equipment was used to these measurements. The investigation of molar volume and molar compressibility excess functions shows on the stronger intermolecular interaction between water and DMSO molecules than water and zinc acetate one. The addition of electrolyte (zinc acetate) to aqueous solutions of nonelectrolyte (DMSO) do not destroy the structure created by an interaction: water-DMSO molecules. This structure is modified trough association the part of molecules of water and DMSO in the solvation's complexes. For the creation of solvation's complexes indication the dependencies of differences in molar volume and molar compressibility between three- and two components solutions. It shows at the creation the solvatomers with a composition of [Zn(H₂O)₃(DMSO)₂]²⁺. The performed analysis of the measurements of ultrasonic waves attenuation in the range 2–50MHz indicates that in the studied frequency band two relaxation processes occur. These processes are attributed to the disturbance of equilibrium between both the solvation complexes (solvatomers) and outer-outer sphere complexes as well as the outer-sphere complexes.