Available on line www.jocpr.com Journal of Chemical and Pharmaceutical Research __________________________________________________ ISSN No: 0975-7384 CODEN(USA): JCPRC5 J. Chem. Pharm. Res., 2011, 3(3):432-438 432 Acoustical study of aqueous manganese chloride solutions at varying temperatures by ultrasonic technique 1 B. R Shinde., 2 Suresh S. Jadhav, 2 Sangita U. Shinde, 3 D.R. Shengule and 2 K. M. Jadhav 1 Department of Engineering Sciences, SRES’S College of Engineering, Kopargaon(MS), India, 2 Department of Physics, Dr. Babasaheb Ambedkar, Marathwada University, Aurangabad(MS), India 3 Department of Physics, Vivekanand College of Arts, Commerce and Science, Aurangabad (MS), India ______________________________________________________________________________ ABSTRACT Ultrasonic velocities, densities and viscosities in very dilute concentrations of aqueous MnCl 2 .4H 2 O system have been determined at 303.15K, 308.15K, 313.15K and 318.15K temperatures. Using this data, the acoustical parameters such as adiabatic compressibility’s (β), intermolecular free lengths (L f ), specific acoustic impedances (Z) and solvation numbers (S n ) have been estimated. The results have been interpreted in light of ion-solvent interactions in terms of structure breaking and structure promoting nature of Mn +2 ions in aqueous media. Keywords: ultrasonic velocity, ion-solvent interactions, adiabatic compressibility, intermolecular free length, solvation number. ______________________________________________________________________________ INTRODUCTION The study of molecular interactions in the liquid mixtures is very much important to study the structural properties of molecules. Ultrasonic energy is used in medicine, engineering, agriculture, defence and industry. In chemical industries ultrasonic energy is found useful in studying the chemical processes and in synthesis of chemical substances. In solution of ionic solute the attraction between the solute and solvent is of ion-dipole type. When electrolyte is dissolved in solvent it causes volume contraction due to interactions between ions and solvent molecules and therefore other acoustical parameters may be affected. Many researchers have used ultrasound to investigate the ion-solvent interactions in aqueous solutions containing electrolytes [1, 6]. A survey of literature [1-18], reveals that ultrasonic waves with low amplitude