“ STUDY OF SOLVENT-SOLVENT INTERACTION IN A AQUEOUS MEDIUM AT DIFFERENT TEMPERATURES BY ULTRASONIC TECHNIQUE ”

The basic parameters like velocity (U), density(ρ) and viscosity (η) can be measured by ultrasonic Interferometer. From these parameters various thermodynamical and acoustical parameters such as adiabatic compressibility 's (β), specific acoustic impedance (Z), Solvation number (S ), Intermolecular free length (L ), have been estimated using standard relations from n f 0 0 measured values of Ultrasonic velocities, densities and viscosities in the wide range of concentrations at 35 C, 40 C and 0 45 C temperatures for Acetone + Propanol – 2 +Toluene tertiary system. The solvent-solvent interactions are studied on the basis of increase or decrease in ultrasonic velocity, density, viscosity and other derived acoustical parameters in terms of structure making and structure breaking tendencies of various solvent molecules.


I. INTRODUCTION
Developments which are taking place in this field have found great use of ultrasonic energy in the field of medicine, engineering, agriculture, technology and industry [5,6]. In chemical industries, ultrasonic energy is found useful in studying the chemical processes as well as different types of reactions in synthesis of chemical substances. Wong and Zhu [7] have studied the speed of sound in seawater as a function of salinity, temperature and pressure. Skumiel and Labowski [8] have given a theoretical analysis of the effect of an external constant magnetic field on the propagation of ultrasonic waves in electrically conducting liquids as well as the results of measurements carried out in mercury. Hanel [9] has analytically deduced an equation for the longitudinal sound velocity of thin film samples and the velocities of the tertiary liquid mixtures have been calculated. The compositional dependence of thermodynamic properties has proved to be a very useful tool in understanding the nature and extent of pattern of molecular aggregation resulting from intermolecular interaction between components. Ultrasonic waves with low amplitude have been used by many researcher to investigate the nature of molecular interactions and physio-chemical behavior of pure, binary, ternary and quaternary liquid mixtures.
A survey of literature indicates that excess values of acoustical parameters are useful in understanding the nature and strength of the molecular interaction in the pure, binary, ternary and quaternary liquid mixtures . Acoustic and thermodynamic parameters have been used to understand different kinds of association, the molecular packing, molecular motion and various types of intermolecular interactions and their strengths, influenced by the size in pure components and in the mixtures.

II. EXPERIMENTAL STUDIES
Ultrasonic velocity was measured using single crystal ultrasonic interferometer of 2 MH z frequency (Model M81) supplied by Mittal Enterprises, New Delhi, that has a reproducibility of 0.4ms -1 at 25 o C.The temperature was maintained constant by circulating water from a thermostatically controlled water bath (accuracy 0.1 0 C).The temperature of the cell was measured using a thermocouple (at the crystal) and found to be accurate The chemicals used were of AR grade, procured from BDH. All the chemicals were purified by standard procedures discussed by Armarigo and Perrin before use. Tertiary system is studied at different temperatures,

III. THEORY
Various physical parameters were evaluated from the measured values of ultrasonic velocity (U) and density (ρ) using the following standard formulae: Where k values for different temperatures were taken from the work of Jacobson; at 35,40 and 45 o C the K values are 637, 642 ,647 respectively.
where V and M are the molar volume and molecular weight of the mixtures, respectively.
Specific acoustic impedance (Z) =ρU (5) and the excess adiabatic compressibility (β E ) and excess intermolecular free length (L f E ) can evaluated by the following expressions: For β ideal and L f.ideal , the densities and the ultrasonic velocities of various components in pure state at the three given temperatures have been measured. Further, the velocities of both the systems at different concentrations and temperatures have been evaluated theoretically using volume additive rule as : Where U 1, U2 , and U 3 are the velocities of the three components of the ternary liquid mixture in pure state and , and are their volume fractions.

IV. RESULTS
Ultrasonic velocity, density, viscosity ,adiabatic compressibility and specific acoustic impedance for the acetone-propanol-2 and Toluene have been listed in

V. DISCUSSION
It is seen from the data that in Acetone, Propanol-2 and Toluene system ultrasonic velocity increases initially as When the temperature is increased the velocity maxima shifts towards lower concentration. This is because of the thermal energy which facilitates the breaking of bonds between the associated molecules of Acetone, Propanol-2 and Toluene. The increase in thermal energy weakens the molecular forces and hence decrease in velocity is expected. The observed acoustical parameters and their variation and temperature clearly indicate that the formation of complex between unlike molecules through hydrogen bonding.
From Table 1  At low temperature, these molecules may stay in associated form. The associated molecules are fairly in large size as compared to Propanol -2 and Acetone and Toluene may cause some structural changes resulting in the weakening of the intermolecular forces. The adiabatic compressibility (β) and intermolecular free length (L f ) both have an inverse relationship with ultrasonic velocity. The decrease in β with increase in concentration is an indicative fact that intermolecular forces are increasing which brings the molecules to a closer packing resulting into a decrease in L f .The specific acoustic impedance is governed by the initial and elastic properties of the medium. Therefore it is important to examine specific acoustic impedance in relation to concentration and temperature.
When the temperature is increased the velocity maxima shifts towards lower concentration. This is because of the thermal energy which facilitates the breaking of bonds between the associated molecules of Acetone, Propanol-2 and Toluene. The increase in thermal energy weakens the molecular forces and hence decrease in velocity is expected. The observed acoustical parameters and their variation and temperature clearly indicate that the formation of complex between unlike molecules through hydrogen bonding. The Ultrasonic studies provide comprehensive investigations between Acetone+ Propanol-2 + Toluene molecules arising dipole-dipole interactions.