Indian Journal of Pure & Applied Physics Vol. 51, March 2013, pp. 202-206 Acoustic and ultrasonic studies of alkali metals and ammonium halides in chitosan solutions at four different temperatures M Talukdar a , D Moharatha b , G S Roy c & U N Dash a a Department of Chemistry, I T E R, Siksha ‘O’ Anusandhan University, Bhubaneswar 751 030, Odisha, India b Department of Physics, Silicon Institute of Technology, Bhubaneswar 751 024, Odisha, India c Department of Physics, G M College, Sambalapur, Odisha, India E-mail: malabika136@gmail.com Received 27 January 2012; revised 5 October 2012; accepted 4 January 2013 The densities of halides of potassium, sodium and ammonium have been measured in different chitosan solutions at 298.15, 303.15, 308.15 and 313.15 K and the ultrasonic velocity in these solutions has been measured at 298.15 K. Various parameters such as isentropic compressibility, acoustic impedance, apparent molar volume, partial molar volume, relative association, relaxation time, etc. have been calculated using experimentally determined values of ultrasonic velocity and density. The variation of these parameters has been discussed in the light of solute-solvent and solute-solute interactions. Keywords: Chitosan solutions, Alkali metal halides, Apparent molar volumes, Isentropic compressibility 1 Introduction Solvation dynamics 1,2 have been the focus of intense research activities for the past few years. Recent experimental and theoretical studies have given rise to renewed interest in this field 3,4 . Hence, some bulk properties like density (d) and ultrasonic velocity (U) that provide an insight into the intermolecular arrangements of the components in solutions and help to understand the thermodynamics and acoustic properties of the solutions, have been measured. Evaluation of partial molar quantities is of importance as they provide a lot of information regarding the ion-solvent interactions in various solutions. Since these quantities cannot be directly determined from the experiments, it is difficult to study the molecular interaction in ternary mixtures. However, these quantities are related to the corresponding apparent molar quantities which are directly determined. The objective of the present investigation is to determine the values of , d, U and related acoustic parameters and study the possible ion-ion and ion- solvent interactions for the solutions of KCl, NaCl, NH 4 Cl, in 0.01, 0.05, and 0.1% (w/v) chitosan in 0.1 molar HCl solution. Chitosan is derived from chitin a polysaccharide, which is also cellulose like polymer consisting mainly straight chains of N-acetyl-D- glucosamine. Since chitosan finds wide applications in agriculture, horticulture, water filtration process, biomedical and industrial materials, the present work aims at determining the physico-chemical properties of the halides in chitosan solutions. 2 Theory The apparent molar volume V φ has been calculated from the density data 5 by the standard Eq. (1). V φ = 1000 1 0 ( ) cd - (d 0 -d) + 1 0 Md - … (1) where c is the molar concentration, d 0 the density of the solvent, d the density of the solution and M is the molar mass of the solute. The V φ data have been fitted to the Masson equation by least square method 5 and the limiting apparent volume, V φ 0 has been determined by the Eq. (2). V φ = V φ 0 + S v c 1/2 … (2) where S v is the slope of the V φ versus c 1/2 plot. The apparent molar expansibility E φ was calculated 5 by using Eq. (3). φ E =  0 φ V + (- o ) 1000 c -1 … (3) where  and  0 are the coefficients of expansion of the solution and solvent, respectively and have been obtained from the usual relation 5,6 . The E φ data 5 were fitted into the Masson Eq. (4) to get the limiting apparent expansibility (E φ 0 ) and the slope (S E ).