Indian Journal of Chemi stry Vol. 44A, Sep tember 2005, pp. 1834- 1837 Ultrasonic me as urements in solutions of electrolytes in dimethyl sulfoxide + water mixtures at different temperatures Rit a Mehra Departme nt of Pure and Applied Chemi stry, MDS Un i versity, Ajmc r 305 009, India Received 29 lillie 2004; revised 27 lil ly 2005 Emai l: mehra_rita @rcd iffmail. co m Ultraso un d speed and densit y of el ec t ro ly tes CdCI 2 + KCI have been rneas ured in DMSO and H 2 0 mix tu res at 2 MHz from 25 to .45°C. Various derived parameters such as aco ustic impedance, adiabatic co mpress ibili ty and so l va ti on number ha ve been ca lcu!ated. The results have been di sc ussed in terms of the nature of el ec troly te and sol ve nt mixtures. So lvation number throws light on th e so lute-solu te and so lut e-so l ven t interactions. IPC Code: In1. Cl 7 BOIJ 19/ 10 In recent years, there has been cons id era bl e progress in the determination of thermodynami c, acoustic and transport properties of working fluids from sound speed, den s it y a nd viscosity measurements l -4, Transport properties of electrolytes in aq ueo us, non aqueous and mixed solven ts are of in terest in various technologies and industrial units like hi gh energy densi ty batteries, photo electro-chemical ce ll s, elec tr odeposition and wet electrolytic capacitors a nd in electro -o rgan ic synthes is. The physico-chemical be hav iour of liquid mixtures has been assessed by such studi es in our ea rli er works5' 11 . Viscosity, density and ultrasound speed measureme nt s and th e properties derived from these are exce ll e nt tools to detect so lute-so lute a nd solute-solve nt interactions. Such interactions have been st udi ed in H 2 0 and OM SO mixture by using a mi xture of CdCI 2 and KCI as so lu te . The density, viscosity and ultrasound speed of mixture of CdCl 2 and KCI electrolytes are expected to show completely different behav iour in OMSO and H 2 0 mixtures due to the probability of complex formation . Inte rmolec ular interactions lead to formation of bond between water and OMSO. Experimental Doubly di still ed water having a spec ifi c conductance of 2.4 x 10'6 ohm' l was co ll ected an d used. The va lue of ultraso und speed of conductiv it y water was found to be 1490.0 ms'l at 25 D C, wh i ch agrees well with th e literature va lu e l7 . DMSO (density 1. 10 xlO ,3 kgm,3 ) was used as such. The so luti ons of different concentrations of CdCl 2 an d KCI (bo th AnalaR) were prepared by weight d il utio n in OM SO- wa ter mi xt ur e as in a binary system and kept for two ho urs in a thermostat at th e studi ed temperatu res. Ultrasound speed was meas ur ed by us in g a s in gle cry stal inter fe rometer (model F-81 ) at 2 MH z. The accuracy of sound speed measurements was ± 0.03 o/c . A bicapi Il ary pyknometer mounted on temperature controlled water bath was us ed for dens it y meas ur eme nt s, the accuracy be in g ±0.050/0 . The temperature of the test system was maintained at ±O .I DC in a thermostatic water bath. Results and discussion The various acoustic parameters such as adiabatic compress ibility acous ti c impeda nce (Z) and solva tion number (Sn) have been calcu lated at variou s temperatures fro m 25 D C to 45 D C using ultrasound speed (U), density (p) a nd viscos ity (11 ) data of th e system according to following equ ati on s: = 1/ U 2p ... ( I ) Z = Up ... (2) Sn = (111/1/ 2) X - ... (3) where U, P are sound speed an d densi ty of solutions res pec ti ve ly, nl , n2 are the mol es of so lut es and so lv e nt respectively; and and are the adiabatic compressibility of so lution a nd solvent. respectively. Ultrasound speeds of cadmium ch loride (CdCl 2 ) and potassi um chloride ( KCI ) in bin ary solvc nt mixtures of dimethyl sulphox id e (OM SO) and water (H 2 0) have been measured with th e help of ultrasonic interferometer at 2MHz. Study of th e variation of ultraso nic ve loc it y of CdClr KCI at different concentrations and temperatures in coaqueous solvent of water and OMSO (l: 1 v/v) the variat ion to be non-linear. This indicates that there are strong interaction s in th e CdClrKCI-OMSO-f - hO system . Ultrasound speed is influenced by the density (p) and adiabatic compressibility Ws ). Th c variation of'