Ultrasonic, volumetric and viscometric studies of lactose in mixed solvent of DMF-H2O at 298, 308 and 318 K

Acoustic parameters are useful to understand the effect of temperature on the interactions of lactose in mixed solvent of (DMF-H2O). Density (rho), viscosity (eta), sound speed (u) and refractive index (n(D)) of lactose with mixed solvent of N,N-dimethylformamide-water or (DMF-H2O) from 0.1050 to 1.045 m at different temperatures have been determined using bicapillary pycnometer, Ostwald's viscometer, Abbe's refractometer and single frequency ultrasonic interferometer at 2 MHz frequency respectively. The derived parameters like apparent molal volume (phi(v)), free volume (V-f), intermolecular free length (L-f), acoustic relaxation time (tau), Gibb's free energy (Delta G), internal pressure (pi(i)), Rao's constant (R-m), Wada's constant (W), adiabatic compressibility (beta), acoustic impedance (Z), absorption coefficient (alpha/f(2)) and molar refractivity (R-D) have been determined from experimental data. All the measurements have been carried out in a refrigerated water bath with circulating medium having an uncertainty of +/- 0.1 degrees C. Positive values of the Jones-Dole coefficient (B) indicate structure making tendency. The solute-solvent interactions are stronger at all the temperatures taken for the study. (C) 2013 Production and hosting by Elsevier B.V. on behalf of King Saud University.