Ultrasonic studies on paracetamol in aqueous solutions of sodium salicylate and nicotinamide

Solubility enhancement of poorly soluble drug, paracetamol using hydrotropic agents like sodium salicylate and nicotinamide has been studied. In the present investigation, 1, 2, 3 and 4M of both sodium salicylate and nicotinamide are employed to enhance the solubility of poorly soluble paracetamol to study its different physico-chemical properties at 298.15, 303.15, 308.15 and 313.15 K. The values of density (d) and sound velocity (U) have been measured in aqueous paracetamol and paracetamol + aqueous solutions of sodium salicylate and nicotinamide separately in five different concentrations. Densities of these solutions were measured at the above said four temperatures but the ultrasonic velocities (U) have been measured at 298.15 K only. Experimental density data have been used to estimate various important parameters, such as apparent molar volume (Vɸ), limiting apparent molar volume (Vɸ0), apparent molar expansibility (Eɸ) and limiting apparent molar expansibility (Eɸ0). Further, from the ultrasonic data, different thermo-acoustical parameters, such as isentropic compressibility (Ks), apparent molar isentropic compressibility (Ks, ɸ), acoustic impedance (Z), molar compressibility (W), free volume (Vf), internal pressure (πi), molar sound velocity (R) and relative association (RA) have been evaluated and discussed in the light of solute-solute and solute-solvent interactions.