Volumetric and acoustic study of aqueous binary mixtures of quinine hydrochloride,guanidine hydrochloride and quinic acid at different temperatures

In the present communication, we report the fundamental thermodynamic properties like volumetric and compressibility of very important bioactive compounds, viz. quinine hydrochloride, guanidine hydrochloride and quinic acid (0.01 to 0.1) mol · kg⁻¹ in water at temperatures T = (278.15, 288.15 and 298.15) K. The experimental values of density (ρ) of aqueous solutions and speed of sound (u) in aqueous solutions of the above compounds within the concentration range (0.01 to 0.1) mol · kg⁻¹ have been obtained. The apparent molar volumes (V_ϕ), and apparent molar isentropic compressibilities (κ_ϕ) of quinine hydrochloride, guanidine hydrochloride and quinic acid in water have been computed at three different temperatures. Speed of sound values have also been used to calculate the hydration number (n_H) of the solute. The temperature dependence of the apparent molar volume has been used to calculate the thermal expansion coefficient (α¹), apparent molar expansivity $(E_{\varphi }^0)$ and Hepler’s constant $\left({\partial }^2{V}_{\varphi }^0/\partial T^2\right)$. The derived parameters have been used to interpret the results in terms of (solute + solute)/(ion + ion), (solute + solvent) interactions, structure making and structure breaking tendencies of solutes in water.