Volumetric and viscometric studies of some drugs in aqueous solutions at different temperatures

Highlights: ► Study of aqueous solutions of biologically important compounds has been reported. ► MH is used for treating type II diabetes, RH is in treatment of peptic ulcer and TH is used to treat severe pain. ► All the compounds act as structure makers by volumetric studies. ► MH and RH act as weak structure breakers and TH acts as a weak structure maker by viscometric studies. - Abstract: Density and viscosity measurements are reported for aqueous solutions of the drugs like Metformin hydrochloride (MH), Ranitidine hydrochloride (RH) and Tramadol hydrochloride (TH) at different temperatures T = (288.15, 298.15, and 308.15) K within the concentration range (0 to 0.15) mol · kg−1. The density and viscosity data are used to obtain apparent molar volume of solute (φV) and relative viscosity (ηr) of aqueous solutions at different temperatures. The limiting apparent molar volume of solute (φV0), limiting apparent molar expansivity (φE0), thermal expansion coefficient (α∗), hydration number (nh), Jones–Dole equation viscosity A and B coefficients, experimental slope (SV) at different temperatures, and temperature coefficient of Bi.e.(dB/dT) at T = 298.15 K were also obtained. The results obtained have been interpreted in terms of solute–solvent and solute–solute interactions and structure making/breaking ability of solute in the aqueous solution.