Physical properties of pyridinium ionic liquids

► Physical properties, such as density, dynamic viscosity and surface tension of pyridinium ionic liquids were determined. ► The experimental data for all measured physical properties of pyridinium ILs were expressed by empirical equations. ► Entropy and enthalpy of surface formation per unit surface area of pyridinium ILs have been calculated. ► Thermal stability of pyridinium ILs was determined.