Simultaneous measurement of the density and viscosity of compressed liquid toluene

A vibrating-wire densimeter described previously has been used to perform simultaneous measurements of the density and viscosity of toluene at temperatures from 222 to 348 K and pressures up to 80 MPa. The density measurements are essentially based on the hydrostatic weighing principle, using a vibrating-wire device operated in forced mode of oscillation, as a sensor of the apparent weight of a cylindrical sinker immersed in the test fluid. The resonance characteristics for the transverse oscillations of the wire, which is also immersed in the fluid, are described by a rigorous theoretical model, which includes both the buoyancy and the hydrodynamic effects, owing to the presence of the fluid, on the wire motion. It is thus possible, from the working equations, to determine simultaneously, both the density and the viscosity of the fluid from the analysis of the resonance curve of the wire oscillation, the density being related essentially to the position of the maximum and the viscosity to its width. New results of measurements of the density and viscosity of toluene in the compressed liquid region are presented, and compared with literature data. The density results extend over a temperature range 222 K less than or equal to T less than or equal to 348 K, and pressures up to 80 MPa. The viscosity results cover a temperature range of 248 K less than or equal to T less than or equal to 348 K and pressures up to 80 MPa. The uncertainty of the present density data is estimated to be within +/-0.1% at temperatures 298 K less than or equal to T less than or equal to 350 K, and +/-0.15% at 222 K less than or equal to T less than or equal to 273 K. The corresponding overall uncertainty of the viscosity measurements is estimated to be +/-2% for temperatures 298 K less than or equal to T less than or equal to 350 K, and +/-3% for 248 K less than or equal to T less than or equal to 273 K.