The viscosity and density of n-dodecane and n-octadecane at pressures up to 200 MPa and temperatures up to 473 K

A vibrating-wire instrument for simultaneous measurement of the density and viscosity of liquids under conditions of high pressure is described. The instrument is capable of operation at temperatures between 298.15 and 473.15 K at pressures up to 200 MPa. Calibration was performed by means of measurements in vacuum, air, and toluene at 298.15 K. For n-dodecane measurements were made along eight isotherms between 298.15 and 473.15 at pressures up to 200 Pa, while for n-octadecane measurements were measured along seven isotherms between 323.15 and 473.15 at pressures up to 90 Pa. The estimated uncertainty of the results is 2% in viscosity and 0.2% in density. Comparisons with literature data are presented.