Viscosity and speed of sound of gaseous nitrous oxide and nitrogen trifluoride measured with a greenspan viscometer

The viscosity and speed of sound of gaseous nitrous oxide and nitrogen trifluoride were measured using a Greenspan acoustic viscometer. The data span the temperature range 225-375 K and extend up to 3.4 MPa. The average relative uncertainty of the viscosity is 0.68% for N2O and 1.02% for NF3. The largest relative uncertainties were 3.09 and 1.08%, respectively. These occurred at the highest densities (1702 mol.m(-3) for N2O and 2770 mol.m(-3) for NF3). The major contributor to these uncertainties was the uncertainty of the thermal conductivity. The speeds of sound measured up to 3.4 MPa are fitted by a virial equation of state that predicts gas densities within the uncertainties of the equations of states available in the literature. Accurate measurements of the speed of sound in both N2O and NF3 have been previously reported up to 1.5 MPa. The current measurements agree with these values with maximum relative standard deviations of 0.025% for N2O and 0.04% for NF3.