Thermodynamic Properties of Gaseous Nitrous Oxide and Nitric Oxide From Speed-of-Sound Measurements

Published

October 16, 2008

Author(s)

John J. Hurly

Abstract

The speed of sound was measured in gaseous nitrous oxide (N2O) and nitric oxide (NO) using an acoustic resonance technique with a relative standard uncertainty of less than 0.01 %. The measurements span the temperature range 200 K to 460 K at pressures up to the lesser of 1.6 MPa or 80 % of the vapor pressure. The data were analyzed to obtain the constant-pressure ideal-gas heat capacity C as a function of temperature with a relative standard uncertainty of 0.1 %. For N2O, the values of C agree within 0.1 % with those determined from spectroscopic data. For NO, the values of C differ from the spectroscopic results by as much as 1.5 %, which is slightly more than the combined uncertainties. The speed-of-sound data were fitted by virial equations of state to obtain temperature-dependent density virial coefficients. Two virial coefficient models were employed, one based on square-well intermolecular potentials, and the second based on a hard-core Lennard-Jones intermolecular potential. The resulting virial equations reproduced nearly all the sound-speed data to within 0.01 % and may be used to calculate vapor densities with relative standard uncertainties of 0.1 % or less.

Citation

International Journal of Thermophysics

Pub Type

Journals

Keywords

Equation of state, ideal-gas heat capacity, intermolecular potential, N2O, nitric oxide, nitrous oxide, NO, speed of sound, thermodynamic properties

Citation

Hurly, J. (2008), Thermodynamic Properties of Gaseous Nitrous Oxide and Nitric Oxide From Speed-of-Sound Measurements, International Journal of Thermophysics (Accessed December 5, 2024)