NIST Authors in **Bold**

Author(s): | John J. Hurly; Dana R. Defibaugh; Michael R. Moldover; |
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Title: | Thermodynamic Properties of Sulfur Hexafluoride |

Published: | May 01, 2000 |

Abstract: | We present new vapor phase speed-of-sound data u(P,T), new Burnett density-pressure-temperature data ρ(P,T), and a few vapor pressure measurements for sulfur hexafluoride (SF_{6}). The speed-of-sound data spanned the temperature range 230 K {less than or equal to} T {less than or equal to} 460 K and reached maximum pressures that were the lesser of 1.5 MPa or 80% of the vapor pressure of SF_{6}. The Burnett ρ(P,T) data were obtained on isochores spanning the density range 137 mol . m^{-3} {less than or equal to} ρ {less than or equal to} 4380 mol . m^-3^ and the temperature range 283 K {less than or equal to} T {less than or equal to} 393 K. (The corresponding pressure range is 0.3 MPa {less than or equal to} P {less than or equal to} 9.0 MPa.) The u(P,T) data below 1.5 MPa were correlated using a model hard-core, Lennard-Jones intermolecular potential for the second and third virial coefficients and a polynomial for the perfect gas heat capacity. The resulting equation of state has very high accuracy at low densities; it is useful for calibrating mass flow controllers and may be extrapolated to 1000 K. The new u(P,T) data and the new ρ(P,T) data were simultaneously correlated with a virial equation of state containing four terms with the temperature dependencies of model square-well potentials. This correlation extends nearly to the critical density and may help resolve contradictions among data sets from the literature. |

Citation: | International Journal of Thermophysics |

Volume: | 21 |

Issue: | No. 3 |

Keywords: | Burnett,equation-of-state,heat capacity,intermolecular potential,SF_{6},speed-of-sound,sulfur hexafluoride,thermodynamic properties,vapor pressure |

Research Areas: |