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Third Virial Coefficient for Air-Water Vapor Mixtures
R W Hyland1,2, E A Mason2
1Institute for Basic Standards, National Bureau of Standards, Washington, D.C. 20234.
Abstract:
The third interaction virial coefficient C for air-water vapor mixtures is estimated in the temperature range 0 to 100 °C, by means of an approximate method based on molecular association. The results are believed accurate to within a factor of two. The value of C can be combined with previous estimates of the other interaction coefficient C and the values of the third virial coefficients of pure air and pure water vapor, to give a quantitative description of the equation of state of air-water vapor mixtures through the complete third virial coefficient. It is shown that the maximum total contribution from both C and C to the compressibility factor is only of the order of parts in 104 up to 100 °C and 100 atmospheres total pressure. At -50 °C, it can be shown by extrapolation of C that the contribution of the C term to the compressibility factor is only on the order of parts in 1011.
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