Third virial coefficient for air-water vapor mixtures

The third interaction virial coefficient Caww for a ir-water vapor mixtures is estimated in the temperature range 0 to 100 °C, by mea ns of an approximate me thod based on molec ular assoc iation .The res ult s are beli eved accurate to within a fac tor of two.The value of CawlV ca n be combined with prev ious es timates of th e other interaction coefficient C",m and the values of the third virial coefficient s of pure air and pure water vapor, to give a quantitative description of the equation of s tate of air-water vapor mixtures through th e complete third vi rial coefficient.It is shown that the maximum total contribution from both CawlV and Caaw to the compress ibilit y factor is o nly of the order of parts in 10' up to 100 °C and 100 atmospheres total press ure .At -50°C, it can be shown by extrapolation of Caww that the co ntribution of th e Caww term to the co mpressi bility fac tor is on ly on the order of parts in 1011 .