Vapor pressure equations for

Vapor Density. Substitution of the Antoine vapor-pressure equation for its equivaient iog P in the ideai gas equation gives... 

Ac, Be, Cc Constants of the Antoine vapor pressure equation for the liquid state from Tr = 0.75 (or a higher TB as indicated) to the critical temperature. See method of obtaining the constants on page 7. 

The introduction of a third constant C leads to an improved equation which has been tested in some detail and found to be the best three-parameter vapor pressure equation for general use.1-2 Usually the temperature term in Eq. (4) is in degrees Celsius. Because of its simple form and generally good accuracy, this equation has been chosen for use in some of the most extensive compilations of... 

From Equations 1 and 2, the phase equilibria depend upon knowing the pure component vapor pressures P 0, liquid phase activity coefficients ji and imperfection-pressure coefficients ft. The computer program which has been developed uses any of four different vapor pressure equations for providing Pi°. It uses the modified van Laar Equations (5) to give liquid phase activity coefficients and a Modified van der Waals Equation of State (4,6) to give imperfection-pressure coefficients ft. 

The molar absorptivities for PrBrs and Prig vapor were determined from Shimazaki and Niwas (22) vapor pressure equations for the solids and the extrapolations used in the earlier gaseous NdBrs and Ndls study. The heat capacities and heats of fusion for PrBrs and Pris were taken from Dworkin and Bredig s 7, S) data. The vapor pressure equations obtained for solid and liquid PrBrs are given by Equations 5 and 6 respectively... 

Phase equilibria of vaporization, sublimation, melting, extraction, adsorption, etc. can also be represented by the methods of this section within the accuracy of the expressions for the chemical potentials. One simply treats the phase transition as if it were an equilibrium reaction step and enlarges the list of species so that each member has a designated phase. Thus, if Ai and A2 denote liquid and gaseous species i, respectively, the vaporization of Ai can be represented stoichiometrically as —Aj + A2 = 0 then Eq. (2.3-17) provides a vapor pressure equation for species i. The same can be done for fusion and sublimation equilibria and for solubilities in ideal solutions. 

Ruff et al. (2) reported the melting point as 383 K. Cady and Hargreaves (2) calculated the melting point as 378 K, and the heat of fusion as 2.26 kcal mol" from vapor pressure equations for the crystal and liquid. This 2nd law value of A,.. H , when... 

Ruff et al. (3) reported the boiling point of WOF (i) as 459 K. and the heat of vaporization as 14.23 kcal mol" from the vapor pressure equation for the liquid. This 2nd law value of when corrected for aC of vaporization, is in good agreement with the value adopted in the tabulation. 

Huang, Y.H., and Chen G.B. (2006) A practical vapor pressure equation for helium-3 from 0.01 Kto the critical point. Cryogenics 46, 833-839. 

Values of Coefficients in the Vapor Pressure Equations for Helium... 

This table gives the electrical conductivity of highly purified water over a range of temperature and pressure. The first column of conductivity data refers to water at its own vapor pressure. Equations for calculating the conductivity at any temperature and pressure may be found in the reference. 

Critical Properties and Vapor pressure Equation for Alkanes CJIzn+i Normal Alkanes with n< 36 and Isomers for n = 4-w = 8 Literature values have been compiled and reviewed and predicting equations evaluated. 

The vapor pressure equation for the alpha phase is derived by evaluating free energy functions for the solid and the gas at 25 K intervals from 1000 to 1750 K and the transition temperature. For the liquid phase, values are evaluated at 50 K intervals from 1800 to 3600 K and the melting point. For the beta phase, values were evaluated at the transition and melting point temperatures and fitted to the Clausius-Clapeyron equation (Table 15). 

The vapor pressure equation for the beta phase was evaluated at 25 K intervals from 900 to 1550 K and the transition temperature and for the liquid phase at 50 K intervals from 1650 to 3500 K and the melting point. The constants for the gamma phase was obtained by calculating the vapor pressure values at the transition temperature, the melting point, and 1600 K (Table 119). 

Vapor pressure data for water are given in Problem 8.D10. For small ranges in tenperature, these data can be fit to an Antoine equation form with C = 273.16. The vapor pressure equation for 1-octanol is in Problem 8.D11. 

For this purpose, the values obtained from the vapor pressure equations for both components are multiplied with a factor which is specific for each dataset If the Antoine equation is used, this can be achieved by simply changing the parameter A in Eq. 3.30. The solid line in Figure F.8 shows that the correct slope of the bubble point line can be represented. The water activity coefficient at infinite... 

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