Table of Vapor Pressures

From a table of vapor pressure, this corresponds to a dew point of 61.8 F. 

Vapor pressure data are important in the identification, separation, and general manipulation of known compounds on the vacuum line and for the characterization of new compounds. This appendix was prepared with these applications in mind. It is introduced with a discussion of the use and limitations of several analytical expressions for the representation of vapor pressure data. A description of a least-squares treatment of vapor pressure data for fitting to the Antoine equation is then presented. Finally, a table of vapor pressures at convenient slush bath temperatures is presented for 479 compounds. 

In this chapter we get to know the second essential equation of surface science — the Kelvin5 equation. Like the Young-Laplace equation it is based on thermodynamic principles and does not refer to a special material or special conditions. The subject of the Kelvin equation is the vapor pressure of a liquid. Tables of vapor pressures for various liquids and different temperatures can be found in common textbooks or handbooks of physical chemistry. These vapor pressures are reported for vapors which are in thermodynamic equilibrium with liquids having planar surfaces. When the liquid surface is curved, the vapor pressure changes. The vapor pressure of a drop is higher than that of a flat, planar surface. In a bubble the vapor pressure is reduced. The Kelvin equation tells us how the vapor pressure depends on the curvature of the liquid. 

In the table of vapor pressure, there are values for the acentric factor CO, which is ... 

The pressure of water vapor in the air may be determined by cooling the air and observing the temperature at which condensation takes place. Thus, if condensation begins at 10°, the pressure of the water vapor in the air is 9.2 mm. but if condensation begins at 20°, the pressure must be 17.4 mm. The temperature at which condensation takes place is called the dew point. By observing the dew point and referring to a table of vapor pressures at different temperatures, the concentration or pressure of the water vapor in the air may be found. 

Referring to the table of vapor pressures of water on page 542, (6) record the vapor pressure for the dew point which you have found and for the temperature of the air. (7) What relation has the first value to the pressure of the water vapor actually existing in the air (8) What is the maximum pressure of water vapor possible in the air at the existing tern-... 

Comprehensive tables of vapor-pressure data of common liquids, such as water, common refrigerants, and others, may be found in Refs. [2,3]. For most liquids, the vapor-pressure data are obtained at a few discrete temperatures, and it might frequently be necessary to interpolate between or extrapolate beyond these measurement points. At a constant pressure, the Clausius-Clapeyron equation relates the slope of the vapor pressure-temperature curve to the latent heat of vaporization through the relation... 

This is handy, since extensive tables of vapor pressures are available (e.g., Boubliketal.. 1984 Dean. 1985 Green and Perry. 20081. Vapor pressure is often correlated in terms of the Antoine equation... 

You know that the total pressure is 755 torr. Your first task is to reference a table of vapor pressures of water versus temperature. (You can find such a table in a variety of places, such as the Chemical Rubber Company (CRC) Handbook.) After looking at the table, you determine that the partial pressure of water at 20 degrees Celsius is 17.5 torr. Now you re ready to calculate the pressure of the oxygen ... 

Calculate the approximate boiling point of a mixture of bromobenzene and water at atmospheric pressure. A table of vapor pressures of water and bromobenzene at various temperatures is given. 

The temperature dependence of many properties of methanol has been described in figures, tables, and equations. Plots of vapor pressure, liquid density, liquid heat capacity, vapor heat capacity, heat of vaporization, surface tension, liquid thermal conductivity, vapor thermal conductivity, liquid viscosity, and vapor viscosity against temperature have been given by Yaws [13] and by Flick [14]. Tables of vapor pressure [3,1517], liquid density [3,15,17], liquid volume [16], vapor density [15,17], vapor volume [16], liquid viscosity [15,18], vapor viscosity [15], surface tension [15,19], liquid heat capacity [15,17,20], vapor heat capacity [3,15,17], solid heat capacity [11], liquid thermal conductivity [15,17], vapor thermal conductivity [15], second viral coefficient [16], dielectric constant [21], refractive index [3], and heat of vaporization [16] have also been published. Thermodynamic properties of methanol in the condensed phases have been tabulated by Wilhoit et al. [11], and those in the gas phase have been given by Chao et aL [9]. 

Figure 4 presents a comparison of the test results to curves drawn from the published density values of Mathias [3] and Baly andDonnan [1], The curves from Mathias and Baly and Donnan were converted from density as a function of temperature to density as a function of vapor pressure according to the tables of vapor pressure versus temperature published in the Tables of Thermal Properties of Gases [4] by the National Bureau of Standards. The difference in density between Baly and Donnan and the test results obtained is about 0.3. It is believed that the difference is due mainly to the effects of temperature stratification, since it was shown that the effect of vapor bubbles was negligible. This shows that the curve prepared from the published values of density by Mathias or Baly and Donnan would have been satisfactory for the test tank in most applications. However, the observation that the liquid level dropped further due to pressurization in test 7, when the liquid was in the dome, than during test 8, when the liquid level was in the cylindrical portion, indicates that the depth beneath the surface at which the bubble formation begins is a function of the liquid surface area available for evaporation. 

Many handbooks have tables of vapor pressures, as do more detailed tables like the steam tables [1—4]. The values shown there are not direct experimental measurements. Instead, they are computed from equations that have been fitted to the experimental data. In the computer age we wish to represent the experimental data by equations that our computers can manipulate. There are some strong limits on the forms those equations can take, which we will see in Section 5.4. 

The subject of the Kelvin equation is the vapor pressure of a liquid. Tables of vapor pressures for various liquids and different temperatures can be found in common... 

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