Saturation vapor pressure data

A pure fluid is completely characterized by the three molecular parameters, v r, and , and the scale factors T P, and p. P v /PP = 1 and Mir = v p = PP p /P. In principle, any thermodynamic property can be utilized to determine these parameters. Saturated vapor pressure data is useful as they are readily available for a variety of fluids. A compendium of such data is available for organic liquids. The lattice fluid theory of Sanchez and Lacombe as described is similar to the van der Waals EOS as discussed in the earlier section for small molecules. The virial form of the EOS of Sanchez and Lacombe can be written as follows ... 

An analytical method for the prediction of compressed liquid densities was proposed by Thomson et al. " The method requires the saturated liquid density at the temperature of interest, the critical temperature, the critical pressure, an acentric factor (preferably the one optimized for vapor pressure data), and the vapor pressure at the temperature of interest. All properties not known experimentally maybe estimated. Errors range from about 1 percent for hydrocarbons to 2 percent for nonhydrocarbons. 

The solvent s activity can be determined by measuring the saturation vapor pressure above the solution. Such measurements are rather tedious and their accuracy at concentrations below 0.1 to 0.5M is not high enough to produce reliable data therefore, this method is used only for concentrated solutions. The activity can also be determined from the freezing-point depression or boiling-point elevation of the solution. These temperature changes must be ascertained with an accuracy of about 0.0001 K, which is quite feasible. This method is used primarily for solutions with concentrations not higher than 1M. 

Thus, if the saturated vapor pressure is known at the azeotropic composition, the activity coefficient can be calculated. If the composition of the azeotrope is known, then the compositions and activity of the coefficients at the azeotrope can be substituted into the Wilson equation to determine the interaction parameters. For the 2-propanol-water system, the azeotropic composition of 2-propanol can be assumed to be at a mole fraction of 0.69 and temperature of 353.4 K at 1 atm. By combining Equation 4.93 with the Wilson equation for a binary system, set up two simultaneous equations and solve Au and A21. Vapor pressure data can be taken from Table 4.11 and the universal gas constant can be taken to be 8.3145 kJ-kmol 1-K 1. Then, using the values of molar volume in Table 4.12, calculate the interaction parameters for the Wilson equation and compare with the values in Table 4.12. 

De Pablo, R.S. (1976) Determination of saturated vapor pressure in range 10-1—10 torr by effusion method. J. Chem. Eng. Data 21, 141-143. 

The solution requires the concentration of the heptane and toluene in the vapor phase. Assuming that the composition of the liquid does not change as it evaporates (the quantity is large), the vapor composition is computed using standard vapor-liquid equilibrium calculations. Assuming that Raoult s and Dalton s laws apply to this system under these conditions, the vapor composition is determined directly from the saturation vapor pressures of the pure components. Himmelblau6 provided the following data at the specified temperature ... 

The most important data during main drying is the temperature at the moving sublimation front which cannot be measured by Ths or RTDs. In 1958, Neumann and Oetjen 11.651 showed that the barometric temperature measurement (BTM) measures exactly this data. In Fig. 1.77 this is schematically shown if the drying chamber is separated from the condenser by a valve for a short time the pressure in the chamber rises to the saturation vapor pressure (ps) corresponding to the temperature of the sublimation front. ps can be converted into the ice temperature by the water vapor- temperature diagram (e. g. 0.3 mbar = -30 °C). Data for accurate conversion are given in Table 1.11 the temperatures between -100 and -1 °C. 

Although calorimetric methods are usually regarded as yielding the most accurate enthalpies of vaporization [39], the measurement of the saturation vapor pressures of a liquid as a function of temperature is also widely used for the same purpose and may afford good quality data. Among these so-called vapor pressure methods [35], differential ebulliometry is probably one of the most reliable. Briefly, the ebulliometric method consists in measuring the boiling temperatures of a liquid at different pressures. In the differential set-up, the pressure over the... 

The calculation of compressibility factors of gaseous ethanol can be made with equation 2.18, because the second virial coefficient (B) is available at different temperatures [20] and the saturation vapor pressures can be interpolated or extrapolated from the experimental data (figure 2.4). One obtains Z = 0.991 at... 

Since the product Dp is independent of pressure, the evaporation rate is essentially independent of pressure. There is a mild effect of pressure on the transfer number, as will be discussed in more detail when the droplet burning case is considered. In order to find a solution for Eq. (6.87) or, more rightly, to evaluate the transfer number B, mAs must be determined. A reasonable assumption would be that the gas surrounding the droplet surface is saturated at the surface temperature Ts. Since vapor pressure data are available, the problem then is to determine Ts. 

Rohac, V., Ruzicka, V., and Ruzicka, K. Measurements of saturated vapor pressure above the liquid phase for isomeric dichlorobenzenes and 1,2,4-trichlorobenzene, J. Chem. Eng. Data, 43(5) 770-775, 1998. 

To construct the adsorption isotherm, the adsorption, desorption, and calibration cycle shown in Fig. 15.11 is repeated for each data point required. Errors are not cumulative since each point is independently determined. Relative pressures corresponding to each data point are established by measuring the saturated vapor pressure using any of the preceding methods or by adding 15 torrs to ambient pressure. Thus, if X is the mole fraction of adsorbate in the flow stream, the relative pressure is given by... 

The above procedure is now applied to two ethanol-water (8, 9) and five 1-propanol-water systems (9) which have been saturated with an inorganic salt and which show partial miscibility. The vapor pressures and molar volumes (10), and second virial coefficients of water (11), ethanol (12), and 1-propanol (IS) were obtained by interpolation of literature data. The vapor pressures of water saturated with salts over a temperature range are available for all salts (14) except lead nitrate. Such data are unavailable for both alcohols saturated with salt. Hence a correction to the saturation vapor pressure is made by multiplying by the ratio of the vapor pressure of alcohol saturated with salts to the vapor pressure... 

F is the equilibrium particle phase concentration of a compound (ng/m3) TSP is the concentration of total suspended particles ( tg/m3) cg is the equilibrium gas phase concentration and Cp is the concentration within the particle phase of the compound (ng/m3). In essence Kp is the ratio of the fractional concentration of a given organic compound on particles to its concentration in the gas phase. Within a given class of organic compounds, and in some cases even among different classes, experimental data shows that the logarithm of Kp tends to correlate in a linear fashion with the log of the saturation vapor pressure. Using Equation 2.2... 

Aim, K. (1994) Saturated vapor pressure measurements on isomeric mononitrotoluenes at temperatures between 380 and 460 K. J. Chem. Eng. Data 39, 591-594. 

VL(L) E measurements for binaries involving water with alcohol and acid have been done, as described elsewhere [2]. Figure 8.6 presents experimental vapor pressure data for 2-ethylhexyl laurate. The normal boiling point (nbp) is 607.6 K, close to the prediction by Gani s method. On the other hand, the prediction of the whole saturation curve by Riedel s method (noted estimation in Figure 8.6) is in large error at lower pressures. This fact can affect the accuracy of chemical equilibrium calculation, but fortunately the errors compensate each other [2]. 

Eq. (13-4). Otherwise is evaluated from vapor pressure data with a Poynting saturated-vapor fugacity correction. When the total pressure is less than about 202.6 kPa (2 atm) and all components in the mixture have a critical temperature that is greater than the system temperature, then Of =Pf /P and Of = 1.0. Equation (13-4) then reduces to... 

These differences in the polymer films also show up in differences in the sign of the frequency response. The polyimide used to generate the data in Figure 4.7 exhibits a positive frequency response when challenged with relatively low concentrations (ptpo <0.1, where po is the saturation vapor pressure) of the various species tested. The other two SAW studies, however, report negative frequency responses to the vapor challenges. The positive response shown in Figure 4.7... 

Figure 4.17 Frequency shift as a function of time measured for a gold-coated SAW device exposed to an Na gas stream containing CH3(CH2)isSH at tproximately 25% of its saturation vapor pressure. Leveling of the frequency shift at approximately 1.15 monolayers indicates that the polycrystalline gold Him has a roughness factor of 1.15. The kinetic data fit a simple, first-order Langmuir rate law. (Reprinted with permission. See Ref. [143J. 1991 American Chemical Society.)...

Pesticides applied indoors vaporize from treated surfaces (e.g. carpets and baseboards) and can be resuspended into air on particles. Many pesticides are semivolatile (saturation vapor pressures between 10 kPa and 10 kPa at 25 °C) and tend to vaporize from treated indoor surfaces. The rate of volatilization will depend on the vapor pressure of the compound, the formulation (solvent, surfactants, microencapsulation, etc.), the ambient and surface temperatures, indoor air movement and exchange rates (ventilation), the type of surface treated and the elapsed time after application. The vapor pressure data for pure pesticides is frequently available and may be of value for assessing the relative importance... 

As calculated from molar ion concentration data using the model in this study, e is the saturated vapor pressure in millibars at 25°C. 

Measured values interpolated from graphically presented data giving vapor pressure lowering at 25°C as a function of brine density (31), e g is the saturated vapor pressure of the brine in millibars at 25°C. 

The model was shown to predict osmotic coefficients to within the experimental error for the determination of osmotic coefficients from saturated vapor pressure measurements. Activity coefficient calculations appeared to be consistent with the available data for mixed electrolyte solutions. 

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