Vapor pressure empirical Antoine equation

Theoretically based correlations (or semitheoretical extensions of them), rooted in thermodynamics or other fundamentals are ordinarily preferred. However, rigorous theoretical understanding of real systems is far from complete, and purely empirical correlations typically have strict limits on apphcabihty. Many correlations result from curve-fitting the desired parameter to an appropriate independent variable. Some fitting exercises are rooted in theory, eg, Antoine s equation for vapor pressure others can be described as being semitheoretical. These distinctions usually do not refer to adherence to the observations of natural systems, but rather to the agreement in form to mathematical models of idealized systems. The advent of readily available computers has revolutionized the development and use of correlation techniques (see Chemometrics Computer technology Dimensional analysis). 

The equation developed by the Design Institute for Physical Property Data (DIPPR) is another successful correlating tool for vapor pressure (4). It is an empirical extension of the Antoine equation and has two additional constants, D and E ... 

This can be empirically modified by introducing additional parameters to give the three-parameter Antoine equation by replacing T with (T + C), where C is a constant, which is the most common vapor pressure correlation used to represent experimental data (Zwolinski and Wilhoit 1971, Boublik et al. 1984, Stephenson and Malanowski 1987, and other handbooks). 

The Antoine equation is the most commonly used empirical equation for describing the vapor pressure of a liquid as a function of temperature. 

Many empirical expressions have been proposed to represent the temperature dependence of the vapor—liquid saturation pressure, as shown by the vaporization curve of Figure 2. The most popular is the Antoine equation ... 

The vapor pressure of a chemical substance increases rapidly with temperature. Many equations have described this temperature dependence so that the vapor pressure can be calculated for a temperature of interest. The Antoine (1888) equation is most familiar. Riddick, Bunger, and Sakano (1996) provide an extensive discussion of many of the empirical equations used to describe the temperature dependence of the vapor pressure. To apply a particular equation to a chemical, the necessary parameters must be available from experimental data. If no such information exists, some method is needed to estimate the parameters. 

The vapor pressure of pure n-alkanes can be readily calculated using an empirical formula based on the Antoine equation in Eq. (4-93) (Piringer, 1993) ... 

A relatively simple empirical equation that correlates vapor pressure-temperature data extremely well is the Antoine equation... 

Equation (3.31) is derived from the Clausius-Clapeyron equation (see Chap. 4). Empirical correlations of vapor pressure are frequently given in the form of the Antoine equation (refer to Appendix G for values of the constants) ... 

The most frequently used equations that relate the vapor pressure of a material to temperature are as follows. In moderate temperature ranges, the Antoine equation provides a reasonable empirical prediction, given by... 

With an additional parameter C, the Antoine eqnation is widely used for vapor pressure data up to about 2 bars. Over the entire temperature range, an eqnation of greater complexity is required. Several have been obtained by integrating Equation (4.454) based on varions temperature functions for A h and A,v and empirical observation. The Frost-Karkwarf-Thodos eqnation [1-3] is widely nsed with constants reported [4] for a large number of substances. The eqnation is... 

During the past century many empirical mathematical functions have been used to relate vapor pressure to temperature most are modifications of Eq. (1.7). These functions have several parameters that are characteristic of the compound. Curve fits off experimental data, usually by minimizing the sum of the squares of the deviations between the calculated and observed pressures or temperatures (least squares criterion), provide these parameters. The first and most widely used of these equations is the Antoine equation [1888-ant, 46-tho]. The original form is,... 

Alternatively, vapor pressure may be estimated from any of a large number of empirical correlations. Although not the most accurate over a wide range of temperature, the Antoine equation is convenient and widely used. The reduced pressure form of the Antoine equation is... 

The Antoine equation is an empirical relationship between vapor pressure and temperature with three fitted parameters—Aa,Ba,Ca-... 

At the vapor-liquid boundary, a single-phase system splits into two phases,i each with its own properties (molar volume, enthalpy, entropy, etc.). The precise conditions under which phase splitting occurs is an important problem in thermodynamics. Up to this point we have relied on tabulated values and empirical equations, such as the Antoine equation, to establish the relationship between saturation temperature and pressure. In this chapter we develop a connection between the conditions at saturation and the equation of state. The key thermodynamic property that makes this connection possible is the Gibbs energy. 

Th is concentration, expressed as a fraction, essentia lly is the solvent vapor pressure divided by 750Torr (mm Hg). The solvent vapor pressure can be calculated from the Antoine Equation using empirical constants which can be found in... 

More complex vapor-pressure equations are empirical, with littie if any theoretical basis. They mostly start with the C-C equation and add or modify terms to make their equation fit the experimental data more accurately than the C-C equation. The most widely used of these is the Antoine equation, which adds one arbitrary correction constant to the C-C equation, thus modestly increasing its complexity and vastly improving its ability to fit experimental data. 

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