Recommended Data for Vapor-Pressure

See TUPAC Recommended Data for Vapor Pressure Calibration ... 

Source "lUPAC Recommended Data for Vapor Pressure Calibration," in CRC Handbook of Chemistry and Physics (1913-1995), 75th Edition (Special Student Edition), editor-in-chief, David R. Lide, 6-109 (Boca Raton, FL CRC Press, 1994). 

See Vapor Pressure of Fluids at Temperatures below 300 K See TUPAC Recommended Data for Vapor Pressure Calibration ... 

Figure 7.16. Recommended values of net positive suction head (NPSH) at various temperatures or vapor pressures (a) NPSH of several types of pumps for handling water at various temperatures, (b) Correction of the cold water NPSH for vapor pressure. The maximum recommended correction is one-half of the cold water value. The line with arrows shows that for a liquid with 30 psia vapor pressure at 100°F, the reduction in NPSH is 2.3 ft (data erf Worthington International Inc.).

Any substance which may be obtained pure and for which accurate vapor pressure data are available may be used for vapor pressure thermometry. Stock recommended a convenient series of compounds and, in collaboration with Hen-nig and others, he obtained accurate vapor pressure data for these compounds.15 These data were obtained on a temperature scale for which 0°C = 273.1K however, more recent data on several of the compounds show it would be difficult to improve on Stock s vapor pressure tables. When high accuracy is desired, the usual precautions involved in precise manometry (Chapter 7) must be observed. 

The NIST s Thermodynamics Research Center (TRC) has a large collection of pure-fluid thermodynamic and transport properties tables of recommended values and correlations exist both in paper form and in a computer database [12], The TRC has also produced books with comprehensive compilations for organic compounds (sometimes also available as software) for vapor pressure [17], liquid density [18], and ideal-gas heat capacity [29], in addition to a compilation on virial coefficients [32]. Their major archival database of experimental pure-component and mixture data is called Source [97] it is currently available only to members of their consortium. Some data for mixtures of organic compounds are published in the periodical Selected Data on Mixtures [49]. More information is at http //trc.nist.gov. 

Estimation methods for the vapor pressure are still not reliable enough to apply them in process simulations for components whose behavior is decisive. Vapor pressure estimations can be used for components where the order of magnitude of the vapor pressure is sufficient (e.g., to decide whether the component occurs at the top or at the bottom of a column). Even in this case, it depends on the frequency it is used. For the simulation and optimization of a process for basic chemicals it is strongly recommended to have vapor pressure curves based on data points for all the components involved, whereas for the batch production of fine chemicals with a tight timef rame or during process evaluation an estimation might be acceptable. 

The procedure of Beutier and Renon as well as the later on described method of Edwards, Maurer, Newman and Prausnitz ( 3) is an extension of an earlier work by Edwards, Newman and Prausnitz ( ). Beutier and Renon restrict their procedure to ternary systems NH3-CO2-H2O, NH3-H2S-H2O and NH3-S02 H20 but it may be expected that it is also useful for the complete multisolute system built up with these substances. The concentration range should be limited to mole fractions of water xw 0.7 a temperature range from 0 to 100 °C is recommended. Equilibrium constants for chemical reactions 1 to 9 are taken from literature (cf. Appendix II). Henry s constants are assumed to be independent of pressure numerical values were determined from solubility data of pure gaseous electrolytes in water (cf. Appendix II). The vapor phase is considered to behave like an ideal gas. The fugacity of pure water is replaced by the vapor pressure. For any molecular or ionic species i, except for water, the activity is expressed on the scale of molality m ... 

Stull1 provides vapor pressure data up to the critical point for acetic acid and propionic acid Data on all tour compounds are available up to the boiling point. The vapor pressures up to the critical point were calculated by (he method recommended by Miller 1 and described in the Appendix. For acetic and propionic acid, this method gave an aver ugc error of 3.4 5 ... 

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