Pressure, critical table

Various methods are available for estimation of the normal boiling point of organic compounds. Lyman et al. review and give calcula-tional procedures for the methods of Meissner, Miller, and Lydersen/ Forman-Thodos. A more recent method that has been determined to be more accurate is the method of Pailhes, which reqmres one experimental vapor pressure point and Lydersen group contributions for critical temperature and critical pressure (Table 2-385). 

Other Mixtures of Closely Related Compounds.—It does not follow, however, that it is only when the critical pressures are equal that the formula is applicable, and it will be seen from Table 6 (p. 40) that the deviations may be exceedingly small when the liquids are closely related, but their critical pressures (Table 5) are widely different (12). 

Tj. is the reduced temperature, T is the critical temperature, is the critical pressure, and is the modified Rackett parameter as given in the supplemental table for pure-component properties. 

The most common mobile phase for supercritical fluid chromatography is CO2. Its low critical temperature, 31 °C, and critical pressure, 72.9 atm, are relatively easy to achieve and maintain. Although supercritical CO2 is a good solvent for nonpolar organics, it is less useful for polar solutes. The addition of an organic modifier, such as methanol, improves the mobile phase s elution strength. Other common mobile phases and their critical temperatures and pressures are listed in Table 12.7. 

Properties. Tetrafluoroethylene (mol wt 100.02) is a colorless, tasteless, odorless, nontoxic gas (Table 1). It is stored as a Hquid vapor pressure at —20° C = 1 MPa (9.9 atm). It is usually polymerized above its critical temperature and below its critical pressure. The polymerization reaction is highly exothermic. 

Be is the critical pressure, MPa. Values of Ap from Table 2-383 are summed for each part of the molecule to yield X Ap. Calculation of the Platt number is discussed under Critical Temperature. Errors in average 0.07 MPa and are less reliable for compounds with 12 or more carbon atoms. 

Kn, = Valve recovery coefficient (see Table 3) r, = Critical pressure ratio (see Figures 1 and 2)... 

Table 1 gives critical pressures for miscellaneous fluids. Table 2 gives relative flow capacities of various... 

For any given pressure up to the critical pressure (the pressure at which water and steam have the same specific weight and there is no separation in phase), there is a corresponding boiling point, and these correlations are given in commonly available steam tables. 

Chueh s method for calculating partial molar volumes is readily generalized to liquid mixtures containing more than two components. Required parameters are and flb (see Table II), the acentric factor, the critical temperature and critical pressure for each component, and a characteristic binary constant ktj (see Table I) for each possible unlike pair in the mixture. At present, this method is restricted to saturated liquid solutions for very precise work in high-pressure thermodynamics, it is also necessary to know how partial molar volumes vary with pressure at constant temperature and composition. An extension of Chueh s treatment may eventually provide estimates of partial compressibilities, but in view of the many uncertainties in our present knowledge of high-pressure phase equilibria, such an extension is not likely to be of major importance for some time. 

Every gas has a critical temperature above which it caimot be liquefied by the application of pressure alone. The critical pressure is that required to liquefy a gas at its critical temperature. Data for common gases are given in Table 4.5. As a consequence ... 

Table 1-5 gives critical pressures for miscellaneous fluids. Table 1-6 gives relative flow capacities of various types of control valves. This is a rough guide to use in lieu of manufacturer s data. 

Table 10-4 Critical Pressure of Various Fluids, psia...

Critical points vary widely. Table 6.1 shows a representative sample of critical parameters and it is immediately obvious why carbon dioxide is widely used. With a critical temperature just above room temperature and a critical pressure that is relatively low, the amount of energy needed to render carbon dioxide supercritical is comparatively small. Fluoroform (CHF3) and difluoromethane also have easily attainable critical parameters, but they are much more expensive than carbon dioxide. Despite its high critical temperature and pressure, supercritical water (SCH2O) is used widely as a destructive medium since it is highly acidic. 

Thus, it would appear that overpressures experienced in the air from LNG RPTs for spills less than about 30 are not particularly large unless one is very close to the spill site. Overpressures in the water are much larger, as shown in Table X from transducer measurements about 0.7 m from the surface. In fact, in one instance, the overpressure in the water exceeded the critical pressure of the LNG this would not have been expected from the superheated liquid model. 

K, there is a significant increase in pressure and values of 30 bar (or higher) were recorded. Assuming that the water-R-22 interface temperature had to attain the superheat-limit value before an explosion occurred, these data are in remarkable agreement with in Table XVI. Also shown in Fig. 11 is the vapor pressure of R-22 calculated for the interface temperature between the water and the saturated R-22 (232 K). Essentially all measured pressures fall below this curve, and this suggests that the maximum pressure transient corresponds to the vapor pressure determined in this manner. (Another limit could be chosen as the critical pressure of R-22, 50 bars, but this value significantly exceeds any measured pressure.)... 

Table 9.3 Critical temperatures (TJ and critical pressures (P ) for gaseous species of geochemical interest (from Garrels and Christ, 1965).

Values of critical temperature and critical pressure for gaseous species of geochemical interest are listed in table 9.3. 

Under the required conditions, 300 atm and 600 K, the reactants will show non-ideal behaviour and to obtain values of 7 from Newton s charts [12], the critical pressures and temperatures of the products and reactants are needed. These are listed in Table 8, together with the reduced pressures and temperatures corresponding to the equilibrium conditions. 

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