Volume, apparent molar critical

The ratio of properties in Equation 9.24 is called the Krichevskii function, and identified at the solvent critical point as the Krichevskii parameter (Levelt Sengers 1991). The first EST correlation for partial molar volumes of gases in liquids was done by Brelvi (Brelvi and O Connell 1975c), using characteristic properties for his correlation of the reduced bulk modulus (Brelvi and O Connell 1972). Recent work (Ellegaard, Abildskov, and O Connell 2011) has used the form of Equation 9.4 for partial molar volumes of gases in ILs. The comparisons with data for these systems seem not to be as successful as for their compressibilities and phase equilibria, for reasons that are not apparent. 

Carboxylic Acids. Barton and Hsu measured the molar volumes of both formic and acetic acids at 50, 65, 95,110, and 125 C, at various pressures. They noted that, contrary to the simplest theory, the association constants for dimer formation were not independent of total pressure, so they derived true dimerization constants by extrapolation of apparent values to zero pressure. The pressure dependence of apparent values of for acetic acid has also been remarked upon by Miksch et al. who criticized other workers for attempting to express the real-gas behaviour in the form of a virial equation with no term higher than B [cf. equation (29) and the discussion following]. 

Some selected basic properties of water are given in Table 15.1. The unique characteristics of water, although not obvious, will become apparent as we learn more about it. The three-dimensional phase diagram for water, up to the pressure of 10,000 atm and for the temperature range of —50°C to - - 50°C, is shown in Fig. 15.1. The density of ice (ice I) is less than that of water up to about 2,200 atm. Above this pressure, ice exists in various different crystalline modifications. The two-dimensional phase diagram for water is shown in Fig. 15.2, where the triple point, 0.0100°C, consists of solid ice, water, and water vapor at 4.579 torr in equilibrium. Also shown is the critical point above which liquid water cannot exist in the liquid state. The negative slope of the P-T line is due to the difference in molar volumes of liquid and solid, that is, (V, — VJ < 0, and because... 

In fact it is the density p (or molar volume V), rather than pressure, which is the theoretically important independent variable. This is apparent from consideration of Figures 5.1 and 5.2 for the viscosity of argon (Haynes 1973) at four different temperatures, of which one is below the critical temperature. Whereas at low pressure the viscosity increases with increase in temperature as a result of purely kinetic effects, at high pressures the temperature derivative (dr]/dT)p has the opposite sign as collisional... 

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