Triple-point density

Colorless, odorless gas density 6.41 g/L about five times heavier than air liquefies at -50.7°C (triple point) density of liquid 1.88 g/mL at -50.7°C sublimes at -63.8°C critical temperature 45.54°C critical pressure 37.13 atm critical volume 199 cm /mol slightly soluble in water soluble in ethanol. 

Recently, the effective mass of the electron has been calculated [148] within a Wigner-Seitz framework [175] for Ar, Kr, and Xe. In all three liquids, m decreases with increasing density. At the triple point densities, m = in argon and m =... 

The variation of the defined dissociation constant, obtained on the basis of this dielectric model, is plotted in Fig. 1.6. The reaction Eq. (1.3) in liquid water becomes unfavorable from the perspective of the free energy upon exceeding 500 K on the saturation curve, where the liquid density falls below about 85% of the triple-point density. Nevertheless, this sulfonic acid head group would still be considered a strong acid in bulk aqueous solution at these elevated temperature and reduced-density conditions. These results give perspective for the view that insufficient hydration can result in incomplete dissociation of sulfonic acid species in membranes. 

Although the mechanism of the melting transition is still not clear, but the phase diagram is now fairly well known. In particular, the triple point temperature is located at 7) = 0.40 0.01 and the triple point density is equal to about p = pa 0.79 [167]. A little more controversial is the location of the critical point. Barker et al. [165] have obtained T 0.56, while more recent Monte Carlo simulation [169] has given a somewhat lower value of 0.50T0.02. The differences in the values of the critical point temperature obtained by different authors are not surprizing, however. The recent Monte Carlo simulations in the Gibbs ensemble [170,171] have clearly demonstrated that the way one cuts the interaction potential considerably influences the estimated critical temperature. It appears that the tail of the interaction potential (beyond the assumed cut-off distance) has a big influence on the obtained results. 

Here, o and s are the familiar Lennard-Jones parameters, p is the number density (p = N/V),N is the number of molecules, and V is the total volume. As a point of reference, the reduced triple-point density and the critical-point density for the liquid in this model occur at PTP[Pg.46]

CP, (374C, 221 bar), and triple point, TP, are indicated on the gas-liquid coexistence curve. The points on the broken line extending from TP to the right denote the transitions between different high pressure modifications of ice. At pressures above 25 kbar, water densities have been derived from shock wave measurements ( 7) At 500 C and 1000 C, pressures of about 8 and 20 kbar are needed to produce the triple point density of liquid water. 

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