Solids solid-vapor phase transition

Vapor Pressure Equations of Adamantane and Diamantane for Eiquid-Vapor and Solid-Vapor Phase Transitions... 

In pharmaceutical systems, both heat and mass transfer are involved whenever a phase change occurs. Lyophilization (freeze-drying) depends on the solid-vapor phase transition of water induced by the addition of thermal energy to a frozen sample in a controlled manner. Lyophilization is described in detail in Chapter 16. Similarly, the adsorption of water vapor by pharmaceutical solids liberates the heat of condensation, as discussed in Chapter 17. 

Solid-Vapor Phase Transition Phase Diagrams... 

With the critical exponent being positive, it follows that large shifts of the critical temperature are expected when the fluid is confined in a narrow space. Evans et al. computed the shift of the critical temperature for a liquid/vapor phase transition in a parallel-plates geometry [67]. They considered a maximum width of the slit of 20 times the range of the interaction potential between the fluid and the solid wall. For this case, a shift in critical temperature of 5% compared with the free-space phase transition was found. From theoretical considerations of critical phenomena... 

The heat of vaporization is 13.98 kcal./mol.3 The solid undergoes a phase transition between 100 and 125°. The high-temperature form is cubic and belongs to the space group Tl-PaS with eight molecules per unit cell the lattice parameter a0 is 12.21 A. at 125°31 and 12.00 A. at room temperature.32 The low-temperature form is of lower symmetry.31... 

Ethanol has the higher vapor pressure at 25°C. First, notice that a freezing point and a melting point are the same thing — that point is the temperature at which a substance undergoes the liquid-to-solid or solid-to-liquid phase transition. Next, compare the freezing/melting points of... 

Recently a series of 15 metal carbonyls has been studied by UPS (and XPS) in both the solid and vapor phases (287). The observations on these carbonyls were compared to the photoelectron spectra of CO adsorbed on transition metal surfaces. 

We saw in Section 10.5 that the vapor pressure of a liquid rises with increasing temperature and that the liquid boils when its vapor pressure equals atmospheric pressure. Because a solution of a nonvolatile solute has a lower vapor pressure than a pure solvent has at a given temperature, the solution must be heated to a higher temperature to cause it to boil. Furthermore, the lower vapor pressure of the solution means that the liquid /vapor phase transition line on a phase diagram is always lower for the solution than for the pure solvent. As a result, the triplepoint temperature Tt is lower for the solution, the solid/liquid phase transition line is shifted to a lower temperature for the solution, and the solution must be cooled to a lower temperature to freeze. Figure 11.12 shows the situation. 

Vadas, E.B., Toma, P, and Zogra, G. (1991). Solid-state phase transitions initiated by water vapor sorption of crystalline L-660,711, a leukotriene PeceptorantagonislJharm. Res., 8 148-155. 

F2N.C( NF).NF.CFg.NF2 mw 232.04, N 24.14%, FB 0.0% (See preceding entry) colorless Uq, bp 55°, mp below —130°, vap pres 124mm at 10° Prepd by fluorinating cy a noguanidine with nitrogen diluted fluorine and a sodium-magnesium fluoride mixt at 0° Proposed as an oxidizer for proplnts. Extremely expl and especially sensitive when undergoing solid-liquid phase transition. Best handled with a CF Cl slush bath at —130 to —145°. Do not let vapors contact mercuty... 

Figure 8.7 The increase in the entropy of a substance at constant pressure from absolute zero to its gaseous state at some temperature. The vertical jumps at the melting and boiling points represent the contributions to S due to the solid-liquid and hquid-vapor phase transitions.

Figure 7.3 depicts the energy F e) of a wetted solid for a wide range of liquid thicknesses, ranging from the microscopic to the macroscopic. We may deduce from the figure that, just as in the case of phase separation (segregation of binary mixtures, liquid-vapor phase transition), there are two mechanisms for the drop to recede. 

Solid-gas phase transition (heat of sublimation of dry ice) absorbent type... Lithium bromide-water, water-ammonium etc. adsorbent type... Zeolite-water vapor, silica gel-water vapor etc. 

Figure 63 Left panel liquid-vapor phase transitions of bulk fluid (horizontal hnes) shown mT - p coordinates together with the bulk coexistence curve (dashed line). Right panel the same transitions shown as isotherms at Ti < 72 < 73 in /j - P coordinates (solid hnes).

F i g u re 64 Liquid-vapor phase transition of bulk fluid (right panel, thin solid line) and in hydrophilic pore (dashed lines) and hydrophobic pore (dotted lines). Condensation in pore with a neutral wall, which happens at the same pressure as the bulk transition, is shown by solid line in left panel. 

The porous materials are known to be of importance in many different industrial processes e.g., catalysis, oil recovery, soil pollution, chromatography and separation. In all these systems, the pore structure is known to determine the physico-chemical characteristics. The pore shape and form is not easily determined. Microsporous material is not easily analyzed using electron microscope or diffraction methods, when the mean pore-radius is 2 -50 fjm. One generally uses mercury porosimetry for larger pores, which is based on a capillary phenomena. Other methods have also been used, which are based upon the effect of the curvature of a liquid on its solid - liquid phase transition equilibria, i.e. freezing point depression, vapor pressure or heat of evaporation. 

Foot et al. [22] have determined experimentally the high-pressure phase behavior of the binary systems (butane adamantane) and (butane -I- diamantane). The phase behavior of these binary systems is shown schematically in Figure 1.7. Because the phase diagrams of pure adamantane and diamantane show a solid-solid (si + S2) transition line the curve representing the (solid diamondoids -I- liquid + vapor) equilibrium will split into two branches. One branch corresponds to the (si -f 1 -f v) equilibrium and the other branch corresponds to the (. 2 1 ) equilibrium. Both branches intersect at the (si S2) equilibrium line of the pure diamondoids. The... 

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