Critical condensation point

The lower limit of the region of retrograde condensation CC is often called critical condensation point. At CC the highest concentration of the low boiler in the vapor phase is obtained in equilibrium with the liquid phase. At this point the dew-point curve runs vertically and thus the slope for a given temperature is... 

In Fig. 15 we show similar results, but for = 10. Part (a) displays some examples of the adsorption isotherms at three temperatures. The highest temperature, T = 1.27, is the critical temperature for this system. At any T > 0.7 the layering transition is not observed, always the condensation in the pore is via an instantaneous filling of the entire pore. Part (b) shows the density profiles at T = 1. The transition from gas to hquid occurs at p/, = 0.004 15. Before the capillary condensation point, only a thin film adjacent to a pore wall is formed. The capillary condensation is now competing with wetting. 

If a gas is cooled below its critical temperature the )ressure which has to be applied to produce liquefaction j much reduced. Now, since the boiling point of a iquid and the condensing point of a vapour under the ame pressure are the same temperature, the boiling loints of the various gases contained in blue water gas an be studied with advantage. 

Trouton s rule phys chem An approximation rule for the derivation of molar heats of vaporization of normal liquids at their boiling points. traCit anz. riil ) true condensing point See critical condensation temperature. trii kan dens ir). point) true electrolyte puys chem A substance in the solid state that consists entirely of ions. trir i lek-tr9,lTt)... 

For the aromatic pathway (Figure 30.20), the critical control points are the condensation of phosphoenolpyruvate and erythrose-4-phosphate to 3-deoxy-D-arabinoheptulosonate 7-phosphate, DAHP, by DAHP synthase. For tryptophan, the formation of anthranilic acid from chorismic acid by anthranilate synthase is the second critical control point. The transcriptional regulation was overcome through the use of alternative promoters and allosteric regulation was circumvented by the classical technique of selection for feedback-resistant mutants using toxic analogues of the repressing compounds. 

Typical results are shown in Fig. 6 for U-methane in graphite pores of H =7.5 at T=114 K. At p/ps=l the system is solid-like at this temperature, but a discrete change in density occurs around p ps ca.0.5. The self diffiisivity along axial direction also shows drastic change at this point. Further examination of various characteristics of molecular state such as snapshots, in-plane pair correlations and static structure factors confirmed that this change in density is the result of a phase transition from solid-like state to liquid-like one, or melting. Since the critical condensation condition for this pore is far lower than this transition point to stay around p ps= ca.0.2, the liquid-like state is not on metastable branch but thermodynamically stable. Thus a solid-liquid coexistence point is found for this temperature. 

At the point C the two liquid layers become identical, and this is called the critical solution point or con-solute point. If the total applied pressure is varied, both the critical temperature and composition of the critical mixture alter and we obtain a critical solution line. As an example of this we give in table 16. If the dependence of the critical solution temperature on pressure for the system cyclohexane -f aniline. An increase of pressure raises the critical solution temperature, and the mutual solubility of the two substances is decreased. We saw earlier that the applied pressure had only a small effect on the thermodynamic properties of condensed phases, and we notice in this case that an increase of pressure of 250 atm. alters the critical temperature by only 1.6 °C. 

Figure 3.20 shows the computed results and data for a near-critical condensate. The figure shows that as the if-values approach one (i.e., critical point), the prediction results deviate from the measured data. 

Kanda H., Miyahara M. and Higashitani K., Triple point of Lennard-Jones fluid in slit pore - solidification of critical condensate -, J. Chem. Phys. 120 (2004) pp. 6173-6179. 

The initial temperature of a gas condensate lies between the critical temperature and the cricondotherm. The fluid therefore exists at initial conditions in the reservoir as a gas, but on pressure depletion the dew point line is reached, at which point liquids condense in the reservoir. As can be seen from Figure 5.22, the volume percentage of liquids is low, typically insufficient for the saturation of the liquid in the pore space to reach the critical saturation beyond which the liquid phase becomes mobile. These... 

As a general rule, adsorbates above their critical temperatures do not give multilayer type isotherms. In such a situation, a porous absorbent behaves like any other, unless the pores are of molecular size, and at this point the distinction between adsorption and absorption dims. Below the critical temperature, multilayer formation is possible and capillary condensation can occur. These two aspects of the behavior of porous solids are discussed briefly in this section. Some lUPAC (International Union of Pure and Applied Chemistry) recommendations for the characterization of porous solids are given in Ref. 178. 

Values recalculated into SI units from those of Din. Theimodynamic Functions of Gases, vol. 2, Butterworth, London, 1956. Above the solid line the condensed phase is solid below the line it is liquid, t = triple point c = critical point. 

Condensed and converted from tables of Prydz, NBS Rep. 9276, 1967. c = critical point. 

Rounded and condensed from Coucb, E. J. and K. A. Kobe, Univ. Texas Rep., Cent. DAI-23-072-ORD-685, June 1, 1956. c = critical point. 

Environmental conditions under which solvent release from the adhesive on the substrate is produced must be carefully controlled. Humidity is critical because loss of heat due to solvent evaporation may allow attainment of the dew point (the evaporation of the solvent is an endothermic process), and then condensation of water on the adhesive can result. This phenomenon is often called moisture blooming. The presence of water on the adhesive film causes a detrimental effect because the autoadhesion of rubber chains is greatly inhibited. Therefore, humidity must be controlled and avoided by increasing the temperature during solvent evaporation. 

M. Thommes, G. H. Findenegg. Pore condensation and critical-point shift of a fluid in controlled-pore glass. Langmuir 70 4270-4277, 1994. 

A. de Keizer, T. Michalski, G. H. Findenegg. Fluids in pores experimental and computer simulation studies of multilayer adsorption, pore condensation and critical point shifts. Pure Appl Chem (55 1495-1502, 1991. 

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