P-T diagram

The Class I binary diagram is the simplest case (see Fig. 6a). The P—T diagram consists of a vapor—pressure curve (soHd line) for each pure component, ending at the pure component critical point. The loci of critical points for the binary mixtures (shown by the dashed curve) are continuous from the critical point of component one, C , to the critical point of component two,Cp . Additional binary mixtures that exhibit Class I behavior are CO2—/ -hexane and CO2—benzene. More compHcated behavior exists for other classes, including the appearance of upper critical solution temperature (UCST) lines, two-phase (Hquid—Hquid) immiscihility lines, and even three-phase (Hquid—Hquid—gas) immiscihility lines. More complete discussions are available (1,4,22). Additional simple binary system examples for Class III include CO2—hexadecane and CO2—H2O Class IV, CO2—nitrobenzene Class V, ethane—/ -propanol and Class VI, H2O—/ -butanol. 

Figure 12-16D. Typical compressor ailments and how they look on P-T diagrams. (Used by permission Palmer, E. Y. Petroleum Processing, p. 884, June 1954). National Petroleum News, Adams Business Media.)...

Figure 2-79. Typical P-T diagram for a pure substance (A is the triple point and C is the critical point).

Figure 1.37. Estimation of minimum depth of seawater at the time of Kuroko mineralization. P-T diagram of NaCl-H20-C02 is from Drummond (1981) (Ohmoto et al., 1983).

On the P — T diagram, at right, each of the mixed-phase regions is represented by a single co-existence line. The value of the chemical potential must be the same for the two phases at any point on a co-existence line. The lines meet at the triple point where all three phases are in equilibrium. The triple-point line on the P — V diagram is marked TP. 

The temperature domination explains the peninsula in the P-T diagram (Fig. 3.9), and the negative coefficient of reaction rate is due to the shift from point 2 to 3. 

Figure 10.14 is a P-T diagram that illustrates the difference between conventional solvent extraction, supercritical extraction, and distillation. The choice of pressure and temperature area depends on the separation that is required. 

AI is stable at lower temperature while A2 at higher temperature and the transition from A j to A 2 is accompanied by increase in molar volume. Both A j andA2 are denser than the liquid phase. If no metastable equilibria are observed, a P-T phase diagram for the system drawn. Each area of the P-T diagram labelled ... 

A pure substance A exists in three modifications Ai A2 and Ag. At the triple point S j > a2 > o3 and Val>Va2>Vo3,S and V are entropy and volume respectively are there. A suitable P-T diagram on the basis of informations given above and also label the region, line and points constructed ... 

Figure 9.8-7. P-T diagram for solid-liquid transition of monoglyceride in presence of C02.

The order of a transition can be illustrated for a fixed-stoichiometry system with the familiar P-T diagram for solid, liquid, and vapor phases in Fig. 17.2. The curves in Fig. 17.2 are sets of P and T at which the molar volume, V, has two distinct equilibrium values—the discontinuous change in molar volume as the system s equilibrium environment crosses a curve indicates that the phase transition is first order. Critical points where the change in the order parameter goes to zero (e.g., at the end of the vapor-liquid coexistence curve) are second-order transitions. 

T = 7 . above which the liquid and gas phase are no longer distinguishable. Since the liquid can he continuously converted into Ihe gas phase without discontinuous change of properties by any path in the P — T diagram passing above the critical point, there is no definite boundary between liquid and gas. Two liquids ol similar molecules are usually. soluble in all proportions, but very low solubility is sufficiently common to permit the demonstration of as many as seven separate liquid phases in equilibrium at one temperature and pressure (mercury, gallium, phosphorus. perHuoro-kerosene, water, aniline, and heptane at 50 C. I atmosphere). 

Fig. 19. p-T diagram for carbon dioxide after Kennedy.14 Parameters, g. COj / cc. 

The number of degrees of freedom / equals the number of variables which has to be adjusted in order to define the system completely. This rule states that the factors mentioned here cannot be altered randomly without changes occuring in the system. Figure 6.5, the P, T diagram of water, serves to illustrate this. The change in pressure for H20 is represented as a function of temperature. 

Fig-6.6 P,T - diagram of silicon dioxide with some of the possible modifications. 

T, is the temperature of allotropic transformation from a to 3 phase and Tm is the melting point. By combining with the effect of pressure we can construct a P-T diagram for a substance of interest. At a given pressure, say, the atmospheric pressure, Pa, as shown in the following diagram, as the a phase solid is heated, it transforms to the (3 phase at T and the (3 phase, upon further heating, melts at Tm, and the liquid boils at Tv. 

The path is one of constant temperature, so that if wc multiply by T this relation gives the amount of heat absorbed per unit increase of volume. But on account of the nature of the surface, (0P/dT)v is the same for any point corresponding to the same temperature, no matter what the volume is it is simply the slope of the equilibrium curve on the P-T diagram, wdiich is often denoted simply by dP/dT (since in the P-T diagram there is only one independent variable, and we do not need partial derivatives). Then wc can integrate and have the latent heat L... 

This method was later improved by van Lierop and co-workers (6). In this improved version of the method, vaporization of the solvent is completely suppressed by pressurizing the autoclave with an inert gas prior to heating while the subsequent heating is carried out batch at constant volume. Thus, the entire procedure is carried above the vapor-liquid interface of a Pressure-Temperature (P-T) diagram, shown as route A -B (2) in Figure 1. 

The values of measured phase equilibrium data were plotted in P-T diagrams (fig.2) as lines of constant composition (shown for PEG 1500). On the abszisse a... 

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