Pressure-composition diagram

The boiling point increases regularly. The boiling point - composition diagram for such a system is shown in Fig. 1, 4, 2 (the complementary vapour pressure - composition diagram is depicted in Fig. I, 4, 3 for purposes of comparison only). Let us consider the behaviour of such a liquid pair upon distillation. If a solution of composition is heated, the vapour pressure will rise until at the point ij it is equal to the pressure of the atmosphere, and boiling commences at temperature The com-... 

To appreciate the action of a drying agent of class (a), let us imagine some anhydrous copper sulphate in an evacuated vessel provided with a pressure gauge, and water is allowed to enter slowly the temperature is assumed constant at 25°. The results may be best expressed by means of a vapour pressure - composition diagram (Fig. 7, 20, 1). The initial system is represented by the point A the pressure will rise along AB until the monohydrate CuS04,H20 commences to form at B. 

Fig. 2-21. Typical pressure-composition diagram of a two-component mixture with one tie line, 123.

Figure 2—21 gives a typical pressure-composition diagram for a two-component mixture at a single temperature. Combinations of composition and pressure which plot above the envelope indicate conditions at which the mixture is completely liquid. Combinations of composition and pressure which plot below the envelope indicate conditions at which the mixture is gas. Any combinations of pressure and composition which plot within the envelope indicate that the mixture exists in two phases, gas and liquid. Bubble point and dew point have the same definitions as previously discussed. 

Fig, 2-22. isothermal pressure-composition diagrams of mixtures of methane and ethane. (Bloomer, et al., Institute of Gas Technology, Research Bulletin 22, 1953. Reproduced courtesy of Institute of Gas Technology, Chicago.)... 

Figure 2-22 gives pressure-composition diagrams for mixtures of methane and ethane.3 There are four saturation envelopes corresponding to four different temperatures. 

Tie-lines giving the compositions of the liquid and gas in equilibrium are again horizontal. The bubble-point line gives the composition of the equilibrium liquid, and the dew-point line gives the composition of the equilibrium gas. The lengths of the tie-lines represent the quantities of gas and liquid at equilibrium in the same manner as for the pressure-composition diagram. 

Replot two isotherms of the data given in Figure 2-37 as pressure against composition in weight percent. Use temperatures of 75°F and 300°F. This is called a pressure-composition diagram. Label the bubble-point lines and dew-point lines. 2-23. Determine the compositions and quantities of gas and liquid when 10 lb moles of a mixture of 55 mole percent methane, 20 mole percent propane and 25 mole percent n-pentane is brought to equilibrium at 160°F and 1500 psia. 

Figure 34.2 Pressure-composition diagram for binary ideal liquid mixture. Dependence of P on mole fraction (xA,xB) of liquid present. Note. Liquid B is more volatile than liquid A since PB > PA - it exerts a higher (saturated) vapour pressure.

Figure 34.4 Pressure-composition diagram for Ideal Liquid Mixture of toluene and benzene showing liquid and vapour compositions. The region of the plot enclosed and labelled liquid + vapour corresponds to the area of stability of both liquid and vapour.

The microphases group themselves on the pressure composition diagrams into families with related slopes and two-phase regions. 

Figure 7.3 Pressure-composition diagrams of Mg-H, MgjNi-H and Mg2Nio5Cuos Due to alloying the plateau pressure at 7= 300 °C increases while the storage capacity decreases, taken from [35],...

The pressure-composition diagram is related to the composite pressure-temperature diagram previously described in the following manner. In Figure 28 let Ti represent the fixed temperature at which the pressure-composition diagram is to he constructed. This isotherm intersects the two-phase loop of a particular composition at the bubble-point pressure and the dew-point pressure. If these two pressures and the composition are plotted, two points on the pressure-composition... 

In order to more fully understand the meaning of a pressure-composition diagram the behavior of a system which is initially in the vapor phase and which is subjected to an isothermal compression through the two-phase region will be described. In the pressure-... 

Fig. 31. Pressure-composition diagram illustrating an isothermal compression through the two-phase region.

The relationship between the quantities calculated in the example presented above and the phase diagrams previously described should be clearly understood. In Figure 38 the pressure-composition diagram for the propane-butane system is shown. In this diagram tiie composition is expressed in terms of mole fraction of butane. The points... 

A, B, C, and D have been calculated in the preceding example. The point A at 22.75 psia represents the computed bubble-point pressure for a solution whose mole fraction of C4H10 is 0.50. Point B represents the composition of the vapor at the bubble point. Similarly, the points C and D represent the bubble point and composition of the vapor at the bubble point for a solution whose mole fraction of C4Hio>is 0.75. The points E and jP. represent the vapor pressure of pure butane and pure propane, respectively, at 0° F. The line FACE is tile bubble-point line and the line FBDE is the dew-point line. It is obvious that a pressure-composition diagram for any ideal binary system could be calculated in this manner and would serve to describe the phase behavior quantitatively. 

Calmilated pressure-composition diagram for the re-butane-re-pentane system,... 

Prediction of reservoir behavior, 171 ff. Pressure-composition diagram, 65 ff.,... 

Figure 4. Pressure-Composition diagrams for poiy(elhyiene giycoi) carbon dioxide systems at 313 K.

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