Phase diagrams interpretation

The key to the study of phase equilibria is the phase diagram, interpreted by the phase rule and the Clapeyron equation. Such phase diagrams will serve as the basis for our discussion. 

J 12 Interpret a two-component phase diagram and discuss fractional distillation (Sections 8.18, 8.19, and 8.20). 

Alloys of lead and thallium have a structure based upon cubic closest packing from 0 to about 87-5 atomic percent thallium. The variation of the lattice constant with composition gives strong indication that ordered structures PbTl, and PbTl, exist. In the intermediate ranges, solid solutions of the types Pb(Pb,Tl)a and Pb(Pb,Tl)TlB exist. Interpretation of interatomic distances indicates that thallium atoms present in low concentration in lead assume the same valence as lead, about 2-14, and that the valence of thallium increases with increase in the mole fraction of thallium present, having the same value, about 2-50, in PbTls and PbTl, as in pure thallium. A theory of the structure of the alloys is presented which explains the observed phase diagram,... 

The Li-Zn phase diagram shows the presence of eight intermediate phases. Later x-ray diffraction results confirm the existence of five intermediate RT phases " . Polymorphism is shown by the three compounds shown in the Li-Cd phase system, and this has confused the interpretation of x-ray diffraction patterns ". 

Recognijtlng types f solids 0 Depict i ng s irnple crystal ty pes 0 DratATing jnd interpreting phase diagrams... 

Data for the hydrogen sulfide-water and the methane-n-hexane binary systems were considered. The first is a type III system in the binary phase diagram classification scheme of van Konynenburg and Scott. Experimental data from Selleck et al. (1952) were used. Carroll and Mather (1989a b) presented a new interpretation of these data and also new three phase data. In this work, only those VLE data from Selleck et al. (1952) that are consistent with the new data were used. Data for the methane-n-hexane system are available from Poston and McKetta (1966) and Lin et al. (1977). This is a type V system. 

The information available on aqueous polymer blends is qualitative in nature because of the lack of a suitable theory to interpret the experimental observations. Mixed gels can be comprised of an interpenetrating network, a coupled network (as discussed above), or a phase-separated network [2]. The latter is the most common as the blends have a tendency to form two phases during gelation. In such cases the miscibility and thermodynamic stability have to be empirically investigated and proper conditions for miscible blends identified. This involves a phase diagram study as is described in [3]. 

E. G. Ehlers, The Interpretation of Geological Phase Diagrams, Freeman, San Francisco, 1972. 

In fact, phase diagrams as in Figure 2.2 form indispensable background information for the interpretation of reduction experiments. However, one should realize that equilibrium data as in Figure 2.2 and Table 2.1 refer to the reduction of bulk compounds. Figures valid for the reduction of surface phases may be quite different. Also, traces of water present on the surface of catalyst particles or on the support represent a locally high concentration and may cause the surface to be oxidized under conditions which, interpreted macroscopically, would give rise to complete reduction. 

From LEED measurements of H monolayers adsorbed on Fe(110) Imbihl et al. proposed a phase diagram as shown in Fig. IS. In addition to lattice gas and lattice fluid phases, two commensurate ordered phases were identifled, denoted as (2 x 1) and (3 x 1) in the figure (cf. Fig. 16). The shaded regions are interpreted as incommensurate phases or as phases composed of antiphase domains their signature is that the LEED spot does not occur at the Bragg position but rather the peak is splitted and satellites appear (Fig. 17). 

Fig. IS. Phase diagram of the H/Fe(110) system, as detenniiied from LEED intensities. Fuli dots represent experimentally determined data points shaded areas correspond to incommensurate or antiphase domain regions. A possible interpretation for the ordered (2 x 1) and (3 x 1) phases is indicated in Fig. 16, assuming that the adsorption sites form a centered rectangular lattice as shown in Fig. lb. (From Imbihl et...

The interpretation of Equations (14.63) and (14.64) can be illustrated graphically by the reduced-phase diagram for a two-component system at constant pressure, as shown for the system diopside-anorthite in Figure 14.3. 

In Chapter 13 we discussed briefly the solid-liquid equilibrium diagram of a feldspar. Feldspar is an ideal, solid solution of albite (NaAlSiaOg) and anorthite (CaAlSi20g) in the solid state as well as an ideal, liquid solution of the same components in the molten state. The relationships that we have developed in this chapter permit us to interpret the feldspar phase diagram (Figure 13.4) in a quantitative way. 

All these results support our kinetic interpretations of these supersaturated gelling solutions. We assume that the network growth is described by the growth of individual domains, each one ruled by the autocatalytic model (S). This system behaves like an assembly of microdomains. Sach steroid in a supersaturation state is a potential germ of microdo.main. According to distribution curves of induction times for each microdomain, the typical kinetic curves for each part A and B of the phase diagram are obtained. 

To interpret the phase diagram in Fig. 7.1 quantitatively, we must return to Eq. (7.3) and more fully define the chemical potential. For ideal gases, the chemical potential can be rigorously derived from statistical mechanics. A useful definition of the ideal-gas chemical potential for O2 is... 

The phase relationships for a normal substance are represented in the phase diagram shown in Fig. 1.1, which is interpreted in terms of the Phase... 

Supported Cu-Pd catalysts have the potential to provide new alternatives to conventional commercial methanol synthesis catalysts (based on the Cu-ZnO-alumina system). Cu-Pd catalysts are also of industrial interest in hydrogenolysis and CO oxidation (Bulatov 1995). To interpret the catalyst behaviour and selectivity, including CO hydrogenation, a fundamental understanding of the structure, surface structure and stability of the phases in this system is required. The Cu-Pd phase diagram indicates that at temperatures greater than 600 °C, Cu... 

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