Liquid phase boundary definition

A triple point is a point where three phase boundaries meet on a phase diagram. For water, the triple point for the solid, liquid, and vapor phases lies at 4.6 Torr and 0.01°C (see Fig. 8.6). At this triple point, all three phases (ice, liquid, and vapor) coexist in mutual dynamic equilibrium solid is in equilibrium with liquid, liquid with vapor, and vapor with solid. The location of a triple point of a substance is a fixed property of that substance and cannot be changed by changing the conditions. The triple point of water is used to define the size of the kelvin by definition, there are exactly 273.16 kelvins between absolute zero and the triple point of water. Because the normal freezing point of water is found to lie 0.01 K below the triple point, 0°C corresponds to 273.15 K. 

The purpose of this chapter is to introduce the effect of surfaces and interfaces on the thermodynamics of materials. While interface is a general term used for solid-solid, solid-liquid, liquid-liquid, solid-gas and liquid-gas boundaries, surface is the term normally used for the two latter types of phase boundary. The thermodynamic theory of interfaces between isotropic phases were first formulated by Gibbs [1], The treatment of such systems is based on the definition of an isotropic surface tension, cr, which is an excess surface stress per unit surface area. The Gibbs surface model for fluid surfaces is presented in Section 6.1 along with the derivation of the equilibrium conditions for curved interfaces, the Laplace equation. 

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). 

Since the fiber is heavier than the liquid, it would sink when placed on the liquid if it were not sustained by an upward force caused by the surface tension of the liquid. This force is exerted at the three-phase air-liquid-fiber boundary lines. If the contact angle 0 and the surface tension y are high enough, this upward force can become sufficient to balance the sinking force, and the fiber will come to rest when the two forces become equal, at an equilibrium depth corresponding to a definite value of < . In this situation, as shown in Figure 1, the force exerted vertically upward on a unit length (1 cm.) of fiber, measured in dynes, will be ... 

In making all operating and design decisions. It Is Important to keep in mind the definition of the true reaction zone. Fundamentally, this Is the Interfaclal area between the immiscible hydrocarbon and acid catalyst liquid phases in the reactor. Reactants and products flow across this boundary. The olefins In the feed stream react Instantaneously with the sulfuric acid catalyst and combine with the relatively small amount of isobutane present In solution In the acid catalyst to form alkylate. Alkylate passes out through the Interfaclal surface reaction boundary into the hydrocarbon phase while Isobutane passes in to resaturate the catalyst. To suppress undesirable polymerization and other reactions It Is necessary to ... 

What we mean in this report by equilibrium and disequilibrium requires a brief discussion of definitions. Natural physicochemical systems contain gases, liquids and solids with interfaces forming the boundary between phases and with some solubility of the components from one phase in another depending on the chemical potential of each component. When equilibrium is reached by a heterogeneous system, the rate of transfer of any component between phases is equal in both directions across every interface. This definition demands that all solution reactions in the liquid phase be simultaneously in equilibrium with both gas and solid phases which make contact with that liquid. Homogeneous solution phase reactions, however, are commonly much faster than gas phase or solid phase reactions and faster than gas-liquid, gas-solid and... 

For heavier olefins it becomes necessary to consider an organic phase so that the system contains gaseous reactants (CO and H2) in contact with the organic phase where they dissolve. The boundary region is certainly formed by the alkene and dissolved CO/H2 in close vicinity with the catalyst in the aqueous phase. Such a situation is most often called a transfer phenomenon between the two liquid phases, but clearer definitions should clarify this general problem [8]. 

It is well known that colloidal suspensions can share many features with simple molecular systems such as gas, liquid, and solid crystalline and amorphous glass phases. This is particularly true when the colloid is nearly monodisperse for then the interparticle interactions, which are usually size dependent, are nearly all the same and hence the phase boundaries, which depend on the interactions, are distinct. Indeed, as the size distribution of a colloid narrows, one could claim that the colloidal suspension transforms into a solution, just as the different particles, by becoming alike or even identical, are transforming to molecules. Unlike simple molecular systems, which by their definition have no variety and are not dissolved in a medium, particle colloids and solutions can vary the interactions via changing size, surface groups, solvent, etc., and thereby change the phase diagram. 

In general, a phase is defined as any homogeneous part of a system that is physically distinct being separated from other parts of the system by a definite boundary, in thermodynamic equilibrium, e.g. water molecules at 1 atm, between 0 and 100 °C are in tbe liquid phase at higher temperatures water is in the vapour phase. 

Almost all the separatory and clean-up methods relevant to this book are ultimately based on differences in partition coefficients of various compounds between two phases. The concept of a phase in the present context (see also Section 4.3.2e) is that of a portion of matter that is separated from others by a clearly defined boundary thus, solid, liquid and gas phases satisfy this definition, but it is possible to have two distinguishable liquid phases (e.g., water and carbon tetrachloride). A simple example of an application of the latter, that is familiar to anyone who has taken an organic chemistry laboratory course, is liquid-liquid extraction a first step in purification of a desired synthesized compound is often to place the crude... 

Point T in Figure 1.12 marks the meeting point of the three different phase boundaries and is known as the triple point. The triple point occurs at a unique temperature, volume, and pressure for a material, and at this point all three phases (solid, liquid, and gas) may coexist. The triple point of water is particularly important as it provides the definition of the kelvin (K), the SI unit of thermodynamic temperature. In 1954, the General Conference on Weights and Measures Conference Generate des Poids et Mesures, GCPM), an international organization responsible for the SI system of measures, defined the kelvin unit as the fraction 1/273.16 of the thermodynamic temperature of the triple point of water. ... 

The strict definition of a phase is any homogeneous and physically distinct region that is separated from another such region by a distinct boundary . For example a glass of water with some ice in it contains one component (the water) exhibiting three phases liquid, solid, and gaseous (the water vapour). The most relevant phases in the oil industry are liquids (water and oil), gases (or vapours), and to a lesser extent, solids. 

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