Phases Solids

Solid phosgene exists in three crystalline forms, identified by the following melting temperatures and calorimetrically-determined enthalpies of fusion solid I, T, = 145.37 K  

The thermodynamic functions of solids I and II are recorded in Table 6.5 [752]. Those of solid III have not been determined, but it is considered that the heat capacity of solid III is similar to the values for solids I and II. The earlier values of Cp [751] for solid II are valid below 118.3 K, and are valid for solid I above 118.3 K. 

The entropy of COCIj(s) II at the melting point is greater than that calculated by integrating Cpd(lnT) from 0 K to by about 0.84 J mol K . This discrepancy is attributed to Cl/O exchange disorder in the crystal. 

Units of J mol K Values for solid II (theoretical) if thermodynamic equilihrium were obtained. m solid III. 7 for solid II. for solid I. 

The transition energies between the soiid phases have been estimated [752]. For 

One persistently puzzling experimental fact in solid-state transformations of carbons exposed to HTT is the relative growth of crystallite width La) and crystallite height (Lc). It remains essentially unexplored since Franklin s incisive and influential discussions based on her pioneering x-ray diffraction analyses 

PHYSICOCHEMICAL PROPERTIES OF CARBON MATERIALS A BRIEF OVERVIEW 

For example, if about 2% of the carbon active sites remain after 1 second at 1200 K, the thermal annealing submodel of the CBK model predicts that 0.1% remains at 1900 K. 

A special case of annealing, distinguishable by its very rapid rate and elusive quantification, is nascent site deactivation (NSD). Figme 1.14 illustrates fom possibilities at the molecular level. Upon desorption of CO (e.g., during carbon 

Surface diffusion as a solid-phase process is conceptually similar to those discussed above, except that it involves the movement of heteroatoms rather than carbon atoms. Oxygen and hydrogen are of special interest, because of the widely documented importance of their spillover on the carbon surface. Indeed, the phenomenon of spillover was first observed on the surface of a channel carbon black [238]. 

Let us now consider a molecule A in the solid phase of a given crystalline modification. Irradiation of this crystalline phase leads to excitation of A to its first excited singlet state, which can (a) react to give product, (b) decay to the ground state by radiative or nonradiative processes, (c) undergo intersystem crossing to the triplet, which can (1) react to give product, or (2) decay to 

Topochemical control of solid state dimerizations is well illustrated by the example of the /ra j-cinnamic acids. The a form of tron cinnamic acid is known to have a molecular separation of 3.6 A between double bonds and the molecules are arranged in a head-to-tail fashion. j3 Cinnamic acid has approximately the same intermolecular distance in the crystal but the molecules are arranged in a parallel head-to-head manner. a-Truxillic (101) and /3-truxinic (102) adds are the products expected and observed  

The third crystalline form, /-cinnamic acid, is photochemically stable since the intermolecular distance (4.7-5.1 A) is apparently too large for bond formation to occur. 

Topochemical control is also revealed by closely related compounds showing significant differences in chemical behavior in the solid state. For example, cinnamylidenemalonic acid (103) dimerizes in the solid state to cyclobutane (104), while cinnamylideneacetic acid (105) dimerizes to cyclobutane (106y  

Crystalline methyl-o-cyanocinnamylideneacetate (107) forms dimer (108) upon irradiation, while the ethyl ester (109) yields an open-chain dimer (110)  

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The performance of fluidized-bed reactors is not approximated by either the well-stirred or plug-flow idealized models. The solid phase tends to be well-mixed, but the bubbles lead to the gas phase having a poorer performance than well mixed. Overall, the performance of a fluidized-bed reactor often lies somewhere between the well-stirred and plug-flow models. 

Berlin green, FeFe(CN)mechanism postulated for the interchange of substituents in trigonal-bipyramidal 5-co-ordinate complexes, e g. PF, and its substituted derivatives. berthoUide compound Solid phases showing a range of composition. 

Gel permeation chromatography, exclusion chromatography. gel filtration chromatography. A technique for separating the components of a mixture according to molecular volume differences. A porous solid phase (a polymer, molecular sieve) is used which can physically entrap small molecules in the pores whilst large molecules pass down the column more rapidly. A solvent pressure up to 1000 psi may be used. 

The solid phase can be considered as a pure substance or a solid solution. 

When pure component i constitutes the solid phase, the liquid-solid equiiibrium obeys the following equation ... 

This study detects the defect of the void and the exfoliation in the solid phase diffusion bonding interface of ductile cast iron and stainless steel with a nickel insert metal using ultrrasonic testing method, and examine the influence of mutual interference of the reflectional wave both the defect and the interface. 

This study was in real time measured that the reflective echo height of the bonding interface in the solid phase diffused bonding process of carbon steel and titanium using ultrasonic testing method. As a result, the following were made discernment. 

On the other hand, the reliability of the product improves, too, if each state of the plasticity deformation, the creep deformation, and the diffusion joint in the solid phase diffusion bonding as the bonding process, is accurately understood, and the bonding process is controlled properly. 

The three general states of monolayers are illustrated in the pressure-area isotherm in Fig. IV-16. A low-pressure gas phase, G, condenses to a liquid phase termed the /i uid-expanded (LE or L ) phase by Adam [183] and Harkins [9]. One or more of several more dense, liquid-condensed phase (LC) exist at higher pressures and lower temperatures. A solid phase (S) exists at high pressures and densities. We briefly describe these phases and their characteristic features and transitions several useful articles provide a more detailed description [184-187]. 

The usual situation, true for the first three cases, is that in which the reactant and product solids are mutually insoluble. Langmuir [146] pointed out that such reactions undoubtedly occur at the linear interface between the two solid phases. The rate of reaction will thus be small when either solid phase is practically absent. Moreover, since both forward and reverse rates will depend on the amount of this common solid-solid interface, its extent cancels out at equilibrium, in harmony with the thermodynamic conclusion that for the reactions such as Eqs. VII-24 to VII-27 the equilibrium constant is given simply by the gas pressure and does not involve the amounts of the two solid phases. 

Density functional theory from statistical mechanics is a means to describe the thermodynamics of the solid phase with information about the fluid [17-19]. In density functional theory, one makes an ansatz about the structure of the solid, usually describing the particle positions by Gaussian distributions around their lattice sites. The free... 

Two nucleation processes important to many people (including some surface scientists ) occur in the formation of gallstones in human bile and kidney stones in urine. Cholesterol crystallization in bile causes the formation of gallstones. Cryotransmission microscopy (Chapter VIII) studies of human bile reveal vesicles, micelles, and potential early crystallites indicating that the cholesterol crystallization in bile is not cooperative and the true nucleation time may be much shorter than that found by standard clinical analysis by light microscopy [75]. Kidney stones often form from crystals of calcium oxalates in urine. Inhibitors can prevent nucleation and influence the solid phase and intercrystallite interactions [76, 77]. Citrate, for example, is an important physiological inhibitor to the formation of calcium renal stones. Electrokinetic studies (see Section V-6) have shown the effect of various inhibitors on the surface potential and colloidal stability of micrometer-sized dispersions of calcium oxalate crystals formed in synthetic urine [78, 79]. 

It is observed that in most instances a liquid placed on a solid will not wet it but remains as a drop having a definite angle of contact between the liquid and solid phases. The situation, illustrated in Fig. X-2, is similar to that for a... 

These concluding chapters deal with various aspects of a very important type of situation, namely, that in which some adsorbate species is distributed between a solid phase and a gaseous one. From the phenomenological point of view, one observes, on mechanically separating the solid and gas phases, that there is a certain distribution of the adsorbate between them. This may be expressed, for example, as ria, the moles adsorbed per gram of solid versus the pressure P. The distribution, in general, is temperature dependent, so the complete empirical description would be in terms of an adsorption function ria = f(P, T). 

It is noted in Sections XVII-10 and 11 that phase transformations may occur, especially in the case of simple gases on uniform surfaces. Such transformations show up in q plots, as illustrated in Fig. XVU-22 for Kr adsorbed on a graphitized carbon black. The two plots are obtained from data just below and just above the limit of stability of a solid phase that is in registry with the graphite lattice [131]. 

Fig. XVII-22. Isosteric heats of adsorption for Kr on graphitized carbon black. Solid line calculated from isotherms at 110.14, 114.14, and 117.14 K dashed line calculated from isotherms at 122.02, 125.05, and 129.00 K. Point A reflects the transition from a fluid to an in-registry solid phase points B and C relate to the transition from the in-registry to and out-of-registry solid phase. The normal monolayer point is about 124 mol/g. [Reprinted with permission from T. P. Vo and T. Fort, Jr., J. Phys. Chem., 91, 6638 (1987) (Ref. 131). Copyright 1987, American Chemical Society.]...

Traditionally one categorizes matter by phases such as gases, liquids and solids. Chemistry is usually concerned with matter m the gas and liquid phases, whereas physics is concerned with the solid phase. However, this distinction is not well defined often chemists are concerned with the solid state and reactions between solid-state phases, and physicists often study atoms and molecular systems in the gas phase. The tenn condensed phases usually encompasses both the liquid state and the solid state, but not the gas state. In this section, the emphasis will be placed on the solid state with a brief discussion of liquids. 

We discuss classical non-ideal liquids before treating solids. The strongly interacting fluid systems of interest are hard spheres characterized by their harsh repulsions, atoms and molecules with dispersion interactions responsible for the liquid-vapour transitions of the rare gases, ionic systems including strong and weak electrolytes, simple and not quite so simple polar fluids like water. The solid phase systems discussed are ferroniagnets and alloys. 

The CS pressures are close to the machine calculations in the fluid phase, and are bracketed by the pressures from the virial and compressibility equations using the PY approximation. Computer simulations show a fluid-solid phase transition tiiat is not reproduced by any of these equations of state. The theory has been extended to mixtures of hard spheres with additive diameters by Lebowitz [35], Lebowitz and Rowlinson [35], and Baxter [36]. 

Reiss H and Hammerich ADS 1986 Hard spheres scaled particle theory and exact relations on the existence and structure of the fluid/solid phase transition J. Phys. Chem. 90 6252... 

Eleetron energy-loss speetroseopy is used for obtaining speetroseopie data as a eonvenient substitute for optieal speetroseopy, and, taking advantage of diflferenees in seleetion rules, as an adjimet to optieal speetroseopy. In addition, eleetron speetroseopy has many applieations to ehemieal and stnietural analysis of samples in the gas phase, in the solid phase, and at the solid-gas interfaee. 

Figure B3.3.9. Phase diagram for polydisperse hard spheres, in the volume fraction ((]))-polydispersity (s) plane. Some tie-lines are shown connecting coexistmg fluid and solid phases. Thanks are due to D A Kofke and P G Bolhuis for this figure. For frirther details see [181. 182].

Hoover W G and Ree F H 1967 Use of computer experiments to locate the melting transition and calculate the entropy in the solid phase J. Chem. Phys. 47 4873-8... 

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