Characterization of the solid phase

Characterization of the solid phases Si, A1 and Na contents were determined by proton-induced Y-ray emission (PIGE) (11,57) or by high resolution solid state i—NMR spectroscopy (49,50,58)... 

Cassanello M, Larachi F, Marie MN, Guy C, Chaouki J. Experimental characterization of the solid phase chaotic dynamics in three-phase fluidization. Ind Eng Chem Res 34 2971-2980, 1995. 

Solid-state C NMR techniques have been applied to the characterization of the different phases of several polybibenzoates [25,30], including P7MB, PDTMB and PTEB. The last two polymers offer the advantage of the stability of the mesophase at room temperature. The spectra corresponding to the pure mesophase of these samples only exhibited a broad component, while the spectra of the annealed samples were separated into two components crystal and noncrystal. The shapes of the mesophase and the noncrystal components are very similar, and only modest variations in the relaxation times were observed between these two components. The degree of crystallinity of these samples was determined... 

The supported aqueous phase methodology was applied to the system Pd(OAc)2/5 TPPTS, a catalytic precursor for the Trost-Tsuji reaction. The characterization of the solid by 31P MAS NMR confirms the presence of Pd°(TPPTS)3 as the main surface species. The catalytic properties of the solid were tested for the allylic substitution of E-cinnamylethylcarbonate by different nucleophiles such as ethyl acetoacetate, dimethyl malonate, morpholine, phenol, and 2-mercapto-pyridine. The absence of palladium leaching was demonstrated, and having solved the problem of water leaching from the solid to the organic phase, the SAP-Pd catalyst was successfully recycled several times without loss in its activity. It was used in a continuous flow experiment which... 

As was mentioned in the introduction to this chapter "diffusion-controlled dissolution" may occur because a thin layer either in the liquid film surrounding the mineral or on the surface of the solid phase (that is depleted in certain cations) limits transport as a consequence of this, the dissolution reaction becomes incongruent (i.e., the constituents released are characterized by stoichiometric relations different from those of the mineral. The objective of this section is to illustrate briefly, that even if the dissolution reaction of a mineral is initially incongruent, it is often a surface reaction which will eventually control the overall dissolution rate of this mineral. This has been shown by Chou and Wollast (1984). On the basis of these arguments we may conclude that in natural environments, the steady-state surface-controlled dissolution step is the main process controlling the weathering of most oxides and silicates. 

The phenomena of surface precipitation and isomorphic substitutions described above and in Chapters 3.5, 6.5 and 6.6 are hampered because equilibrium is seldom established. The initial surface reaction, e.g., the surface complex formation on the surface of an oxide or carbonate fulfills many criteria of a reversible equilibrium. If we form on the outer layer of the solid phase a coprecipitate (isomorphic substitutions) we may still ideally have a metastable equilibrium. The extent of incipient adsorption, e.g., of HPOjj on FeOOH(s) or of Cd2+ on caicite is certainly dependent on the surface charge of the sorbing solid, and thus on pH of the solution etc. even the kinetics of the reaction will be influenced by the surface charge but the final solid solution, if it were in equilibrium, would not depend on the surface charge and the solution variables which influence the adsorption process i.e., the extent of isomorphic substitution for the ideal solid solution is given by the equilibrium that describes the formation of the solid solution (and not by the rates by which these compositions are formed). Many surface phenomena that are encountered in laboratory studies and in field observations are characterized by partial, or metastable equilibrium or by non-equilibrium relations. Reversibility of the apparent equilibrium or congruence in dissolution or precipitation can often not be assumed. 

Another traditional method used for polymer support characterization is elemental analysis. Its use as an accurate quantitative technique for monitoring solid-phase reactions has also been demonstrated [146]. Microanalysis can be extremely valuable if a solid-phase reaction results in the loss or introduction of a heteroatom (usually N, S, P or halogen). In addition, this method can be used for determination of the loading level of a functional group (e. g. usually calculated directly from the observed microanalytical data). For example, in many cases, the displacement of chloride from Merrifield resin has been used as a guide to determine the yield of the solid-phase reaction. 

The H-cutve isotherm is characterized by a linear uiCTease that remains independent of the solute concentration in the solution (i.e., constant partitioning of the solute between the solvent and the adsorbing surface). This behavior indicates a high affinity of the solid phase for the solvent. 

Macchi P, Garlaschelli L, Martinengo S, Sironi A (1998) Characterization of the solid-solid phase transition of Co2(CO)g(AsPh3)2. Inorg Chem 37 6263-6268... 

Her research interests are in the characterization of the solid state, and she has over 40 publications in single-crystal Raman studies, X-ray crystallography, zintl phases, pigments, and heterogeneous catalysis. 

Chemical characterization of solids generally involves the characterization of the major phase, which includes the determination of stoichiometry, homogeneity and... 

Y. Bal, K. E. Bal, G. Cote, and A. Lallam. Characterization of the solid third phases that precipitate from the organic solutions of aliquat (r) 336 after extraction of molybdenum)VI) and vanadium(V). Hydrometallurgy, 75(1-4) 123-134, 2004. 

Computational studies have advanced the study of the solid phase of water and of the interfacial region where the phase transition occurs [1-5]. As water exhibits very unusual properties in the liquid phase, it also exhibits peculiar properties in the solid phase as well. Much about the structure of ice is known from x-ray diffraction experiments or computational studies. Some experiments have been performed on the interfacial region between the liquid and solid phase of water to understand the freezing process, but additional studies are still needed to characterize the... 

To make the connection between the observed electrical, optical, etc., behavior and the type and concentration of point defects in a solid compound, one must first have some qualitative ideas as to the expected properties of a solid arising from the presence of a particular type of defect. A simple example is discussed. Further details are given by Kroger and Vink (20, 22). Secondly, some theory must be available which relates the concentration of the various defects to the independent intensive variables of the solid phase and the parameters which characterize the particular compound under study. This theory and some of its applications are discussed below. 

In solid particulate systems, direct observation is justifiably the last word. In emulsions where creaming, sedimentation, and coalescence can change the nature of the sample, microscopic observation has unique sample handling problems. If these special sampling problems are addressed, then microscopy can indeed provide the benchmark for the physical characterization of the dispersed phase in emulsion systems. 

Local isotherms are defined here as sorption relationships resulting from particular classes or types of sorption reactions. For soil and sediment systems involving heterogeneous mixtures of sorbent surfaces and phases, such local isotherms may be expressed at some level of physical division, such as the grain scale. Alternatively, they may be expressed per unit of some quantifiable component of the solid phase that can be characterized by either mineralogical or elemental analysis, such as organic carbon. 

Other important characteristics of porous media include the specific surface area and the tortuosity factor. The specific surface area is defined as the surface area of the solid phase divided by the sample volume (and hence has units of L ), and is important to solid-fiuid interactions (for example, this is an important parameter for activated carbon characterization). The tortuousity factor t in porous media is defined as ... 

Prior to nomination into full development, a candidate drug should undergo a phase traditionally called preformulation. Preformulation is the physicochemical characterization of the solid and solution properties of compounds and although now relatively old, the definition of preformulation proposed by Akers (1976) is particularly apt ... 

The experimentally obtained E-pd dependences for moderately soluble oxides are characterized by a considerable decrease in the e.m.f. in the unsaturated solution section. The formation of the saturated solution is accompanied by a reduction in the slope of the tangent, since under these conditions the weights of the titrant are consumed, mainly, for precipitation of the solid phase. Naturally, this process does not increase the oxide ion concentration in the melt. After complete precipitation of the oxide the slope of the tangent to the E-pd dependence increases, and the dependence itself asymptotically approaches the E-pO calibration line, as can be seen from Fig. 3.6.5. This is because, at high initial concentrations of the titrant, the... 

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