Gaseous phase, homogeneous

We are going to consider three types of equilibrium gaseous phase homogeneous, liquid phase homogenous and solid phase homogenous equilibria. 

Thereby, the application of highly sensitive sensors jointly with several specific techniques can be recommended to study complex heterogeneous and homogeneous processes where an experimentalists are faced with an option to analyze small concentrations of active particles in gaseous phase. 

Condensation is generally a transient operation in which, as discussed by Ueda and Takashima(106), simultaneous heat and mass transfer are further complicated by the effects of spontaneous condensation in the bulk gaseous phase. After the creation of supersaturation in the vapour phase, nucleation normally occurs which may be homogeneous in special circumstances, but more usually heterogeneous. This process is followed by both crystal growth and agglomeration which lead to the formation of the final crystal product. As a rate process, the condensation of solids from vapours is less well understood than vaporisation(98). Strickland-Constable(107) has described a simple laboratory technique... 

The most detailed research on nitration in the gaseous phase has been carried out by Wilson and Miles [69]. They concluded that there were no prospects of introducing this method in practice, since the nitrocellulose produced is non-homogeneous, and the nitration is inadmissibly slow. Thus, to reach a nitrogen content of 10% N by vapour phase nitration, at a vapour pressure of 16 mm Hg, a period of 48 hr was needed. 

Window autoclaves have been built to allow one to determine visually the appearance of turbidity in a homogeneous polymer solution, indicating the onset of phase separation, and to observe the resulting number of liquid and gaseous phases and optionally to determine their composition. Lentz [40] developed a mechanically driven stirrer fitted in a 2000-bar window autoclave. This apparatus allowed fast homogenation of concentrated polymer solutions and blends having low viscosity. 

The steady state mass flux (J ) of component i through a homogeneous film of uniform thickness separating two gaseous phases is given by Fick s "First Law of diffusion ... 

Homogeneous reactions are those reactions that occur within a single phase (physical state), especially a liquid or gaseous phase. Heterogeneous reactions are those reactions that take place at least in part at the interface between two phases, such as solid and liquid or liquid and gas, etc. The discussion and problems in this chapter will address homogeneous reactions unless otherwise stated. Please note that rate means that there is a time element involved which is usually expressed in seconds (s), minutes (min), or hours (h). 

The existence of a surface relief poses, naturally, the problem of the geometrical relations between the localization region and the adspecies size. The latter may be somewhat arbitrarily selected in the range between a gas-kinetic diameter and a first incomplete electronic shell, the bond lengths of the surface molecule in some cases differing from those in the gaseous phase. One uses, as a unit of measure, a lattice site area ([Pg.355]

What is the difference between the homogeneous and the heterogeneous formation of nanoparticles in the process of the film deposition from gaseous phase ... 

In our attempts to determine the possible role of free radical lipid peroxidation in smoke induced injury, the levels of lipid peroxidation products - thiobarbituric acid reactants, mainly malondialdehyde - wereQmeasured in lung homogenates with or without prior incubation at 37 C for one hour, contrary to our expectation, the levels of thiobarbituric acid reactants were found to be decreased, rather than increased, in the lungs of cigarette-smoke-exposed rats (Table III). Such a depression effect, however, was observed only when animals were exposed to whole smoke, and not to the gaseous phase of smoke. 

A phase is that portion of a system which is homogeneous. A complicated system can have more than one solid phase corresponding to different crystal structure variations (e.g. pleomorphic forms of CaCXf calcite, aragonite and vaterite). Sometimes it can also have more than one liquid phase but usually contains only one gaseous phase. We can have a system having a total of p phases with c components (i.e. substances) present. Thus many of the important phase systems are more complicated than the simple one-component systems so far discussed. 

CVD is a synthesis process in which the chemical constituents react in the vapor phase near or on a heated substrate to form a solid deposit (Pierson 1999). The reactions happened in the CVD system can be divided into homogeneous gas phase reactions and heterogeneous substrate surface reactions. Normally, CVD technique is utilized to make thin films. CVD is also defined as a process whereby a thin solid film is synthesized from the gaseous phase by a chemical reaction (Hitchman and Jensen 1993). The CVD apparatus arrangement is dependant on the particular application. The apparatus is made up with three major components precursors and... 

Homogeneous catalysts are structurally well-defined complexes and because they are soluble in the reaction mix are not subject to pore diffusion limitations as are heterogeneous catalytic materials. They are almost always highly selective towards desired products. The main consideration is that the complex be stable and reactor conditions chosen such that all the gaseous reactants are adequately dissolved and mixed in the liquid phase. Homogeneous catalysts are easily characterized by standard instrumental methods for compound identification such as XRD or spectroscopy. Deactivation is associated with attack by traces of carboxylic acidic byproducts and impurities in the feed such as 02 and chlorides that attack the ligand groups. 

In a hydrogenation reaction with a soluble catalyst there are liquid and gaseous phases present. Why is the reaction called homogeneous rather than heterogeneous ... 

Photo-initiated AOPs are subdivided into VUV and UV oxidation that are operated in a homogeneous phase, and in photocatalysis (Fig. 5-15). The latter can be conducted in a homogeneous aqueous phase (photo-enhanced Fenton reaction) or in a heterogeneous aqueous or gaseous phase (titanium dioxide and certain other metal oxide catalysts). These techniques apply UV-A lamps or solar UV/VIS radiation and they are in pre-pilot or pilot status. According to Mukhetjee and Ray (1999) the development of a viable and practical reactor system for water treatment with heterogeneous photocatalysis on industrial scales has not yet been successfully achieved. This is mainly related to difficulties with the efficient distribution of electromagnetic radiation (UV/VIS) to the phase of the nominal catalyst. 

The technology of UV disinfection of water and air is based on the direct irradiation of the media, mostly in homogeneous aqueous or gaseous phases. It is weU established in industry, and monochromatic LP or polychromatic MP mercury lamps as sources of UV-C radiation are apphed (cf. Schneider et al., 2001, Kalisvaart, 2001). 

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