Reaction products, separation

The detection of spectral sensitizing action often depends on amplification methods such as photographic or electrophotographic development or, alternatively, on chemical or biochemical detection of reaction products. Separation of the photosensitization reaction from the detection step or the chemical reaction allows selection of the most effective spectral sensitizers. Prime considerations for spectral sensitizing dyes include the range of wavelengths needed for sensitization and the absolute efficiency of the spectrally sensitized process. Because both sensitization wavelength and efficiency are important, optimum sensitizers vary considerably in their stmctures and properties. 

The compound at first precipitated is redissolved at a pH of 11. The solution is treated another time with charcoal and is filtered. Thereafter, a mixture of anhydrous acetic acid and water in a proportion of 1 1 is added with stirring and cooling until a pH of 7 is reached. Thus, the reaction product separates with crystallization. 

Where gr represents the heat input from different sources, Wi the useful work input and denoting the heat to useful work conversion efficiency associated with it. Depending upon the process, work input Wi may be required for different process steps like driving the reaction, reaction-product separation, and mass transfer. AHo is the... 

McWhorter S, Soper SA. Conductivity detection of polymerase chain reaction products separated by micro-reversed-phase liquid chromatography. Journal of Chromatography A 883,1-9, 2000. 

Let us finally comment on the morphological stability of the boundaries during metal oxidation (A + -02 = AO) or compound formation (A+B = AB) as discussed in the previous chapters. Here it is characteristic that the reaction product separates the reactants. 1 vo interfaces are formed and move. The reaction resistance increases with increasing product layer thickness (reaction rate 1/A J). The boundaries of these reaction products are inherently stable since the reactive flux and the boundary velocity point in the same direction. The flux which causes the boundary motion pushes the boundary (see case c) in Fig. 11-5). If instabilities are occasionally found, they are not primarily related to diffusional transport. The very fact that the rate of the diffusion controlled reaction is inversely proportional to the product layer thickness immediately stabilizes the moving planar interface in a one-... 

If one could use heterogeneous catalysts such as dispersed metals to promote this type of reaction, product separation would be facilitated and the more efficient flow processes could be used instead of the commonly employed batch mode. There are, however, a number of problems which must be overcome before such systems can be used practically. In the first place it must be shown that dispersed metals can promote these reactions and, secondly, a more detailed knowledge must be acquired of substrate adsorption on the catalyst and the interaction of the adsorbed species to give the product. 

Ethyl Benzene.—116 gms. of pure benzene are placed in the reaction flask and stirred at about 1,500 revs, per minute, the temperature being maintained at 75°—80°. The reaction is stopped in 3 hours, when on standing the reaction product separates into two layers, the upper almost colourless, the lower brown and viscous. The latter is discarded. 

Equip a 1-litre three-necked flask with a reflux condenser and a sealed mechanical stirrer. Dissolve 50.5 g (0.25 mol) of commercial l-chloro-2,4-dinitrobenzene (1) in 250 ml of rectified spirit in the flask, add the hydrazine solution and reflux the mixture with stirring for an hour. Most of the reaction product separates during the first 10 minutes. Cool, filter with suction and... 

A labeled flowchart of a chemical process involving reaction, product separation, and recycle is shown in Figure 4.5-1. Note the distinction between the fresh feed to the process and the feed to the reactor, which is the sum of the fresh feed and recycle stream. If some of the stream variables shown in Figure 4.5-1 were unknown, you could determine them by writing balances on the overall process and about the reactor, separator, and mixing point. 

With the development of zeolite membranes, the field of possible applications has become much broader. Successful reaction-product separation by zeolite membranes is governed by differences in the affinity of the components with the zeolite framework or by differences in the mobility of the components in the zeolite framework i.e., besides molecular sieving and differences in diffusivities, differences in adsorption appear to be a key factor in separation selectivity [61,174]. 

This guidance has many practical ramifications. If a manufacturer chooses to identify a complex reaction product as a mixture and list each component of the reaction product separately, impurities and byproducts do not have to be separately identified. However, if it subsequently learns that a component... 

In a number of chemical reactions, reaction products separate themselves from the reaction phase and form a separate phase. Gaseous products may evolve, liquid products may seperate or solids may precipitate. These phenomena may influence transport phenomena and consequently complicate the reactor design. If die reaction product is a solid precipitate, it may be necessary to aim the reactor design at obtaining a product with desired particle properties. 

When a reversible chemical reaction takes place in one phase, and one of the reaction products forms another phase, the reaction may approach completion, depending on the nature of the physical equilibrium. Of course, this has been recogniz from the earliest days that chemistry is practised. It may be desirable to select such reaction conditions that the reaction product separates itself from the reaction mixture. When it is the main product that forms a new phase, the formation is in fact also an important puriHcation step. This is the reason that reactions where the main product precipitates are often preferred to homogeneous reactions. 

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