Extraneous components

The introduction of an extraneous component as a heat carrier aflfects the recycle structure of the flowsheet. Figure 4.6a presents an example of the recycle structure for just such a process. 

Whether an extraneous component, product, or feed is used as a heat carrier, the actual configuration, as before, depends on the order of the volatilities (again assuming distillation as the means of separation). 

Absorption. If possible, a component which already exists in the flowsheet should be used as a solvent. Introducing an extraneous component into the flowsheet introduces additional complexity and the possibility of increased environmental and safety problems later in the design. 

Preferably, high pressure Hquid chromatography (hplc) is used to separate the active pre- and cis-isomers of vitamin D from other isomers and allows their analysis by comparison with the chromatograph of a sample of pure reference i j -vitainin D, which is equiUbrated to a mixture of pre- and cis-isomers (82,84,85). This method is more sensitive and provides information on isomer distribution as well as the active pre- and cis-isomer content of a vitamin D sample. It is appHcable to most forms of vitamin D, including the more dilute formulations, ie, multivitamin preparations containing at least 1 lU/g (AOAC Methods 979.24 980.26 981.17 982.29 985.27) (82). The practical problem of isolation of the vitamin material from interfering and extraneous components is the limiting factor in the assay of low level formulations. 

Pressure shift should always be explored as the first option when separating an azeotropic system. Adding extraneous components to a separation should always be avoided if possible. Unfortunately, most azeotropes are insensitive to change in pressure, and at least a 5% change in composition with pressure is required for a feasible separation using pressure shift1. 

Reactor heat carrier. As pointed out in Chapter 7, if adiabatic operation is not possible and it is not possible to control temperature by indirect heat transfer, then an inert material can be introduced to the reactor to increase its heat capacity flowrate (i.e. product of mass flowrate and specific heat capacity). This will reduce temperature rise for exothermic reactions or reduce temperature decrease for endothermic reactions. The introduction of an extraneous component as a heat carrier effects the recycle structure of the flowsheet. Figure 13.6a shows an example of the recycle structure for just such a process. 

Whether an extraneous component, product, feed, byproduct or feed impurity is used as heat carrier, as before, the actual configuration of the separation configuration will change between different processes as the properties on which the separation is based change the order of separation. 

Representative multiple ion mass chromatograms of soil samples are presented in Fig. 5.4. These gas chromatography-mass spectrometric determinations of polychlorodibenzo-p-dioxin and polychlorodibenzofurans, and non-ortho polychlorobiphenyls in differing types of samples serve to exemplify the versatility of the procedure for such analyses. The gas chromatography-mass spectrometric data were usually uncluttered by extraneous components, and interpretation of the data was routinely straightforward. 

Besides the cell wall tissue, which is the basic material of all wood substance, wood contains a variety of materials, many of which may be extracted by selected solvents, These extraneous components lie mainly within the cavities (lumen of the cells and on the surfaces of the cell... 

Wood Extractives. Glue bonds can be affected in many ways by extraneous components on or near the surface of wood. Chen (56) showed that extractive removal did improve bond performance and that the extractives, in part, reduce wettability. This effect is reflected also in Figure 2 from Jordan and Wellons (29). Hergt and Christensen (57) also showed that extractives can slow water adsorption from the adhesive into the wood, thus slowing development of cohesion in the adhesive. 

For each radial wave vector p, the integration over frequency for free energy G (p) can be done by parts. This turns out to be a clean separation into physically real and physically extraneous components ... 

Additional polysaccharides may occur as extraneous components of wood, which are not part of the cell wall for example, the heartwood of species of larch can contain up to 25 percent (dry weight) of arabinogalactan, a water-soluble polysaccharide that occurs only in trace quantities in other wood species.5... 

Sample extraction and cleanup procedures for TLC are similar to those for gas chromatography (GC) and HPLC. If the analyte concentration is sufficiently high, pharmaceutical dosage forms can often be simply dissolved in a solvent that will completely solubilize the analyte and leave excipients or extraneous compounds undissolved to yield a test solution that can be directly spotted for TLC analysis. Grinding of the sample and application of heat and/or sonication may be required to assure solubility of the analyte, as well as filtration or centrifugation to remove undissolved excipients. If the analyte is present in low concentration in a complex sample, solvent extraction, cleanup (purification), and concentration procedures usually precede TLC in order to maximize the analyte and minimize interfering extraneous components in the... 

Extraneous Components. The extraneous components (extractives and ash) in wood are the substances other than cellulose, hemi-celluloses, and lignin. They do not contribute to the cell wall structure, and most are soluble in neutral solvents. The detailed chemistry of wood extractives can be found elsewhere (26). A review of extractives in eastern U.S. hardwoods is available (27). 

Wood Solubility in 1% NaOH. Wood extraction procedures in 1% NaOH (Tappi Standard T 212) extract most extraneous components, some lignin, and low molecular weight hemicelluloses and degraded cellulose. The percent of alkali-soluble material increases as the wood decays (48). The extraction is done in a water bath maintained at 100 °C. 

Wood Solubility. The solubility of wood in various solvents is a measure of the extraneous components content. No single solvent is able to remove all of the extraneous materials. Ether is relatively nonpolar and extracts fats, resins, oils, sterols, and terpenes. Ethanol/ benzene is more polar and extracts most of the ether-solubles plus most of the organic materials insoluble in water. Hot water extracts some inorganic salts and low molecular weight polysaccharides including gums and starches. Water also removes certain hemicelluloses such as the arabinogalactan gum present in larch wood see Table I). 

Azeotropic distillation involves either an embedded azeotrope, present in the feed mixture, or a contrived azeotrope, formed by the addition of an extraneous component called an entrainer. Benzene-water may be separated into high-purity benzene and the benzene-water azeotrope this is frequently practiced to remove water from benzene when very dry benzene is needed for chemical processing. More commonly encountered are distillation separations that are enhanced through the addition of an entrainer to form an azeotrope. Perhaps the best known separation of this type is the production of anhydrous ethanol from the ethanol-water azeotrope. Here, benzene is added as the entrainer, with the result that a low-boiling ternary azeotrope is formed between benzene, ethanol, and water. This permits the higher-boiling ethanol to be taken from the bottom of the column. The distillate condenses to a heterogeneous mixture of benzene and alcohol-water phases. 

Natural fibers also contain lesser amounts of additional extraneous components includinglowmolecular weight organic components (extractives) and inorganicmatter (ash). Though often small in quantity, extractives can have large influences on... 

Wise L E 1952 Miscellaneous extraneous components of wood. In Wise L E, Jahn E C (eds) Wood chemistry, 2nd ed. Reinhold New York, 644 pp... 

Although water and/or solvent(s) of crystallization are the most common "extraneous lattice components" (hydrates/solvates), many examples demonstrate that stable 3d arrangements/crystal structures can be assembled with the aid of a surprisingly wide variety of "extraneous chemical compounds" (co-crystals). If Nature co-operates in our designs, some choices of "extraneous components" may lead to improved physical and/or biological properties of novel co-crystals. 

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