Fractional extent

Absolute bioavailability (extent) = fraction of drug absorbed (F) ... 

Fractionating technologies are now upcoming for many biotechnological separation systems. The best-developed methodologies are continuous (resin-Uquid) chromatography and extraction [ 14-16], and to a smaller extent, fractional crystallisation and membrane-aided separations [17,18]. 

Since 1952, most of the tritium measured in the atmosphere originates from thermonuclear explosions. Like hydrogen, deuterium and tritium also exhibit molecular isomerism. Because of the important differences between the relative atomic masses of the three isotopes, their physical properties (e.g., density, enthalpy of vaporization) differ greatly. This allows an easier isotopic separation than for any other element. Several separation processes are used for the enrichment and separation of hydrogen isotopes. Most of these processes use isotopic exchange reactions (e.g., H D-H O or NH3-HD) and to a lesser extent fractional distillation and water electrolysis (e.g., Norway, Canada). 

An important feature of the Arctic Ocean is its floating sea-ice cover that has traditionally ranged from 16 million km in March to a minimum coverage of 7 million km at the end of summer melt season on September. Based on regression analysis during the period between 1979 and 2006, the ice extent (fractional ice cover) has declined every month. The decline is the largest during September with a retreat of 8.6 2.9% per decade or approximately 10,000 km per year (Serreze et al. 2007). 

Theorem.- In a linear mechanism in pseudo-steady state modes, extents, fractional extents, speeds or rates are identical whatever the principal component of the total reaction chosen for their definitions. 

The experiment aims to derive a number of kinetic properties, such as the extent, fractional extent and speed (speed, specific speed or rate), which are not directly measurable. The results are grouped into two families ... 

Figure A2.5.3. Typical liquid-gas phase diagram (temperature T versus mole fraction v at constant pressure) for a two-component system in which both the liquid and the gas are ideal mixtures. Note the extent of the two-phase liquid-gas region. The dashed vertical line is the direction x = 1/2) along which the fiinctions in figure A2.5.5 are detemiined.

Ethyl acetoacetate decomposes slightly (with the formation of dehydracetio acid C,H,0,) when distilled at atmospheric pressure. The extent of decomposition is reduced if the distillation is conducted rapidly. The b.p, is 180°/760 mm. and a 6° fraction should be collected. Normal pressure distillation is not recommended if a pure product is desired. 

Gr. neos, new) Discovered by Ramsay and Travers in 1898. Neon is a rare gaseous element present in the atmosphere to the extent of 1 part in 65,000 of air. It is obtained by liquefaction of air and separated from the other gases by fractional dishhation. 

Gr. neos, new, and didymos, twin) In 1841, Mosander, extracted from cerite a new rose-colored oxide, which he believed contained a new element. He named the element didymium, as it was an inseparable twin brother of lanthanum. In 1885 von Welsbach separated didymium into two new elemental components, neodymia and praseodymia, by repeated fractionation of ammonium didymium nitrate. While the free metal is in misch metal, long known and used as a pyrophoric alloy for light flints, the element was not isolated in relatively pure form until 1925. Neodymium is present in misch metal to the extent of about 18%. It is present in the minerals monazite and bastnasite, which are principal sources of rare-earth metals. 

It is convenient to define the fraction of reacted functional groups in a reaction mixture by a parameter p, called the extent of reaction. Thus p is the fraction of A groups which have reacted at any stage of the process, and 1 - p is the fraction unreacted ... 

Note that N /N gives the mole fraction of n-mers in a mixture at an extent of reaction p. As we have seen before, N = (1 - p) Aq, since each molecule in the mixture contains one unreacted A group. Incorporating this result into Eq. (5.25) yields... 

As with other problems with stoichiometry, it is the less abundant reactant that limits the product. Accordingly, we define the extent of reaction p to be the fraction of A groups that have reacted at any point. Since A and B groups... 

The extent of reaction p is again based on the group present in limiting amount. For the system under consideration, p is the fraction of A groups that have reacted. 

Figure 7.8 Mole fractions styrene (Mj) and methyl methacrylate (M2) in feedstock (f) and copolymers (F) as a function of the extent of polymerization. Average copolymer compositions are also shown. [From V. E. Meyer and R. K. S. Chan, Polym. Prepr. 8 209(1967), used with permission.]...

Fractional crystallization may be accompHshed on a batch, continuous, or semicontkiuous basis. Oil is chilled continuously while passkig through the unit and is then passed over a continuous belt filter which separates soHd fat from the Hquid oil. The process gives poorer separation compared to solvent fractionation because oils are viscous at crystallization temperatures and are entrained to a significant extent ki the soHd fraction. The Hquid fraction, however, is relatively free of saturated material. 

The fraction of open cells expresses the extent to which the gas phase of one cell is in communication with other cells. When a large portion of cells are intercoimected by gas phase, the foam has a large fraction of open cells, or is an open-ceUed foam. Conversely, a large proportion of noninterconnecting cells results in a large fraction of closed cells, or a closed-ceUed foam. 

Montedison and Mitsui Petrochemical iatroduced MgCl2-supported high yield catalysts ia 1975 (7). These third-generation catalyst systems reduced the level of corrosive catalyst residues to the extent that neutralization or removal from the polymer was not required. Stereospecificity, however, was iasufficient to eliminate the requirement for removal of the atactic polymer fraction. These catalysts are used ia the Montedison high yield slurry process (Fig. 9), which demonstrates the process simplification achieved when the sections for polymer de-ashing and separation and purification of the hydrocarbon diluent and alcohol are eliminated (121). These catalysts have also been used ia retrofitted RexaH (El Paso) Hquid monomer processes, eliminating the de-ashing sections of the plant (Fig. 10) (129). 

Ced rwood. Many varieties of cedarwood oil are obtained from different parts of the world. They are produced mainly by steam distillation of chipped heartwood, but some are also produced by solvent extraction. The oils, which vary significantly ia chemical composition, are used ia perfumes as such, but the main uses are as distillation fractions and chemical derivatives. For the latter purposes the most used oils, which are similar ia composition, are from Texas ia the United States (Juniperus mexicand) and from China Cupressusfunebris). The principal constituents of these oils are cedrene [11028-42-5] (4), thujopsene [470-40-6] (5), and cedrol [77-53-2] (6). The first two of these are obtained together by distillation and used mostiy ia the form of acetylated derivatives. Cedrol is used as such and, to a greater extent, as its acetate ester. 

The early developments of solvent processing were concerned with the lubricating oil end of the cmde. Solvent extraction processes are appHed to many usefiil separations in the purification of gasoline, kerosene, diesel fuel, and other oils. In addition, solvent extraction can replace fractionation in many separation processes in the refinery. For example, propane deasphalting (Fig. 7) has replaced, to some extent, vacuum distillation as a means of removing asphalt from reduced cmde oils. 

Polyester resins can also be rapidly formed by the reaction of propylene oxide (5) with phthaUc and maleic anhydride. The reaction is initiated with a small fraction of glycol initiator containing a basic catalyst such as lithium carbonate. Molecular weight development is controlled by the concentration of initiator, and the highly exothermic reaction proceeds without the evolution of any condensate water. Although this technique provides many process benefits, the low extent of maleate isomerization achieved during the rapid formation of the polymer limits the reactivity and ultimate performance of these resins. 

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