Extractions fractionation stages

Should the extraction be continued until substantial equilibrium between the phases occurs, then the material balance equation (7) shows that the concentrations in the liquids move along line AB extended until the equilibrium curve is reached at C, giving rise to the ultimate equilibrium concentrations xe and ye. A fractional stage efficiency E may then logically be defined (T3) as the ratio of the number of moles N of solute actually transferred in an extraction to Ne, the moles which would be transferred should equilibrium be reached ... 

Concentration of solute in the extract exiting stage moles/volume Concentration of the solute in the entering solvent, moles/volume Molar fraction of the solute in the solution, or the solubility... 

The sequential extraction procedure consists of three (main) stages, plus a final (residual fraction) stage (Figure 5.20), as follows ... 

Sequential extraction A multistage chemical extraction in which the residual fraction of early stages, becomes the extractable fraction for later stages. 

Biochemical analyses can be performed in parallel with or instead of morphological studies. At various time points during the course of in vitro disassembly, aliquots of the reaction mixture should be separated into supernatant and pellet fractions by sedimentation at 12,000 g and proteins subjected to SDS-PAGE and immunoblot analysis. An extract of stage 14 Drosophila oocytes contains only lamin Dm i, (Smith and Fisher, 1989 see also Lin and Fisher, 1990 Mans et at., 1995). Purified Drosophila nuclei contain lamins Dmi and Dm2 (Smith et al, 1987 see also Lin and Fisher, 1990 Maus et al, 1995). Lamin Dmmit migrates with a gel mobility intermediate to lamins Dm, and Dm2 (Fig. 4). 

The extraction of titanium is still relatively costly first the dioxide Ti02 is converted to the tetrachloride TiCl4 by heating with carbon in a stream of chlorine the tetrachloride is a volatile liquid which can be rendered pure by fractional distillation. The next stage is costly the reduction of the tetrachloride to the metal, with magnesium. must be carried out in a molybdenum-coated iron crucible in an atmospheric of argon at about 1100 K ... 

Place 80 g, of hydroxylamine sulphate (or 68-5 g. of the hydrochloride), 25 g. of hydrated sodium acetate, and 100 ml. of water in a 500 ml. flask fitted with a stirrer and a reflux water-condenser, and heat the stirred solution to 55-60°. Run in 35 g (42 nil,) of -hexyl methyl ketone, and continue the heating and vigorous stirring for ij hours. (The mixture can conveniently be set aside overnight after this stage.) Extract the oily oxime from the cold mixture twice with ether. Wash the united ethereal extract once with a small quantity of water, and dry it with sodium sulphate. Then distil off the ether from the filtered extract, preferably using a distillation flask of type shown in Fig. 41 (p. 65) and of ca, 50 ml, capacity, the extract being run in as fast as the ether distils, and then fractionally distil the oxime at water-pump pressure. Collect the liquid ketoxime, b.p. 110-111713 mm. Yield, 30-32 g. 

Dual solvent fractional extraction (Fig. 7b) makes use of the selectivity of two solvents (A and B) with respect to consolute components C and D, as defined in equation 7. The two solvents enter the extractor at opposite ends of the cascade and the two consolute components enter at some point within the cascade. Solvent recovery is usually an important feature of dual solvent fractional extraction and provision may also be made for reflux of part of the product streams containing C or D. Simplified graphical and analytical procedures for calculation of stages for dual solvent extraction are available (5) for the cases where is constant and the two solvents A and B are not significantly miscible. In general, the accurate calculation of stages is time-consuming (28) but a computer technique has been developed (56). 

Ca.rhona.tlon, GalHum can be extracted by fractional carbonation which consists of treating the aluminate solution with carbon dioxide in several controlled stages. This process is no longer under industrial operation (6). 

In typical processes, the gaseous effluent from the second-stage oxidation is cooled and fed to an absorber to isolate the MAA as a 20—40% aqueous solution. The MAA may then be concentrated by extraction into a suitable organic solvent such as butyl acetate, toluene, or dibutyl ketone. Azeotropic dehydration and solvent recovery, followed by fractional distillation, is used to obtain the pure product. Water, solvent, and low boiling by-products are removed in a first-stage column. The column bottoms are then fed to a second column where MAA is taken overhead. Esterification to MMA or other esters is readily achieved using acid catalysis. 

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