Extraction total reflux

Figure 14.7. Locations of operating points P and Q for feasible, total, and minimum extract reflux on triangular diagrams, and stage requirements determined on rectangular distribution diagrams, (a) Stages required with feasible extract reflux, (b) Operation at total reflux and minimum number of stages, (c) Operation at minimum reflux and infinite stages.

Total thiamine Rice Extraction by refluxing Analytical Zorbax Isocratic phosphate- Online postcolumn derivati- External standardization. 77... 

The solvent extraction of rare-earth nitrates into solutions of TBP has been used commercially for the production of high-purity oxides of yttrium, lanthanum, praseodymium and neodymium from various mineral concentrates,39 as well as for the recovery of mixed rare-earth oxides as a byproduct in the manufacture of phosphoric acid from apatite ores.272 273 In both instances, extraction is carried out from concentrated nitrate solutions, and the loaded organic phases are stripped with water. The rare-earth metals are precipitated from the strip liquors in the form of hydroxides or oxalates, both of which can be calcined to the oxides. Since the distribution coefficients (D) for adjacent rare earths are closely similar, mixer—settler assemblies with 50 or more stages operated under conditions of total reflux are necessary to yield products of adequate purity.39... 

In Table 10.8, R decreases with the increase in F according to Equation 10.2. The operation time decreases and the productivity increases with the increase in F . These are as expected. Initial total reflux operation was not needed for any case. Significant improvement in productivity (about 77%) is noted for case 4 compared to the base case. This clearly reveals the importance of extractive distillation for... 

Some laboratories employ operationally defined procedures to extract total elements from soils, such as a one hour reflux with a mixture of boiling nitric and hydrochloric acids. Such an approach may be adequate, for example, to study the build up of elements such as zinc, cadmium, copper, lead, and nickel in sludge-treated soils. However, operationally defined procedures are much more often used to extract the portions of elements present in soils and sediments in a labile or plant-available form. For example, solutions of EDTA or CDTA may be used to extract copper, zinc, manganese, and iron from soils,17 or hydroxylamine hydrochloride may be used to extract easily reducible manganese or manganese oxide-bound trace elements.6... 

Acetone and methanol are impossible to separate by simple distillation due to the presence of an azeotrope. However, the addition of water near the top of a column allows these two components to be separated. Five sets of steady-state operating data for the extractive distillation of an acetone-methanol azeotrope in a laboratory scale column have been provided by Kumar et al. (1984). A schematic diagram of the column is provided in Figure 14.19. The column had a diameter of 15 cm and was fitted with 13 bubble cap trays, a total condenser and a thermosiphon (equilibrium) reboiler. Unlike many experimental distillation studies, these experiments were not carried out at total reflux the acetone-methanol feed entered the column on the eleventh stage from the top (the condenser counts as the first stage) and the water was introduced on stage six. The column was operated at atmospheric pressure for all five runs. Additional details of the column, operational specifications, and computed product compositions for one of these experiments can be found in Table 14.9. 

Minimum reflux corresponds to the overlap of an operating line and a tie-line (infinite stages at a pinch point). This concept is similar to minimum solvent flowrate for an extraction process without reflux. Total reflux corresponds to the minimum number of stages. Remember that total reflux means that no streams are going into or out of the column, so that F, B, and D are zero, and A = A. ... 

A solution of NaOMe (9.2 mL) prepared from Na (0.5 g) and MeOH (50 mL) was added to an ice-cold solution of6-chloropteridine (0.66 g, 4.0 mmol) in MeOH (25 mL). The mixture was kept at 20°Cfor 30 min then neutralized with a stream of C02. The solvent was removed under reduced pressure, and the residue was repeatedly extracted with light petroleum (bp 60-80°C) (total of 300 mL). The extract was refluxed with charcoal, filtered, then concentrated to 50 mL when the product crystallized yield 0.34 g (53%) mp 124-125 C. 

Powdered drug (0.5-1 g) is extracted under reflux for approximately 15 min with 5 ml 50% methanol. The hot extract is filtered and the filter then wa.shed with methairol up to a total of 5.0 ml 20-30 [d is used for TLC. 

Dissolution of the powder. After homogenising the powder, obtained either directly by drilling or by cmshing core shces, a part is weighed precisely and dissolved in a constant amount of liquid, most frequently in concentrated nitric acid solution with ISA (ionic strength adjuster). In this way the total or acid soluble chloride content is determined. The dissolution process is the most important step determining the reproducibility of the chloride analysis. Alternatively, the Soxhlet extraction technique (reflux of boiling water on the concrete powder for 24 h) is used to dissolve chloride ions. Both methods result in a similar total chloride content. 

The total ionic content and the amounts of specific metal ions such as sodium and potassium greatly affect the electrical properties of an insulative adhesive and of the electronic function of a circuit. A simple test to determine the total ionic content of a polymeric material is to digest a weighed, powdered sample in deionized water and to measure the resistivity of the water extracts after refluxing for 20 hours. This test gives a rough idea of the extent of ionic contaminants in the sample. For example, a drop in resistivity from 10 MQ-cm to 10,000 Q-cm indicates a considerable amount of ionic species. The total ionic content is reported as ppm of equivalent NaCl ... 

A7. What situation in countercurrent extraction is superficially analogous to total reflux in distillation How does it differ ... 

Total lipid content. There are physical and chemical procedures for oil/fat estimation. In physical procedures, lipids are not isolated and samples are used directly, and lipids are estimated by nuclear magnetic resonance (NMR) spectroscopy. In chemical procedures, lipids are extracted by refluxing the sample in suitable solvents (like petroleum ether) by using standard methods (AOAC or AOCS). Different classes of lipids such as neutral lipids (by nonpolar solvents such as petroleum ether, hexane), phospho- or glycolipids (by polar solvents such as methanol) can be extracted and used for... 

Total Reflux. For the least number of stages, corresponding to total reflux or infinite reflux ratio, no raffinate product or extract product is withdrawn from the plant. To maintain the material balance, F and consequently the capacity of the plant must be zero. Rn = Rny Ro —... 

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