Continuous extractors Soxhlet extractor

Copper(I) iodide, purchased from Fisher Scientific Company, was purified by continuous extraction with anhydrous tetrahydrofuran in a Soxhlet extractor for approximately 12 hours in order to remove colored impurities. The residual copper(I) iodide was then dried under reduced pressure at 25° and stored under nitrogen in a desiccator. 

Figure 8.6 Apparatus used for saeple preparation involving solvent extraction. A, heavier-than-water continuous liquid-liquid extractor B, pressurized Soxhlet extractor for use with supercritical fluids C, Kudema-Danlsh evaporative concentrator 0, autonated evaporative concentrator.

A solid-liquid extraction is the selective dissolution of a component of a solid material through contact with a liquid solvent. Two methods of accomplishing this are 1) shaking the solid with the solvent in the same container for a specified period of time, and 2) using a Soxhlet extractor, in which fresh solvent is continually cycled through the solid for a specified period of time. 

A single solvent probably will not have all the characteristics necessary for optimum resin cleaning. If a mixture of solvents is chosen for use in either the traditional Soxhlet extractor or the Environmental Protection Agency continuous extractor (8), the mixture must also form an azeotrope because both devices recycle their solvents by using distillation. 

The Soxhlet extractor (figure 8.4) is filled with fine grains of one of the two kinds of rock which are most common on the earth s surface, viz. basalt and granite. Next water is constantly passed through this rock mass and for a very long time. This results in a continuous extraction of materials from the rock in other words the rock is exposed to... 

Initial Extraction Technique Continuous extraction apparatus was employed, including an extractor designed to contain the starting plant materials, a distillation flask to hold the solvent mixture, the flask being equipped with a reflux condenser, a drip device to facilitate the removal of the volatilized mixture from the condenser and to percolate it through the continuous extractor, and a Soxhlet type return. Means for heating the continuous extraction system were provided. 

TetramethyIisoindole (6 g, 34.6 mmole) and cobalt powder (30 g, 0.51 mole) are mixed and loaded into a Carius tube (4 X 35 cm volume about 450 mL). After it is evacuated and sealed, the tube is placed in a shielded oven preheated to 390° and heated at this temperature for 4 hours. After the tube is cooled, the dark-blue (or black) powder is placed in a Soxhlet extractor and extracted with pentane (300 mL) until a red-brown impurity is removed (about 24 hours). The pentane is replaced by toluene (300 mL), and extraction is continued until the extract (initially green) is colorless (about 8 hr). Finally, pyridine (300 mL) is used to extract (Soxhlet extractor) the porphine, which requires about 10 hours. The pyridine solution is concentrated to 20 mL, and 100 mL of hexane is added. The precipitate is collected, washed with hexane, and dried overnight in vacuum at 60°, to give [octamethyltetrabenzoporphinato-(2-)] cobalt(II). Yield 2-3 g (35-55%). Anal. Calcd. for C44H36N4Co C, 77.79 H, 530 N, 8.24. Found C, 77.87 H, 5.40 N, 8.48. 

An air-dried wood sample is ground successively in a Wiley mill and a vibrational mill to pass an 80-mesh screen (Note 1) The wood meal is extracted continuously with benzene-ethanol (2 1, v/v) in a Soxhlet extractor for 48 h The extracted sample is first air-dried and then dried over P2Os under vacuum for at least one week to completely remove the moisture A moisture-free sample is required for the NE reaction since boron trifluoride will be deactivated to some extent by any residual moisture in the sample... 

Four types of extraction procedures are employed in these analyses depending on the sample matrix. Chemical waste samples are extracted by refluxing with a Dean Stark water separator. Fly ash samples and soil/sediment samples are extracted in a combination of a Soxhlet extractor and a Dean Stark water separator. Water samples are filtered and then the filtrate is extracted using either a separatory funnel procedure or a continuous liquid-liquid extraction procedure. The filtered particulates are extracted in a combination of a Soxhlet extractor and a Dean Stark water separator. 

Extraction. The explosive is extracted with pure dry ether in a Soxhlet extractor or a Gooch crucible (preferably in a continuous... 

Soxhlet extractor. A laboratory apparatus consisting of a glass flask and condensing unit used for continuous reflux extraction of alcohol- or ether-soluble components of food products. Named after its inventor, a German chemist. 

Continuing to exclude all air and water, the residue is loaded into a Soxhlet extractor. All joints are fitted with Teflon sleeves. The residue is extracted with pentane (150 mL) for 2 days or until the residue becomes white and the solution is reddish brown. The volatiles are removed from the solution to afford the product as a brown solid in 66% yield (3.2 g). mp 80-82°C. 

Assemble the apparatus as shown in Fig. 14.5, clamping at the joints at the flask and the top of the Soxhlet extractor. The best heat source to use for continuous operation over a long period is a mantle. 

The apparatus for Soxhlet extraction is shown in Fig. 14.5 and comprises a flask containing the solvent, a Soxhlet extractor and a reflux condenser (p. 116). The solid to be extracted is placed in a porous thimble, made from hardened filter paper, and the solvent is heated so that its vapour flows past the thimble, condenses and fills the extractor with hot solvent to extract the solid. When the extractor is full, the solvent (together with the extracted material) siphons back into the solvent flask and the process is repeated automatically. The advantage of this procedure is that fresh solvent continually extracts the solid, which is concentrated in the flask. The disadvantage is that the compound extracted is kept at the boiling point of the solvent for a prolonged period. Soxhlet extractors come in sizes of 10 mL to 5000 mL, based on the volume of solvent contained in the extractor. The procedure for using a Soxhlet extraction system is described in Box 14.2. 

Frequently it is possible to extract the volatile components directly from the intact food or plant material. This is particularly true with thin materials such as leaves or relatively dry powders such as ground coffee, tea or wheat flour. More often it is necessary to drop or grind the material in some way (e.g. with a blender) to put it into a finely divided form. Sometimes with dry materials a Soxhlet apparatus is used (5). With highly aqueous materials such as fruits and vegetables, a continuous liquid-liquid extractor can be used (on the blended filtered product). 

Fibers 10 cm long were extracted in a Soxhlet extractor for 1 hr with thiophene-free benzene and then air dried. They were then soaked in distilled water adjusted to pH 5 with HCl the water was changed frequently and the soaking was continued until the pH of the water remained constant. This treatment was carried out in an effort to assure that all exchangeable cations within the fiber were hydrogen ions at the start of the experiment. 

The solid-solvent mixture is stirred or shaken and then filtered or centrifuged to separate the matrix. Typically three extractions, using small portions of solvent, are needed to assure quantitative extraction. Heating may help in some cases. Or ultrasonic energy (ultrasonic batch or ultrasonic probe) can be used to increase efficiency. Continuous Soxhlet extraction is often used. A Soxhlet extractor has a round-bottom distillation pot, with a porous thimble above it in a siphon chamber, into which the sample is placed. Solvent is continuously cycled through the sample by distilling the solvent to a condenser centered over the thimble. The condensed solvent permeates through the matrix and the thimble, and is siphoned back into the pot, where it is recycled. The extracted material is concentrated in the pot. 

Several examples of aldol addition and condensation are given in Scheme 7.3. Entries 1 and 2 are typical aldol reactions of aldehydes, with and without dehydration. The reaction in Entry 1 was done with 15% KOH in aqueous solution at room temperature. The condensation reaction in Entry 2 was carried out at 80°-90°C with 1M NaOH. Entries 3 and 4 show addition and condensation reactions of acetone. Entry 3 features a clever way of overcoming the unfavorable equilibrium of the addition step. The basic catalyst is contained in a separate compartment of a Soxhlet extractor. Acetone is repeatedly passed over the basic catalyst by distillation and the condensate returns to the flask. Since there is no catalyst present in the flask, the adduct remains stable. The concentration of the addition product builds up as the more volatile acetone distills preferentially. The acid-catalyzed condensation in Entry 4 is carried out similarly. The acetone is continuously passed over the acidic resin, and the reaction is driven forward by the stability of the conjugated condensation product. In Entry 5, the final product is a (3-chloroketone, presumably formed by addition of HCl to a dehydrated intermediate. 

Thermal decomposition of the carbonyl anion was promoted by refluxing the solution 1 hr during this time a dark microcrystalline solid precipitated. The black solid was isolated by filtration and placed in a Soxhlet extractor with 1,2-dichloroethane. After two weeks of continuous extraction, virtually all of the solid had passed through the frit 4.87 grams of recrystallized solid were isolated from the solution in the extraction flask by filtration. Analysis for [(C4H9)4N]2Mo4lioCl calcd Mo 17.66, I 58.40, Cl 1.63, C 17.68, H 3.34, N 1.29 found Mo 17.72, 1 58.25, Cl 1.53, C 18.08, H 3.32, N 1.46. 

Extraction of organic analytes such as pesticides, PCBs, and fats from solid samples such as food, soil, plants, and similar materials can be done using a Soxhlet extractor. A Soxhlet extractor consists of a round bottom flask fitted with a glass sample/siphon chamber in the neck of the flask. On top of the sample chamber is a standard water-cooled condenser. The solid sample is placed in a cellulose or fiberglass porous holder, called a thimble the solvent is placed in the round bottom flask. Using a heating mantle around the flask, the solvent is vaporized, condensed, and drips or washes back down over the sample. Soluble analytes are extracted and then siphoned back into the round bottom flask. This is a continuous extraction process as long as heat is applied. The extracted analyte concentrates in the round bottom flask. 

The most common means for exhaustive extraction of solid material is via a soxhlet extraction apparatus. These devices, are analogous to the continuous extractors... 

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