Apparatus, for continuous extraction

Alternatively, the following procedure for isolating the glycol may be used. Dilute the partly cooled mixture with 250 ml. of water, transfer to a distilling flask, and distil from an oil bath until the temperature reaches 95°. Transfer the hot residue to an apparatus for continuous extraction with ether (e.g.. Fig. II, 44, 2). The extraction is a slow process (36-48 hours) as the glycol is not very soluble in ether. (Benzene may also be employed as the extraction solvent.) Distil off the ether and, after removal of the water and alcohol, distil the glycol under reduced pressure from a Claisen flask. 

Anthracene, 9-chloro-, 43, IS Anthracene, 9,10-dihydro-, 42,48 Apparatus, for continuous extraction, 43, 52... 

Separating funnels for batch extraction special glass apparatus for continuous extraction automatic shakers used for discontinuous counter-current distribution. 

Extraction Apparatus.—Very often an organic substance is so much more soluble in water than in ether and other solvents that shaking with a solvent even when repeated is ineffective. In such cases an apparatus for continuous extraction of solutions is used it should not be wanting in any organic laboratory. The apparatus of Schacherl (Fig. 25), which can be constructed from simple laboratory materials, indicates the principle involved. Still more convenient is the apparatus shown in Fig. 26. It likewise can be constructed in all dimensions from easily obtainable materials. 

Continuous extractions of liquids. When the organic compounds is more soluble in water than in the organic solvent (i.e. the distribution coefficient between the organic solvent and water is small), very large quantities of organic solvent must be employed to obtain even a moderately efficient extraction. This may be avoided by the use of an apparatus for continuous extraction where only relatively small volumes of solvent are required. 

The ratio of the amount extracted to the amount remaining is called the distribution ratio. There are many situations in which the distribution ratio is low, which would require large amounts of solvent if separatory funnels were used exclusively. This can be very expensive in both chemical and labor costs, and the additional cost of solvent disposal is now often prohibitive. Continuous extractors, in which a small volume of solvent is used to extract a portion of the compound, then evaporated, condensed, and used again, are an ideal solution. This process can be repeated for days if necessary and at the end, there is only a small volume of solvent to remove and dispose of Continuous extractors that involve solvents both heavier and lighter than water are discussed in Chapter 10. A widely used apparatus for continuously extracting components from solids is the batch extractor developed by Soxhiet. The sample is placed in a porous paper thimble and then placed in a horizontal tube with a closed bottom. The extraction solvent is dripped onto the top of the solid, percolates through it, and siphons off after a short time, the process is repeated as often as necessary. Soxhiet extraction is covered in Chapter 10. 

Fig. 19. Apparatus for continuous extraction of hash oil. Thin tubing brings the mixture of cannabinoids in solvent from the first pressure cooker in the background through the top of the second cooker which is painted black to absorb heat. Heat lamps are used to evaporate the solvent which rises through the insulated plastic pipe. The DEA stated that this apparatus produced 2.5 quarts of oil from about 82 pounds of marijuana in one hour. The time is unquestionably too short, but if the other figures are correct and grass with 1% THC content was used, the oil would contain about 20% THC. (Reprinted from Drug Enforcement, 1973.)...

Figure 2.2-3 Flow diagram of apparatus for continuous extraction from solids [7]. a magnetic stirrer, feed vessel, c membrane pump, d buffer vessel, e, f preheater (28 mL), g extraction pipe (38 mL), h cooler, i flask, j CO2 meter, k evacuated glas vessel.

Another apparatus for continuous extraction consists of three inverted 250 ml volumetric flasks. A vibratory mixer is used for vigorous shaking of all three flasks. A 101 sample can be siphoned through the apparatus in 4h and extracted, with a total solvent volume of 10 ml.The advantage is that no concentration step is involved. 

If the distribution coefficient is sufficiently large, the simplest approach to liquid-liquid extraction is shaking the sample with an appropriate amount of an organic solvent. With smaller distribution coefficients or large sample volumes, continuous extraction or countercurrent extraction is required to achieve a complete separation. The apparatus for continuous extraction causes a liquid immiscible with the sample solution to circulate continuously and in finely divided form through the sample [171]-[173]. Extracted analytes are concentrated by distillation at appropriate times between individual extraction cycles. 

To about 2-5 g, accurately weighed, in a beaker add 0 5 g of kaolin and mix. Add 5 ml of 70 per cent ethanol and stir thoroughly add a further 45 ml of ethanol and stir again. Filter through a fluted open-texture filter paper, transferring the precipitate to the filter with the aid of further portions of ethanol. Place the filter paper and precipitate in an extraction thimble, transfer to an apparatus for continuous extraction... 

---