Extraction by chemically active solvents

This type of extraction depends upon the use of a reagent which reacts chemically with the compound to be extracted, and is generally employed either to remove small amounts of impurities in an organic compound or to separate the components of a mixture. Examples of such reagents include dilute (5 per cent.) aqueous sodium or potassium hydroxide solution, 5 or 10 per cent, sodium carbonate solution, saturated sodium bicarbonate solution (co. 5 per cent.), dilute hydrochloric or sulphuric acid, and concentrated sulphuric acid. 

Dilute sodium hydroxide solution (and also sodium carbonate solution and sodium bicarbonate solution) can be employed for the removal of an organic acid from its solution in an organic solvent, or for the removal of acidic impurities present in a water-insoluble solid or liquid. The extraction is based upon the fact that the sodium salt of the acid is soluble in water or in dilute alkali, but is insoluble in the organic solvent. Similarly, a sparingly soluble phenol, e.g., (3-naphthol, C10H7.OH, may be removed from its solution in an organic solvent by treatment with sodium hydroxide solution. 

Dilute hydrochloric or sulphuric acid Ends application in the extraction of basic substances from mixtures or in the removal of basic impurities. The dilute acid converts the base (e.g., ammonia, amines, etc.) into a water-soluble salt (e.g., ammonium chloride, amine hydrochloride). Thus traces of aniline may be separated from impure acetanilide by shaking with dilute hydrochloric acid the aniline is converted into the soluble salt (aniline hydrochloride) whilst the acetanilide remains unaffected. 

Cold concentrated sulphuric acid will remove unsaturated hydrocarbons present in saturated hydrocarbons, or alcohols and ethers present in alkyl halides. In the former case soluble sulphonated products are formed, whilst in the latter case alkyl hydrogen sulphates or addition complexes, that are soluble in the concentrated acid, are produced. 

For the continuous extraction of a solid by a hot solvent, the Soxhlet extraction apparatus, shown in Fig. II, 44, 4, is usually employed. The 

N V tetrachloride. The apparatus of Fig. 11, 44, 2 can easily be adapted for the same purpose by arranging for the 

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Extraction by chemically active solvents. Not infrequently the crude organic product from a reaction may contain a mixture of acidic (phenols and carboxylic acids), basic and neutral components in various combinations. Some of these components may of course be impurities, but none the less, whether as a preliminary purification stage or as a means of separating the mixture, a carefully planned solvent extraction procedure may be adopted using acidic and basic reagents which react chemically with the basic and acidic components of the mixture respectively. The following full account of a typical procedure may be abbreviated in practice according to the complexity of the mixture to be handled. 

Apart from the activation of a biphasic reaction by extraction of catalyst poisons as described above, an ionic liquid solvent can activate homogeneously dissolved transition metal complexes by chemical interaction. 

Extractions and Chemical Analyses of Amaranthus palmerl S. Wats (Amaranthaceae). The plant material for the chemical studies was supplied by Dr. R. M. Menges, USDA, Weslaco, TX. The air-dried aerial parts (518 g) were extracted at ambient temperature with petroleum ether (PE), dichloromethane (CI Clj) and methanol (MeOH) and the solvents were evaporated In vacuo providing 4.5 g, 4.7 g and 12.lg crude extracts, respectively. Samples of the crude extracts were tested by Dr. J. M. Bradow for germination regulation activity and the biological data are described in her paper. 

Protactinium is separated by solvent extraction and anion exchange processes by using sulfate solutions. After chemical separation, the protactinium salts are ignited to a pentoxide, Pa205, which may be converted into an arsenazo(III) complex. The absorbance of the solution is measured at 630 nm with a spectrophotometer. Protactinium-231 is an alpha emitter and also forms photons at 300 KeV, which can be measured by various radioactive counters and spectrophotometric techniques. Protactinium also can be measured by neutron activation analysis. 

Reid and others(11. 121 have shown that supercritical solvents exhibit varying degrees of specificity towards a particular specie. Furthermore, the small number of SC solvents available limits the potential use SC extraction. The use of entrainers or mixtures of solvents, may remove the limitation imposed by the narrow choice of likely solvents. Moreover, it is possible that through the proper choice of entrainer and solvent the desired chemical activity can be adjusted to improve the selectivity of the solvent. For example, mixtures of solvent gases with entrainers can permit a modification of critical properties as well as chemical properties, so that P and T adjustment can be used to maximize some physical property of the system(2). 

Primary recovery of the active ingredient from the solid or liquid phase to remove large quantities of unwanted waste materials, which may themselves be processed further. Suitable techniques include solvent extraction, precipitation by chemical or physical changes to the product-containing solution, and ultrafiltration or microfiltration to separate products above a particular size. Work done on combined biomass separation-primary product recovery processes such as expanded-bed adsorption are now being commercialized in the pharmaceutical industry. 

The valuable fertile elements are recovered from the acid solution by extraction with an organic solvent. The acid residue, containing the extremely radioaetive fission products, is processed to convert the waste into a stable solid form. The fission product waste, in a very concentrated form, is stored for ultimate disposal. This waste represents a different problem than the waste from current burner reactors. Because of the chemical concentration step there is less total mass of material. The same concentration process that reduced the mass of the waste concentrates the radiation produced into a smaller more intense package. This waste is so radioactive that it gets hot and must be actively cooled or diluted to prevent meltdown. Safe storage and disposal methods are very difficult to design. 

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