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actinoid elements

In actinoid element: Oxidation states +3 and +4
…used to effect separation, and solvent extraction, in which specific nonaqueous solvents and complexing reagents are used to withdraw the desired element from aqueous solution.
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chemical separation

In chemical analysis: Extraction
solubilities of solutes in immiscible solvents. If the solutes are in an aqueous solution, an organic solvent that is immiscible with water is added. The solutes will dissolve either in the water or in the organic solvent. If the relative solubilities of the solutes differ in the two solvents, a…
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extraction and processing

In metallurgy: Recovery
Solvent extraction combined with electrolytic deposition takes dilute, low-value metal solutions and concentrates them into small volumes and high metal contents, rendering them satisfactory for electrolytic treatment. Low-grade copper ores are processed in this manner. First, a large volume of a low-value copper leach solution…
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food processing

In fat and oil processing: Solvent extraction
Cakes obtained by pressing operations still retain 3 to 15 percent of residual oil. When the value of the oil is considerably greater as oil than as a part of the meal, it is desirable to obtain more complete extraction with solvents.…
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petroleum refining

In heavy oil and tar sand: Solvent extraction
Solvent extractions also have been used to recover heavy oils. In this process a solvent or emulsifying solution is injected into a heavy oil reservoir. The fluid dissolves or emulsifies the oil as it advances through the permeable reservoir. The oil and fluid…
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In petroleum refining: Solvent extraction
Solvent extraction processes are employed primarily for the removal of constituents that would have an adverse effect on the performance of the product in use. An important application is the removal of heavy aromatic compounds from lubricating oils. Removal improves the viscosity-temperature relationship…
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soybean oil recovery

In origins of agriculture: The soybean
Development of the solvent process of extracting soybean oil has greatly increased the yield. A 60-pound bushel of soybeans processed by this method yields 10 1/2 pounds of oil and 45 pounds of meal. Soybean meal and cake are used chiefly for livestock feed in the United…
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thorium purification

In thorium processing: Acidic and alkaline digestion
…acid for final purification by solvent extraction.
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uranium leaching

In uranium processing: Treatment of uranium leachates
…from acidic ore leach-liquors through solvent extraction. In industrial methods, alkyl phosphoric acids—e.g., di(2-ethylhexyl) phosphoric acid—and secondary and tertiary alkyl amines are the usual solvents. As a general rule, solvent extraction is preferred over ion-exchange methods for acidic leachates containing more than one gram of uranium per litre. Solvent extraction…
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countercurrent distribution

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countercurrent distribution

chemistry

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countercurrent distribution, in chemistry, a multistage solvent-extraction process, one of many separation methods that can be employed in chemical analysis.

Substances are separated by this method on the basis of their different solubilities in two immiscible liquids. These two liquids, flowing in opposite directions, are brought into contact, mixed, and allowed to separate. The upper layer is transferred off in one direction and the lower in another; this cycle of operations may be repeated as many times as necessary to effect the desired separation.

A sample of a substance in contact with two solvents that do not dissolve in one another seeks an equilibrium condition in which it is distributed between them; the ratio of the concentrations in the two solvents, called the distribution coefficient, is characteristic of the compound and of the solvent pair. Compounds that have dissimilar molecular structures usually have widely different distribution coefficients, and mixtures of such compounds can be separated satisfactorily by one or a few transfers between a suitable solvent pair in simple equipment. Closely similar substances, however, such as proteins, have very similar distribution coefficients, and hundreds of transfers may be required to produce a complete separation.

The principle of countercurrent distribution is similar to that of chromatography; both procedures are used for analysis and purification of mixtures of similar compounds.