Differential Extraction

Differential extraction, or solvent extraction, is used to recover an organic compound from an aqueous solution by shaking it with an immiscible organic solvent such as ether or chloroform in a separating funnel. The method depends on the fact that the compound distributes itself between the two immiscible layers according to its relative solubility, governed by the distribution (partition) law. The compound passes preferentially into the layer in which it is more soluble; since most organic compounds are more soluble in organic solvents than in water, they move into the organic layer, which is then separated and evaporated to recover the compound. The statement about reaction to form a salt is wrong because extraction is a physical partitioning process, not a chemical reaction. Identical densities with complete mixing is incorrect because the method requires two immiscible layers of different densities that separate cleanly. Oxidation by the solvent is not involved at all. Repeated extraction with small portions of solvent is more efficient than one large portion, a point emphasised in NCERT. Plausibility check: separation is possible only because the solute prefers one phase, consistent with the partition principle.