Intermediate Topic 903 of 1102 Analytical, Lab & Spectroscopy
Solvent Extraction
Separating compounds based on different solubility in immiscible solvents.
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In-depth explanation of Solvent Extraction
Solvent extraction separates a solute by distributing it between two immiscible liquids, usually water and an organic solvent, in a separatory funnel. The solute partitions between the two phases according to its partition coefficient, the ratio of its concentrations in each phase at equilibrium. Several small portions of extracting solvent remove more solute than one large portion of the same total volume, because each extraction approaches a fresh equilibrium. Acid-base extraction uses pH to convert acids and bases into water-soluble salts, allowing neutral, acidic and basic compounds to be separated. After separation the organic layer is dried and the solvent evaporated to recover the product. Emulsions that form during shaking are broken by adding brine.
Going deeper: Solvent Extraction
Key ideas: Partition coefficient K = C(organic)/C(aqueous). With n extractions of volume V each, the fraction left in water is (V_w/(V_w + K V))^n, so three 10 mL portions beat one 30 mL portion. The organic solvent must be immiscible with water, dissolve the solute, and be easy to remove, and its density decides which layer is on top. Vent the funnel frequently.
Common mistakes and connections: Students forget to vent, which builds pressure, or discard the wrong layer, so keep both until the product is secured. Dichloromethane is denser than water and ether is lighter. Shaking too hard creates emulsions. Ionized solutes stay in water, so adjusting pH is the key to moving acids and bases between layers. Related to acid-base chemistry, solubility and chromatography.
Visualization of Solvent Extraction
For K = 5 and 100 mL of aqueous solution, three 30 mL portions of organic solvent leave less solute behind (6.4 percent) than one 90 mL portion (18.2 percent). The interactive lesson shows this as a live animation or chart.
Worked example and use case
Caffeine is extracted from an aqueous tea solution using dichloromethane.
Frequently asked questions about Solvent Extraction
What is Solvent Extraction?
Separating compounds based on different solubility in immiscible solvents.
Is Solvent Extraction a beginner, intermediate or advanced topic?
Solvent Extraction is a intermediate topic in Analytical, Lab & Spectroscopy. It builds on the vocabulary of beginner topics in this area.
What should I learn before Solvent Extraction?
Study these earlier topics in Analytical, Lab & Spectroscopy first: Steam Distillation, Crystallization, Recrystallization.
What comes after Solvent Extraction?
The next topics in Analytical, Lab & Spectroscopy are Paper Chromatography and Thin Layer Chromatography.
Can I practise Solvent Extraction with quizzes?
Yes. The interactive lesson includes a self-check question on Solvent Extraction, and the Analytical, Lab & Spectroscopy quiz draws on every topic in this area.
Where Solvent Extraction fits in Analytical, Lab & Spectroscopy
Solvent Extraction is topic 27 of 99 in Analytical, Lab & Spectroscopy.