What Is a Chemical Method of Separation?
Extraction, distillation, recrystallization and chromatography are different chemical methods of separation. Extraction is useful for separating compounds with different polarities, and distillation is commonly used to purify liquids. Recrystallization is used to purify solids, and chromatography is used to separate compounds and mixtures.
In extraction, a mixture of a polar solvent and a nonpolar solvent is used on a compound. Each solvent dissolves a different part of the compound. By separating each phase of dissolution and then allowing the solvents to evaporate, the different parts of the compound are cleanly separated. Extraction is used to remove solutes from solids.
Distillation separates compounds from liquids through a process of boiling. The vapors that escape from the boiling liquid are collected, and compounds with a lower boiling point are separated from those with a higher boiling point.
Through the process of crystallization, solids are dissolved in a hot sample of solvent. The solution is then cooled until some of it crystallizes. As this process is repeated, the sample becomes more pure.
Chromatography, developed by Russian botanist Mikhail Tsvet in 1906, was first used on plants to separate colored pigments. In chromatography, a gas or liquid flows over a solid. Compounds with an affinity for the solvent are easily carried away, while those with an affinity for the solid move more slowly.