Decantation is a process for the separation of mixtures of immiscible liquids or of a liquid and a solid mixture such as a suspension. It is a technique that separates components of a mixture based on differences in density. The basic principle of decantation is that heavier (denser) substances sink, while lighter (less dense) substances float. Decantation involves two steps: the lighter component is poured or siphoned off the top of the mixture, or a separatory funnel drains the heavier component.
Decantation can be used to separate immiscible liquids that have different densities. For example, when a mixture of water and oil is present in a beaker, after some time a distinct layer between the two liquids is formed, with the oil layer floating on top of the water layer. This separation can be done by pouring oil out of the container, leaving water behind. Decantation can also separate solid and liquid mixtures by allowing gravity to pull the solid fragments to settle at the bottom of the container. In laboratory situations, decantation of mixtures containing solids and liquids occur in test tubes. To enhance productivity, test tubes should be placed at a 45° angle to allow sediments to settle at the bottom of the apparatus.
Decantation is frequently used to purify a liquid by separating it from a suspension of insoluble particles. For example, in red wine, the wine is decanted from the potassium bitartrate crystals to avoid unsavory taste. This makes the wine more tonic and astringent. Cream accelerates to the top of milk, allowing the separation of milk and cream, which is used in the cheese industry. Fat is determined in butter by decantation.
In summary, decantation is the process of separating a liquid from solid and other immiscible liquids by removing the liquid layer at the top from the layer of solid or liquid below. It is a simple and effective technique that uses gravity to separate components of a mixture based on differences in density.
