Extraction

A solvent is added to a liquid or solid sample, and specific substances in the sample are selectively transferred to the solvent phase and separated from other substances. In general, the extraction rate is slow with solids, so continuous extraction using, for example, a Soxhlet extractor is used. Liquid-liquid extraction has an extremely wide range of applications. This is because the original solution and the solvent separate into two phases due to the difference in specific gravity, and because there is a large difference in the distribution coefficient of the solute between the original solution and the solvent, it is concentrated in the solvent. A liquid-liquid system is called liquid-liquid extraction, and a solid-liquid system is called solid extraction or leaching. Liquid-liquid extraction operations include:
(1) The extractant (raw material) phase and the extractant (solvent) phase are mixed and contacted, and the extractant (target component) is transferred into the extractant.
(2) The mixture is allowed to stand and separate into two phases: the raffinate and the extract.
(3) The extract is separated into an extractant and a residue to obtain the target components.
(4) Recovery of the extractant from the raffinate.
The process consists of the following steps. Solid extraction is
(1) A method in which extraction is performed by pouring the extractant into a solid layer (flow-through type),
(2) A method in which the solid is dispersed in an extractant (immersion method),
[See alternative terms] Solvent extraction

Source: Morikita Publishing "Chemical Dictionary (2nd Edition)" Information about the Chemical Dictionary 2nd Edition

液体または固体試料に溶媒を加え，試料中の特定物質を選択的に溶媒相に移してほかの物質より分離すること．一般に，固体では抽出速度が遅いので，たとえばソックスレー抽出器などを用いた連続抽出が採用される．液-液抽出はきわめて広い応用範囲がある．これは原液と溶媒とが，比重差により2相に分離し，溶質の原液と溶媒への分配係数に大きな差があるため，溶媒に濃縮されることによる．液-液系を液-液抽出，固-液系を固体抽出または浸出という．液-液抽出操作は，
(1)抽料(原料)相と抽剤(溶剤)相とを混合接触させ，抽剤中に抽質(目的成分)を移動させる，
(2)その混合液を静置して，抽残液と抽出液の2相に分離させる，
(3)抽出液を抽剤と抽質に分離して目的成分を得る，
(4)抽残液からの抽剤の回収，
などの過程からなる．固体抽出は，
(1)固体層に抽剤を注いで抽出を行う方法(貫流式)，
(2)固体を抽剤中に分散させて抽出する方法(浸漬式)，
の二通りが行われている．[別用語参照]溶媒抽出

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