Salting out - Enseki

[ I ] The phenomenon in which dispersoids precipitate when a large amount of electrolyte is added to a lyophilic sol. Once precipitated, dispersoids reversibly return to the original sol when the electrolyte is removed. Ammonium sulfate and magnesium sulfate are often used as electrolytes. This is used in the separation and purification of proteins and in the manufacture of soap. [ II ] The phenomenon in which the extraction rate of the target substance increases by adding inorganic salts to the extraction system during solvent extraction. This phenomenon is mainly seen in ion-pair extraction systems. For example, when uranyl nitrate is extracted with ether, the distribution ratio of uranium increases with the addition of nitrates such as calcium nitrate or ammonium nitrate. As in this example, in addition to increasing the concentration of complex-forming ions, the addition of a salting agent reduces the activity of water in the aqueous phase or changes the activity of dissolved chemical species, increasing the distribution ratio of the target substance. For this purpose, salts that are easily hydrated, such as aluminum(III) and lithium(I), are often used.

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

【Ⅰ】親液ゾルに大量の電解質を添加したとき，分散質が沈殿する現象．いったん沈殿した分散質は，電解質を除去すれば可逆的にもとのゾルに戻る．電解質には硫酸アンモニウム，硫酸マグネシウムなどがしばしば用いられる．タンパク質の分離精製，せっけんの製造などに利用される．【Ⅱ】溶媒抽出において抽出系に無機塩類を添加することにより目的物の抽出率が増加する現象をいう．主としてイオン対抽出系に見られる現象であるが，たとえば硝酸ウラニルのエーテル抽出に際して，硝酸カルシウム，硝酸アンモニウムなど硝酸塩の添加とともにウランの分配比が大きくなる現象が知られている．この例のように，錯形成イオンの濃度を増大する効果のほかに，塩析剤の添加は水相中の水の活量の減少，あるいは溶存化学種の活量に変化をもたらし，目的物の分配比を増加させる．このような目的には水和しやすいアルミニウム(Ⅲ)やリチウム(Ⅰ)などの塩が用いられることが多い．

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