A Simple Liquid-Liquid Continuous Extractor When the distribution coefficient of a desired compound between two solvents is small, continuous extraction may he utilized to transfer most of the material to the solvent in which it is less soluhle. Commercially available apparatus to carry this out is expensive and often limited to one size flask. For extractions of a material from a more-dense to a less-dense solvent, the set-up depicted is convenient and can he constructed entirely from readily available glassware of size appropriate to the volumes required. Flask A contains the more-dense solvent/solute solution and flask B the less-dense solvent, which is boiled hv use of a heating mantle (not shown). Adapter C is of the standard vacuum variety, and has thekacuum take-offbealed, either temporarilyor permanently. Glass tuhe D is hung from a thin wire W so that its widened ton catches most of the solvent from condenser F,which is water-cooled. Condenser E is not cooled, and serves to extend the height of the apparatus so that the less-dense solvent can form a column in tuhe D sufficient to extrude into the denser solvent in flask A. There it is caught by the magnetic stirrer G and broken into tiny drops to increase the efficiency of the extraction. The less-dense solvent dissolves some solute, rises to the top of flask A, returns to flask B, where the distillatian-condensationcycle is repeated, causing the desired solute to accumulate gradually in flask B. If the joints are very lightly lubricated with silicon grease, such a set-up can he used, for example, t o extract an aqueous solution with petroleum ether for periods of s week or more without noticeable leakage. Vassar Callege Poughkeepsie, New York 12601
Richard W. Holder
Volume 50, Number 9, September 1973 / 639
