An Easlly Assembled, Convertible Liquid/Liquid Continuous Extractor Continuous extraction of water-soluble organic compounds from an aqueous solution to an organic solvent is one of the common techniques for advanced organic chemistry.' However, the continuous extractor is not standard glassware, which limits its use in undergraduate laboratory teaching. We wish to describe here a continuous extractor that can be easily assembled from some common laboratory glassware. As illustrated in the figure, the main apparatus to be used is a pressure-equalized addition funnel. This setup is suitable for extracting organic compounds from an aqueous solution by an organic solvent either lighter or denser than water. For extraction using a solvent heavier than water, glass tube C can he taken out of the device. To start the extraction, a sufficient amount of organic solvent is added to the aqueous solution inside the addition funnel. The level of the aqueous layer should he kept lower than the sidearm of the funnel. Enough organic solvent is placed in the round-bottomed flask and is refluxed with a heating device. The solvent is evaporated through the sidearm of the addition funnel and condensed hack into the funnel. Stopcock B is adjusted in such a manner that the dropping Brate is similar to the condensation rate of the organic solvent. When the solvent is condensed, it will pass through the aqueous layer and the organic substances that are being extracted. As the operation continues, the organic substances will be successively extracted into flask A. For extraction using solvent lighter than water, stopcock B is closed and a specially made glass tube C is inserted into the funnel. The receiving end of tube C is enlarged as shown so that most of the condensing liquid can be collected and directed to the bottom of the addition funnel. In an extraction operation, the organic solvent in flask A is heated and evaporated through the sidearm of the funnel to condenser D. Upon cooling, the major portion of the condensate drips into and through tube C to the bottom of the funnel. The condensing liquid after coming in contact with the aqueous layer will eventually rise to the top and push the organic solution to the solvent reservoir A through the sidearm. By this operation, the continuous extraction nrocess can he efficientlv effected. BYadjusting the sin; of the addition funnel, a different scale of extraction can be achieved. We have used both diethyl ether and dichhmmethane to extract organic substances continuously from water with this de\,ice.
Vogel, A. I. A Tertbook of~ractiealO~ganicChemistry, 3rd ed.; Longmans: London, 1956; p 152.
Wlng Hong Chan and Wal Keung Yu Hong Kong Baptist College 224. Waterlw Road. Kawlwn. Hang Kong
634
Journal of Chemical Education
