The technique of foam fractionation for the separation of substances has been known for a long time (4). Foam separation takes advantage of the surface activity of certain solutes at a gas liquid interface. When a solution is foamed, the active components collect at the surface or foam layer, which can then be removed and broken to give a rich liquid product. An excellent review of the whole field can be found in an article by Rubin and Gaden (7).Initially, only surface active substances which formed stable foams were separated by foam fractionation, and the applications were therefore somewhat limited. More recently it has been found that even nonsurfaceactive compounds can be separated by this technique. For example, metal ions have been separated by adding to the solution a foaming agent which can complex the metal ions and carry them into the foam (8). Karger and Rogers (8) have separated organic compounds which do not form stable foams by themselves. They showed
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