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Reflux

    :''This article is about reflux a technique in chemistry For information on the reflux of acid from the stomach see articles on heartburn acid indigestion and gastroesophageal reflux''
    apparatus
    Reflux is a technique used in chemistry to apply energy to reactions over an extended period of time
    A liquid reaction mixture is placed in a vessel open only at the top This vessel is connected to a Liebig condenser such that any vapours given off are cooled back to liquid and fall back into the reaction vessel The vessel is then heated vigorously for the course of the reaction
    The advantage of this technique is that it can be left for a long period of time without the need to add more solvent or fear of the reaction vessel boiling dry as any vapour is immediately condensed in the condenser In addition as a given solvent will always boil at a certain temperature you can be sure that the reaction will proceed at the same temperature; by careful choice of solvent you can even control what that temperature is
    The diagram also includes an optional beaker of water between the reactants and the heat This is often used as a safety precaution when using flammable reactants and a Bunsen burner in order to keep the flame away from the reactants

    Use in multiple stage distilation

    By controlling the temperature of the condenser a reflux still may be used to ensure that higher boiling point components (which are also of higher molecular weight are returned to the flask while lighter elements are passed out to a secondary condenser This is useful in producing high quality alcoholic beverages while ensuring that less desirable components (such as fusel alcohols) are returned to the primary flask This is particularly effective in the production of alcoholic beverages in which it is appropriate to retain the flavors and aromas of the source fruit - such as applejack For high quality neutral spirits (such as vodka) or post distillation flavored spirits (such as gin) a process of multiple distillations and/or charcoal filtering may be applied to obtain a product lacking in any suggestion of its original source for fermentation

    see also