Reflux to apply energy to chemical reactions

Laboratory reflux apparatus for adding energy to a chemical reaction

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 purpose is to thermally accelerate the reaction by conducting it at an elevated temperature (i.e. the solvent's boiling point.) Liebig condenser The Liebig condenser or straight condenser is a piece of laboratory equipment consisting of a straight glass tube surrounded by a water jacket. ... For other uses, see Solvent (disambiguation). ... Italic text This article is about the boiling point of liquids. ...

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, one can be sure that the reaction will proceed at a constant temperature. By careful choice of solvent, one can control the temperature within a very narrow range. The constant boiling action also serves to continuously mix the solution, although a magnetic stirring rod mechanism is often used to achieve a uniform solution. This technique is useful for performing chemical reactions under controlled conditions that require substantial time for completion. In the physical sciences, a phase is a set of states of a macroscopic physical system that have relatively uniform chemical composition and physical properties (i. ... Making a saline water solution by dissolving table salt (NaCl) in water This article is about chemical solutions. ...

The diagram shows a typical reflux apparatus for applying energy to chemical reactions. It 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. In modern laboratories, open flames are avoided due to the many flammable solvents often in use, and electrical heating, (i.e., with a hot plate or mantle) is preferred. Furthermore, a high boiling, thermally stable silicone oil is generally used to immerse the reaction vessel, rather than water which evaporates too readily to be useful for lengthy reactions. Using an oil bath, temperatures of up to several hundred degrees can easily be achieved, which is higher than the boiling point of most commonly used solvents. If even higher temperatures are required, the oil bath can be replaced with a sand bath. Look up Bunsen burner in Wiktionary, the free dictionary. ... A hot plate is a small electric stove often used in a laboratory setting to heat glassware. ... Silicone oils (polymerized siloxanes) are silicon analogues of carbon based organic compounds, and can form (relatively) long and complex molecules based on silicon rather than carbon. ... For other uses, see Solvent (disambiguation). ... A sand bath is a common piece of laboratory equipment made from a container filled with heated sand. ...

Reflux in beverage distillation

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, a process of multiple distillations or charcoal filtering may be applied to obtain a product lacking in any suggestion of its original source material for fermentation. The molecular mass of a substance (less accurately called molecular weight and abbreviated as MW) is the mass of one molecule of that substance, relative to the unified atomic mass unit u (equal to 1/12 the mass of one atom of carbon-12). ... This article does not cite any references or sources. ... Fusel alcohols, also sometimes called fusel oils, are higher order (more than two carbons) alcohols formed by fermentation and present in cider, mead, beer, wine, and spirits to varying degrees. ... For other uses, see Applejack. ... Vodka bottling machine, Shatskaya Vodka Shatsk, Russia Vodka (Polish: wódka, Russian: водка) is one of the worlds most popular distilled beverages. ... For other uses, see Fermentation. ...

See also

• Batch distillation
• Fractional distillation
• Fractionating column

References

1. ^ Kister, Henry Z. (1992). Distillation Design, 1st Edition, McGraw-Hill. 0070349096. 
2. ^ Perry, Robert H. and Green, Don W. (1984). Perry's Chemical Engineers' Handbook, 6th Edition, McGraw-Hill. 0070494797. 

External links

• Distillation column components

Gallery

Toluene is refluxed with sodium-benzophenone desiccant before it is distilled to give pure oxygen- and water-free toluene. Bold textBold textBatch distillation[1] refers to the use of distillation, the separation of components in a system by volatilities, in batches. ... Fractional distillation is the separation of a mixture into its component parts, or fractions, such as in separating chemical compounds by their boiling point by heating them to a temperature at which several fractions of the compound will evaporate. ... A fractionating column is an essential item used in the distillation of liquid mixtures so as to separate the mixture into its component parts, or fractions, based on the differences in their volatilities. ... Distillation Design provides complete coverage of the design of industrial distillation columns for the petroleum refining, chemical and petrochemical plants, natural gas processing, pharmaceutical, food and alcohol distilling industries. ... Perrys Chemical Engineers Handbook was first published in 1934 and the seventh edition was published in 1997. ... Image File history File linksMetadata Download high-resolution version (1200x1600, 387 KB) Toluene is refluxed in sodium-benzophenone to remove oxygen and water, before being distilled. ... Toluene, also known as methylbenzene or phenylmethane is a clear, water-insoluble liquid with the typical smell of paint thinners, redolent of the sweet smell of the related compound benzene. ... For sodium in the diet, see Salt. ... Benzophenone, also known as diphenylmethanone, phenyl ketone, diphenyl ketone, or benzoylbenzene. ... A dessicant is a hygroscopic substance that induces or sustains a state of dryness (desiccation) in its local vicinity in a moderately-well sealed container. ...

Industrial fractionating columns all of which use reflux Image File history File linksMetadata Download high-resolution version (1609x2120, 552 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Distillation Fractional distillation Fractionating column User talk:Shanel Reflux Continuous distillation User talk:Randfan/Super Desk Metadata This...

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