Difference between revisions of "Barfoed's reagent"
Physchim62 (talk | contribs) (Created page with ''''Barfoed's reagent''' is a reagent used to test for reducing monosaccharides, named after Danish chemist Christen Barfoed.<ref>{{citation | title…') |
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==Reagent== | ==Reagent== | ||
| − | The reagent is prepared by dissolving | + | The reagent is prepared by dissolving 66 g of [[copper(II) acetate]] monohydrate and 10 cm<sup>3</sup> of glacial [[acetic acid]] in water, and diluting to 1 litre.<ref>{{RubberBible62nd|page=D-111}}.</ref> The final solution is {{nowrap|338 mmol dm<sup>−3</sup>}} in copper(II) and {{nowrap|850 mmol dm<sup>−3</sup>}} in total acetate (2½ [[equivalent]]s relative to copper), with a [[pH]] of about 3. |
==Test== | ==Test== | ||
Latest revision as of 15:20, 7 April 2010
Barfoed's reagent is a reagent used to test for reducing monosaccharides, named after Danish chemist Christen Barfoed.[1] It is a solution of copper(II) acetate in dilute acetic acid.
Contents
Reagent
The reagent is prepared by dissolving 66 g of copper(II) acetate monohydrate and 10 cm3 of glacial acetic acid in water, and diluting to 1 litre.[2] The final solution is 338 mmol dm−3 in copper(II) and 850 mmol dm−3 in total acetate (2½ equivalents relative to copper), with a pH of about 3.
Test
A few drops of the solution to be tested are added to about 5 cm3 of the reagent in a test tube. The mixture is heated to 100 °C and kept at that temperature for about five minutes, then allowed to cool. The appearance of a brick-red precipitate (copper(I) oxide) indicates the presence of a reducing monosaccharide: disaccharides do not react. Several substances interfere with the test, including high concentrations of chloride ions.[3]
References
- ↑ Barfoed, C. Ueber die Nachweisung des Traubenzuckers neben Dextrin und verwandten Körpern. Fresenius Z. Anal. Chem. 1873, 12 (1), 27–32. DOI: 10.1007/BF01462957.
- ↑ CRC Handbook of Chemistry and Physics, 62nd ed.; Weast, Robert C., Ed.; CRC Press: Boca Raton, FL, 1981; p D-111. ISBN 0-8493-0462-8.
- ↑ Welker, William H. A Disturbing Factor in Barfoed's Test. J. Am. Chem. Soc. 1915, 37 (9), 2227–30. DOI: 10.1021/ja02174a036.
External links
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See also the corresponding article on Wikipedia. |
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