Difference between revisions of "Benedict's reagent"
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==Reagent== | ==Reagent== | ||
| − | The reagent is prepared by dissolving 100 g of anhydrous [[sodium carbonate]], 173 g of [[trisodium citrate]] dihydrate and 17.3 g of [[copper(II) sulfate]] pentahydrate in water, and diluting to 1 litre.<ref name="Benedict"/> The final solution is 71.3 | + | The reagent is prepared by dissolving 100 g of anhydrous [[sodium carbonate]], 173 g of [[trisodium citrate]] dihydrate and 17.3 g of [[copper(II) sulfate]] pentahydrate in water, and diluting to 1 litre.<ref name="Benedict"/> The final solution is {{nowrap|71.3 mmol dm<sup>−3</sup>}} in copper(II) and {{nowrap|588 mmol dm<sup>−3</sup>}} in total citrate (an eightfold excess over copper), with a [[pH]] of about 12. The copper(II) is believed to be present as a 1:1 citrate [[complex]], {{nowrap|[Cu(C<sub>6</sub>H<sub>5</sub>O<sub>7</sub>)(OH)(H<sub>2</sub>O)<sub>''n''</sub>]<sup>2−</sup>}} (''n'' = 0, 1).<ref>{{citation | first1 = Terrence B. | last1 = Field | first2 = Janet L. | last2 = McCourt | first3 = W. A. E. McBryde | title = Composition and Stability of Iron and Copper Citrate Complexes in Aqueous Solution | url = http://article.pubs.nrc-cnrc.gc.ca/ppv/RPViewDoc?issn=1480-3291&volume=52&issue=17&startPage=3119 | journal = Can. J. Chem. | year = 1974 | volume = 52 | pages = 3119–24}}.</ref> The prepared solution can be stored for at least a year under normal laboratory conditions, unlike [[Fehling's solution]] or [[Tollen's reagent]], which must be prepared freshly before each use.<ref name="Benedict"/> |
==References== | ==References== | ||
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{{wikipedia|Benedict's reagent}} | {{wikipedia|Benedict's reagent}} | ||
*[http://jchemed.chem.wisc.edu/JCESoft/CCA/CCA5/MAIN/1ORGANIC/ORG18/TRAM18/B/MENU.HTM Benedict's Test for Reducing Sugars] | *[http://jchemed.chem.wisc.edu/JCESoft/CCA/CCA5/MAIN/1ORGANIC/ORG18/TRAM18/B/MENU.HTM Benedict's Test for Reducing Sugars] | ||
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| + | [[Category:Reagents for qualitative analysis]] | ||
{{CC-BY-3.0}} | {{CC-BY-3.0}} | ||
Revision as of 11:24, 7 April 2010
Benedict's reagent, also called Benedict's solution, is a reagent used to test for reducing sugars, named after American chemist Stanley Rossiter Benedict.[1][2] Similar to Fehling's solution, it is an alkaline solution of copper(II), but it is stabilized by citrate ions rather than tartrate ions and is less corrosive and more stable to storage.[2]
Reagent
The reagent is prepared by dissolving 100 g of anhydrous sodium carbonate, 173 g of trisodium citrate dihydrate and 17.3 g of copper(II) sulfate pentahydrate in water, and diluting to 1 litre.[1] The final solution is 71.3 mmol dm−3 in copper(II) and 588 mmol dm−3 in total citrate (an eightfold excess over copper), with a pH of about 12. The copper(II) is believed to be present as a 1:1 citrate complex, [Cu(C6H5O7)(OH)(H2O)n]2− (n = 0, 1).[3] The prepared solution can be stored for at least a year under normal laboratory conditions, unlike Fehling's solution or Tollen's reagent, which must be prepared freshly before each use.[1]
References
- ↑ 1.0 1.1 1.2 Benedict, Stanley R. A Reagent For the Detection of Reducing Sugars. J. Biol. Chem. 1908, 5 (6), 485–87, <http://www.jbc.org/content/5/5/485.full.pdf>.
- ↑ 2.0 2.1 Simoni, Robert D.; Hill, Robert L.; Vaughan, Martha Benedict's Solution, a Reagent for Measuring Reducing Sugars: the Clinical Chemistry of Stanley R. Benedict. J. Biol. Chem. 2002, 277 (16), e5, <http://www.jbc.org/content/277/16/e5.full.pdf>.
- ↑ Field, Terrence B.; McCourt, Janet L. Composition and Stability of Iron and Copper Citrate Complexes in Aqueous Solution. Can. J. Chem. 1974, 52, 3119–24, <http://article.pubs.nrc-cnrc.gc.ca/ppv/RPViewDoc?issn=1480-3291&volume=52&issue=17&startPage=3119>.
External links
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See also the corresponding article on Wikipedia. |
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