Difference between revisions of "Fehling's reagent"
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==Reagent== | ==Reagent== | ||
| − | The reagent is prepared immediately before use by mixing equal | + | The reagent is prepared immediately before use by mixing equal volumes of two solutions: |
;Solution A: 70 g of [[copper(II) sulfate]] pentahydrate dissolved in water and diluted to one litre | ;Solution A: 70 g of [[copper(II) sulfate]] pentahydrate dissolved in water and diluted to one litre | ||
;Solution B: 350 g of [[potassium sodium tartrate]] tetrahydrate ("Rochelle salt") and 100 g of sodium hydroxide dissolved in water and diluted to one litre | ;Solution B: 350 g of [[potassium sodium tartrate]] tetrahydrate ("Rochelle salt") and 100 g of sodium hydroxide dissolved in water and diluted to one litre | ||
| + | The final reagent is {{nowrap|140 mmol dm<sup>−3</sup>}} in copper(II) and {{nowrap|620 mmol dm<sup>−3</sup>}} in total tartrate (a fourfold excess over copper), with a [[pH]] of about 14. The copper(II) is present as a variety of tartrate [[complex]]es, [Cu(C<sub>4</sub>H<sub>4</sub>O<sub>6</sub>)<sub>''n''</sub>]<sup>(2''n''−2)−</sup> (''n'' = 2–6),<ref>{{citation | title = Novel Copper-Tartrate Coordination Compounds | first = Neil D. | last = Jespersen | doi = 10.1080/00032717208064332 | journal = Anal. Lett. | volume = 5 | issue = 7 | year = 1972 | pages = 497–508}}.</ref> which prevents the precipitation of [[copper(II) hydroxide]] or sparingly soluble [[copper(II) tartrate]].<ref>{{citation | title = Synthesis and crystal structure of a novel tartrate copper(II) two-dimensional coordination polymer: {[Cu2(C4H4O6)2(H2O)2]·4H2O}infin | last1 = Jian | first1 = Fangfang | last2 = Zhao | first2 = Pusu | last3 = Wang | first3 = Qingxiang | journal = J. Coord. Chem. | volume = 58 | issue = 13 | year = 2005 | pages = 1133–38 | doi = 10.1080/00958970500148446}}.</ref> | ||
==References== | ==References== | ||
Revision as of 13:36, 7 April 2010
Fehling's reagent, also called Fehling's solution, is a reagent used to test for reducing sugars, named after German chemist Hermann von Fehling. It is an alkaline solution of copper(II) stabilized by tartrate ions.
Reagent
The reagent is prepared immediately before use by mixing equal volumes of two solutions:
- Solution A
- 70 g of copper(II) sulfate pentahydrate dissolved in water and diluted to one litre
- Solution B
- 350 g of potassium sodium tartrate tetrahydrate ("Rochelle salt") and 100 g of sodium hydroxide dissolved in water and diluted to one litre
The final reagent is 140 mmol dm−3 in copper(II) and 620 mmol dm−3 in total tartrate (a fourfold excess over copper), with a pH of about 14. The copper(II) is present as a variety of tartrate complexes, [Cu(C4H4O6)n](2n−2)− (n = 2–6),[1] which prevents the precipitation of copper(II) hydroxide or sparingly soluble copper(II) tartrate.[2]
References
- ↑ Jespersen, Neil D. Novel Copper-Tartrate Coordination Compounds. Anal. Lett. 1972, 5 (7), 497–508. DOI: 10.1080/00032717208064332.
- ↑ Jian, Fangfang; Zhao, Pusu; Wang, Qingxiang Synthesis and crystal structure of a novel tartrate copper(II) two-dimensional coordination polymer: {[Cu2(C4H4O6)2(H2O)2·4H2O}infin]. J. Coord. Chem. 2005, 58 (13), 1133–38. DOI: 10.1080/00958970500148446.
External links
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See also the corresponding article on Wikipedia. |
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