
n.
An aqueous solution of copper sulfate, sodium hydroxide, and potassium sodium tartrate used to test for the presence of sugars and aldehydes in a substance, such as urine.
[After Hermann von Fehling (1812-1885), German chemist.]
On this page
American Heritage Dictionary:
Feh·ling's solution |

[After Hermann von Fehling (1812-1885), German chemist.]
|
Featured Videos:
|
Columbia Encyclopedia:
Fehling's solution |
Oxford Dictionary of Biochemistry:
Fehling's solution |
| Federation of European Biochemical Societies, FeMo-co, FeMo protein | |
| Fenton reaction, Fernández-Morán particle, Feulgen reaction |
Saunders Veterinary Dictionary:
Fehling's solution |
A solution used in clinical pathology as a test for glucose in solutions such as urine. (1) 34.66 g cupric sulfate in water to make 500 ml; (2) 173 g crystallized potassium and sodium tartrate and 50 g sodium hydroxide in water to make 500 ml; mix equal volumes of (1) and (2) at time of use.
Wikipedia on Answers.com:
Fehling's solution |
Fehling's solution is a chemical test used to differentiate between water-soluble aldehyde and ketone functional groups, and as a test for monosaccharides. The test was developed by German chemist Hermann von Fehling in 1849.[1]
|
Contents
|
Fehling's solution is always prepared fresh in the laboratory. It is made initially as two separate solutions, known as Fehling's A and Fehling's B. Fehling's A is a blue aqueous solution of copper(II) sulfate, while Fehling's B is a clear solution of aqueous potassium sodium tartrate (also known as Rochelle salt) and a strong alkali (commonly sodium hydroxide).
Equal volumes of the two mixtures are mixed together to get the final Fehling's solution, which is a deep blue colour. In this final mixture, aqueous tartrate ions from the dissolved Rochelle salt chelate to Cu2+ (aq) ions from the dissolved copper(II) sulfate, as bidentate ligands giving the bistartratocuprate(II)4- complex as shown below. The tartarate ions, by complexing copper prevent the formation of Cu(OH)2 from the reaction of CuSO4.2H2O and NaOH present in the solution.
Fehling's can be used to determine whether a carbonyl-containing compound is an aldehyde or a ketone. The bistartratocuprate(II) complex in Fehling's solution is an oxidizing agent and the active reagent in the test. The compound to be tested is added to the Fehling's solution and the mixture is heated. Aldehydes are oxidized, giving a positive result, but ketones do not react, unless they are alpha-hydroxy-ketones. The bistartratocuprate(II) complex oxidizes the aldehyde to a carboxylate anion, and in the process the copper(II) ions of the complex are reduced to copper(I) ions. Red copper(I) oxide then precipitates out of the reaction mixture, which indicates a positive result i.e. that redox has taken place (this is the same positive result as with Benedict's solution. A negative result is the absence of the red precipitate; it is important to note that Fehling's will not work with aromatic aldehydes; in this case Tollens' reagent should be used.
Fehling's test can be used as a generic test for monosaccharides. It will give a positive result for aldose monosaccharides (due to the oxidisable aldehyde group) but also for ketose monosaccharides, as they are converted to aldoses by the base in the reagent, and then give a positive result.[2] For this reason, Fehling's reagent is sometimes referred to as a general test for monosaccharides.
Fehling's can be used to screen for glucose in urine, thus detecting diabetes. Another use is in the breakdown of starch to convert it to glucose syrup and maltodextrins in order to measure the amount of reducing sugar, thus revealing the dextrose equivalent (DE) of the starch sugar.
Formic acid (HCOOH - methanoic acid) also gives a positive Fehling's test result, as it does with Tollens' test and Benedict's test also. This is because it is readily oxidizable to carbon dioxide and water.
Sodium hydroxide is corrosive at high concentrations and precautions should be taken as such not to come into direct contact with it. Copper(II) sulfate is also toxic if ingested.[2]
Crystal structure of the copper(I) oxide precipitate
This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)
| fehling | |
| indiglucin | |
| copper number (analytical chemistry) |
| What will aldehyde give with fehling solution? Read answer... | |
| What is the composition of fehling\'s solution? Read answer... | |
| What is a fehling solution a and b? Read answer... |
| How do you make fehling solution? | |
| What is the composition of fehling\'s solution and what are its functions? | |
| What will happen if Fehling Solution is boiled? |
Copyrights:
![]() |
![]() | American Heritage Dictionary. The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved. Read more |
![]() |
![]() | Columbia Encyclopedia. The Columbia Electronic Encyclopedia, Sixth Edition Copyright © 2012, Columbia University Press. Licensed from Columbia University Press. All rights reserved. www.cc.columbia.edu/cu/cup/. Read more |
| Oxford Dictionary of Biochemistry. Oxford University Press. Oxford Dictionary of Biochemistry and Molecular Biology © 1997, 2000, 2006 All rights reserved. Read more | ||
![]() | Saunders Veterinary Dictionary. Saunders Comprehensive Veterinary Dictionary 3rd Edition. Copyright © 2007 by D.C. Blood, V.P. Studdert and C.C. Gay, Elsevier. All rights reserved. Read more | |
![]() |
![]() | Wikipedia on Answers.com. This article is licensed under the Creative Commons Attribution/Share-Alike License. It uses material from the Wikipedia article Fehling's solution. Read more |
Mentioned in