Editing Fehling's solution (section)

==Use of the reagent==
Fehling's solution can be used to distinguish [[aldehyde]] vs [[ketone]] functional groups.  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 α-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 reagent|Benedict's solution]]).

Fehling's test can be used as a generic test for [[monosaccharides]] and other reducing sugars (e.g., maltose). 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.<ref name="regensburg">{{Cite web |url=http://www.uni-regensburg.de/Fakultaeten/nat_Fak_IV/Organische_Chemie/Didaktik/Keusch/D-Fehling-e.htm |title=Fehling's Test for Reducing Sugars<!-- Bot generated title --> |access-date=2008-01-19 |archive-date=2008-01-24 |archive-url=https://web.archive.org/web/20080124171744/http://www.uni-regensburg.de/Fakultaeten/nat_Fak_IV/Organische_Chemie/Didaktik/Keusch/D-Fehling-e.htm |url-status=dead }}</ref>

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 [[maltodextrin]]s in order to measure the amount of [[reducing sugar]], thus revealing the [[dextrose equivalent]] (DE) of the [[glucose syrup|starch sugar]].

[[Formic acid]] (HCO<sub>2</sub>H) also gives a positive Fehling's test result, as it does with [[Tollens' reagent|Tollens']] (eponymous for [[Bernhard Tollens|Bernhard Christian Gottfried Tollens]] (1841 – 1918)) test and Benedict's solution also. The positive tests are consistent with it being readily oxidizable to [[carbon dioxide]].

The solution cannot differentiate between benzaldehyde and acetone.