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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Fehling's solution is the name given to a chemical reagent, primarily used to differentiate between water-soluble carbohydrate and ketone functional groups. It can also be used as a test for reducing sugars and non reducing sugars. This reagent is prepared from two solutions, a basic solution of potassium sodium tartrate and a solution of copper(II) sulfate.
Reagent "A" and Reagent "B" are available from Sigma Aldrich.
- Fehling's "A" uses 7 g CuSO4·5H2O dissolved in distilled water containing 2 drops of dilute sulfuric acid.
- Fehling's "B" uses 35g of potassium tartrate and 12g of NaOH in 100 ml of distilled water.
These two solutions should be stoppered and stored until needed.
For the test: Mix 15 ml of solution-"A" with 15 ml of solution-"B" Add 2 ml of this mixture to an empty test tube. Add 3 drops of the compound to be tested to the tube. Place the tube in a water-bath at 60° C.
A positive test is indicated by a green suspension and a red precipitate
Solution A and B should be stored separately in tightly stoppered bottles. They are stable under normal temperatures and pressures.
Preparation from UWI at Mona, Jamaica: []