Nylander’s Test is a type of chemical test used to determine the presence of reducing sugars. Sugars like fructose and glucose can reduce bismuth oxynitrate down to bismuth when under alkaline conditions. If Nylander’s test reagent which is comprised of bismuth Nitrate along with potassium sodium tartrate as well as potassium hydroxide mixed into a solution containing reduction sugars, a dark bismuth precipitate has created.
Reducing sugar is a kind of sugar which acts like a reduction agent. It is able to efficiently transfer electrons to another molecule through oxidising it. In another sense the term “reducing sugar” refers to any sugar that is likely to function as a reduction agent since it has either the aldehyde group (-CHO) or an keto group. (-CO-). The purpose of the Nylander test is to detect the presence of sugars with reducing properties. Under alkaline conditions glucose or fructose transforms bismuth oxynitrate into bismuth.
Principle of Nylander’s Test
Aldehyde group or free ketone of carbohydrate reduces and forms black precipitates bismuth subnitrate reduced to black bismuth. A very tiny amounts of glucose (0.08 percent) can be identified through this test.
- Materials: Test tube, Test tube stand, Water Bath, Weighing balance
- Chemicals: Bismuth Subnitrate, Glucose or Fructose, Potassium Hydroxide, Rochelle salt
- Reagent: Nylander’s Reagent (Dissolve 4 grams in Rochelle salt with 2 grams of bismuth in 10 percent solution (100mL) of potassium hydroxide..)
Procedure of Nylander’s Test
- Place 5ml of sample (Glucose or fructose) solution into the test tube.
- Add about 5-8 drops of Nylander’s reagent.
- Boil the test tube for 3 minutes in the water bath, then allow to cool at the room temperature.
Nylander’s Test Result
The black precipitates form within a short time (bismuth subnitrate is reduced to bismuth black), indicates the positive test.