Seliwanoff's Test

Seliwanoff'sTest

Purpose: 

         Seliwanoff'sTest is performed to distinguish between ketose sugar and aldose sugar.

 Composition of the Reagent:

         0.1 gm resorcinol in 100 ml of 0.5 N HCl i.e., 50%(v/v) HCl.

  Principles:

(i) In Conc. HCl , ketoses dehydrated and produce hydroxymethylfurfural rapidly.

(ii) This furfural derivative reacts with the resorcinol and produced deep-red /cherry red ketooses (of fructose).

Experiment	Observation	Inference
1 ml sample solution + 3 ml Seliwanoff's reagent. The mixture is heated over the flame for 30 seconds.	The mixture solution turns cherry red rapidly.	Ketoses (of fructose) present in the sample solution.

 

Note: 

Hydrolysed sucrose also responses in this test as fructose is one of the product of the hydrolysed sucrose.

Reactions:-

1. D-glucose of the sample + HCl (H+) --->Hydroxymethylfurfural + 3 H²O

2. Hydroxymethylfurfural + 2 resorcinol + HCl (H+) —-> Cherry red compound( of ketoses) + 3 H²O