Bial's Test

Bial's Test:

The test reagent dehydrates pentoses to form furfural.

Bial’s reagent:

Bial’s reagent contain a solution of orcinol, HCl and ferric chloride which is very corrosive, so it was handled very carefully.

How to perform the test:

Two cm3 of Bial’s reagent are placed in a test tube for each reaction to be tested. Four drops of each carbohydrate solution were placed in each tube, and heated for one minute in a boiling water bath. The test tubes are examined for a blue-green color indicating the presence of pentose sugars.
If the color is not obvious, more water can be added to the tube.


Reactions:

Furfural further reacts with orcinol and
the iron ion present in the test reagent to produce a bluish product .

Physical propertice:

The formation of a bluish product. All other colors indicate a negative result for pentoses.
Note that hexoses generally react to form green, red, or brown products.