Bial's Test for Pentoses

This test is specific to pentoses and to pentose-containing compounds and is therefore useful for pentose sugar determination. The reaction is due to the formation of furfural in the acid medium which in the presence of ferric ions, condenses with orcinol to give a blue-green complex.

Bial's test result

Bial's reagent

Dissolve 1.5g of orcinol in 100 mL of Conc HCL and add 20 drops of 10% solution of Ferric Chloride. Make yourself fresh.

Procedure

• Add 4 to 5 drops of the test solution to about 2 mL of Bial's reagent. 
• Heat until bubbles of gas rise to the surface in a boiling water bath.
• The presence of pentose sugar indicates the formation of the blue-green solution and the precipitate.

Note:

Bial's test is a chemical test used to detect the presence of pentoses, a type of monosaccharide sugar that contains five carbon atoms, in a given sample. This test is named after the German physician Manfred Bial, who developed the method in the early 1900s.

Bial's test is widely used in various fields, including biochemistry, food science, and agriculture, to determine the presence and concentration of pentoses in a given sample.