Bial's test
Encyclopedia
Bial's test is a chemical test for the presence of pentose
Pentose
A pentose is a monosaccharide with five carbon atoms. Pentoses are organized into two groups. Aldopentoses have an aldehyde functional group at position 1...

s. The components include orcinol
Orcinol
Orcinol is a natural phenolic organic compound that occurs in many species of lichens including Rocella tinctoria and Lecanora. It can be formed by fusing extract of aloes with potash....

, hydrochloric acid
Hydrochloric acid
Hydrochloric acid is a solution of hydrogen chloride in water, that is a highly corrosive, strong mineral acid with many industrial uses. It is found naturally in gastric acid....

, and ferric chloride. In the presence of a pentose, the pentose will be dehydrated to form furfural
Furfural
Furfural is an organic compound derived from a variety of agricultural byproducts, including corncobs, oat, wheat bran, and sawdust. The name furfural comes from the Latin word , meaning bran, referring to its usual source....

. The solution will turn bluish and a precipitate may form. The solution shows two absorption bands, one in the red between B and C
Fraunhofer lines
In physics and optics, the Fraunhofer lines are a set of spectral lines named for the German physicist Joseph von Fraunhofer . The lines were originally observed as dark features in the optical spectrum of the Sun....

 and the other near the D line .

Composition

Bial's reagent consists of 0.4gm orcin, 200 ml of concentrated hydrochloric acid and 0.5 ml of a 10% solution of ferric chloride .
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