Bial's Test for Pentoses 2.0

Bial's Test is used to identify a Pentose. 2 mL of Bial's Reagent (Orcinol, Hydrochloric acid & Ferric chloride) was added to 0.5 mL of each sample. Samples were then heated for 3 min in boiling water, followed by cooling in an ice water bath. Pentoses will be dehydrated furfural in the reaction, which will react with the Orcinol to produce a blue-green colour change. Hexoses will be dehyrdated to hydromethylfurfural, which will react with the Orcinol to produce a muddy brown colour change. Take note that if polysaccharides and disaccharides are heated too long, the glycosidic bond may be broken, resulting in the production of monosaccharides. This will result in a positive Bial's test. Heating was repeated and reduced to 1 min in an attempt to only see a reaction from monosaccharides. Blue colour change = Pentose Muddy Brown colour change = Hexose Negative Control = Distilled Water Pentose Positive Control = 1 % (w/v) Xylose Hexose Positive Control = 1 % (w/v) Glucose Unknowns Tested = 13 Alphabetical list of Samples all 1% (w/v) or (v/v): Acetic Acid, Albumin, Arabinose, Fructose, Galactose, Glucose, Glycerol, Glycogen, Lactose, Maltose, Starch, Sucrose, Xylose