1. Quantitative Estimation of Pentose
When pentoses are heated with conc. HCl , furfural is formed which condenses with orcinol in the presence of ferric ions to give a blue-green color.

2. * Principle ∆ +
HCl
Furfural
Pentose

3. * Principle
Fe+3 +
Blue Green
Complex
Furfural
Orcinol

4. Materials 1. Orcinol reagent (0.2% in conc. H2SO4 ).
2. Ribose 2mg/ml (0.2%) in water.
3. Colorimeter or spectrophotometer.

5. Boiling Water Bath Mix Well Read the Optical Density at 665 nm
Tube # Blank St unk.
25 min. 60 30 15 45 5 10 20 25 35 40 50 55
Boiling Water Bath
Orcinol (ml)
Pentose (ml)
D.W (ml)
Mix Well
COOL to Room Temperature in cold water
Read the Optical Density at 665 nm

6. * Calculations CUn. = A Un. × C St.
Absorbance of Unknown Absorbance of Standard =
Concentration of Unknown Concentration of Standard
CUn. = A Un. × C St.
A St.
Samar A. Damiati