Question #76bc1
1 Answer
How about these?
Explanation:
Starch
One way to distinguish starch is to use a cat toy — a simple laser pointer — to shine a beam of light through "solutions" of each.
Unlike the others, starch forms a colloidal dispersion, in which the starch particles are large enough to disperse the light.
Glucose
You could prepare a crystalline osazone.
Osazone crystals from different sugars have characteristic shapes.
Place 0.1 g sugar, 0.2 g phenylhydrazine hydrochloride, 0.3 g sodium acetate,
and 2 mL water in a small loosely-corked test tube and heat in boiling water.
Shake the test tube occasionally without removing it from the water.
The osazone should precipitate within about 5 min.
Observe the moist brush-shaped crystals under the microscope.
Sucrose
A simple colorimetric test for sucrose is the Seliwanoff test.
An indicator solution is prepared by dissolving 50 mg of resorcinol in 100 mL of 4 mol/L
Add about 0.5 mL of a solution of the unknown carbohydrate to a test tube containing 3 mL of the freshly prepared indicator and heat the mixture to boiling.
A cherry red color develops within about 5 min if sucrose is present.
