Illustrated Glossary of Organic Chemistry

Benedict's test: A chemical reaction used to test for the presence of an aldehyde in an unknown, frequently a carbohydrate. To perform the test, one adds Benedict's solution (a blue solution containing Cu2+) to the material to be tested. If an aldehyde is present, a brick red Cu2O precipitate is formed.

Add glucose

Benedict's solution is blue (due to
Cu2+) before addition of the unknown.
A positive Benedict's test is indicated
by a yellowish to red precipitate of Cu2O.