Benedict's reagent

Contains Cu2+ ions in alkaline solution with sodium citrate added to keep the cupric ions in solution. The alkaline conditions of this test causes isomeric transformation of ketoses to aldoses, resulting in all monosaccharides and most disaccharides reducing the blue Cu2+ ion to cuprous oxide (Cu2O), a brick red-orange precipitate. This solution has been used in clinical laboratories for testing
urine.