Fehling's test involves the use of Fehling's solution, which consists of two separate solutions: Fehling's A (copper(II) sulfate) and Fehling's B (potassium sodium tartrate in a strong alkali, usually sodium hydroxide). When these two solutions are mixed, they form a deep blue solution due to the formation of a complex between the copper ions and the tartrate ions. This solution is then used to test for the presence of reducing sugars.
