Fehling's A is a chemical solution used in the Fehling's test, which helps identify reducing sugars. It is a blue solution containing copper(II) sulfate, which reacts with sugars to form a red precipitate of copper(I) oxide when heated. This reaction indicates the presence of reducing sugars, such as glucose and fructose. Fehling's A is typically used in conjunction with Fehling's B, which contains sodium potassium tartrate and sodium hydroxide. Together, these solutions create an alkaline environment necessary for the reaction to occur. The test is commonly used in laboratories for sugar analysis in various samples.