Benedict solution

Benedict's Solution is a chemical reagent named after the American chemist Stanley Rossiter Benedict. It is primarily used in the detection of reducing sugars, such as fructose, lactose, and glucose.

Composition

Benedict's Solution is an aqueous solution that contains copper(II) sulfate, sodium carbonate, and sodium citrate. The copper(II) sulfate acts as a source of Cu2+ ions, while the sodium carbonate provides a basic environment for the reaction. Sodium citrate acts as a complexing agent, preventing the precipitation of copper(II) hydroxide.

Use

The primary use of Benedict's Solution is in the detection of reducing sugars. When heated with a reducing sugar, the solution undergoes a color change from blue to green, yellow, orange, or red, depending on the amount of sugar present. This color change is due to the reduction of copper(II) ions to copper(I) ions, which form a red precipitate of copper(I) oxide.

Preparation

To prepare Benedict's Solution, one part of copper(II) sulfate is dissolved in an aqueous solution of two parts sodium carbonate and twelve parts sodium citrate. The solution is then diluted with water to the desired concentration.

Limitations

While Benedict's Solution is a useful tool in the detection of reducing sugars, it does have some limitations. It cannot detect non-reducing sugars, such as sucrose, unless they are first broken down into reducing sugars. Additionally, the test is not quantitative; the color change can indicate the presence and relative amount of reducing sugar, but it cannot provide an exact concentration.

See Also

• Fehling's solution
• Tollens' reagent
• Reducing sugar