Benedictís Solution

Introduction:

Benedict's solution is a deep-blue alkaline solution used to test for the presence of the aldehyde functional group, -CHO. The substance to be tested is heated with Benedict's solution; formation of a brick-red precipitate indicates presence of the aldehyde group. Since simple sugars (e.g., glucose) give a positive test, the solution is used to test for the presence of glucose in urine, a symptom of diabetes. One liter of Benedict's solution contains 173 grams sodium citrate, 100 grams sodium carbonate, and 17.3 grams cupric sulfate pentahydrate. When heated with reducing sugar, the cupric ion (complexed with citrate ions) is reduced to cuprous ion by the aldehyde group (which is oxidized), and precipitates as cuprous oxide, Cu2O.

 

One-liter material set:

The one-liter material set contains 3 parts in three different plastic bags as follows.

Part 1: 17.3 grams cupric sulfate pentahydrate

Part 2: 173 grams sodium citrate

Part 3: 100 grams sodium carbonate

How to prepare the solution?

1. Use a 2-liter beaker or any other large, graduated container to prepare your solution.

2. Dissolve the part 1 (Copper Sulfate, Blue Crystals) in 300 ml hot water. Stir the mixture until the copper sulfate is fully dissolved.

3. Add more hot water to bring the total volume of the solution to about 600 ml. This will help any remaining copper sulfate to dissolve and will prepare the solution for adding part 2.

4. Add part 2 (Sodium Citrate) while stirring the solution. Continue stirring until fully dissolved.

5. Add more hot water to bring the total solution up to 900 ml. This will help dissolving any remaining crystals and prepare the solution for adding part 3.

6. Add part 3 (Sodium carbonate) very slowly while stirring the solution. Continue stirring until you get the clear dark blue solution. Add more water to bring the solution up to exactly one liter.

Hazards:

This set contain hazardous materials. Keep them away from small children. Avoid skin contact and contact a physician if accidentally ingested.