A database about Preparation of Laboratory Reagents. A Project of SCIENCE Pakistan

Benedict's Reagent

Dissolve 100 g sodium carbonate and 173 g sodium citrate dihydrate in a final volume of 850 mL water. Slowly, with stirring, add a solution of 17.3 g copper sulfate pentahydrate in 100 mL of water. Bring the final volume to one liter. The commercial reagent, at least, seems to be stable for years.
When 1 mL of reagent is heated with 5 drops of sample in a boiling water bath, a positive test for reducing sugars is formation of a precipitate within five minutes. The color ranges from green to yellow to orange to brick-red depending on the amount of reducing sugar in the sample; with a sample containing 1% glucose, the precipitate is usually brick-red.
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