Carbohydrates And Benedict Test
Benedict’s test is a popular laboratory test to detect glucose present in the urine. It is named after the well known chemist Stanley Rossiter Benedict. He was an American. He developed the reagent called Benedict reagent that changes the color of the testing solution if glucose is present. The reagent consists of a mixture of sodium citrate, copper sulphate and sodium carbonate with a pH level of 10.5.
Benedict’s test is carried out to find out if a person has diabetes. Starch or complex carbohydrates or table sugar (sucrose) do not give direct results with this test. Apart from glucose, Benedict’s reagent detects reducing sugars and monosaccharides like maltose, lactose, galactose as well as mannose.
The procedure for conducting Benedict’s test is as follows. Add one ml of the liquid to be tested in a clean test tube. To this, add 5 ml of Benedict's reagent. Now place the test tube in a boiling water bath. Keep the tube immersed for about 3 minutes. Now remove it and keep it to cool. After a few minutes, you may see a colored formation of red, yellow or green precipitates. If the precipitate color is red, then the tested solution contains glucose. If it is any of color (that is yellow or green) then it is a different type of reducing sugar.
Sucrose or table sugar does not get identified by this solution. In order to test for the presence of sucrose, dilute hydrochloric acid has to be added to the testing liquid and heated before adding the Benedict’s reagent.
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