But did you know you can make your own Benedict's Solution with some everyday lab items? What are the ingredients of Benedict's Solution? To make ml of Benedict's solution, you will need Add 10g of Anhydrous Sodium Carbonate and continue stirring until the solid dissolves. Add Continue stirring to dissolve warming if necessary. Allow to cool to room temperature. Pour the solution into a suitable measuring cylinder and make up to ml Prepare five samples in 5 test tubes. The first sample is water.
The second sample is sucrose solution. The third sample is glucose solution. The fourth sample is hydrolysed sucrose solution, which can be obtained by heating a mixture with hydrochloric acid and sucrose, followed by neutralisation with soda. The fifth sample is a mixture of syrup with lemon and lime cordial. Heat the samples using a water bath. How it works The water is your control sample. Our bodies break down the sucrose into glucose and fructose through enzymes in our mouths and mostly in our small intestines Glucose, the third sample, is the sugar used by our bodies to make energy.
Even more generally, Benedict's test will detect the presence of aldehydes except aromatic ones , and alpha-hydroxy-ketones, including those that occur in certain ketoses. Thus, although the ketose fructose is not strictly a reducing sugar, it is an alpha-hydroxy-ketone, and gives a positive test because it is converted to the aldoses glucose and mannose by the base in the reagent.
Benedict's reagent can be prepared from sodium carbonate , sodium citrate and copper II sulfate. These are precipitated as red copper I oxide which is insoluble in water. To test for the presence of monosaccharides and reducing disaccharide sugars in food, the food sample is dissolved in water, and a small amount of Benedict's reagent is added.
The mixture is heated in a boiling water bath, and any precipitate formed is recorded as a positive result for the presence of reducing sugars in the food. The common disacharrides lactose and maltose are directly detected by Benedict's reagent, because each contains a glucose with a free reducing aldehyde moiety, after isomerization. Sucrose table sugar contains two sugars fructose and glucose joined with by their glycosidic bond in such a way as to prevent the glucose isomerizing to aldehyde, or the fructose to alpha-hydroxy-ketone form.
When reducing sugars are mixed with Benedicts reagent and heated, a reduction reaction causes the Benedicts reagent to change color. The color varies from green to dark red brick or rusty-brown, depending on the amount of and type of sugar.
This solution forms a copper thiocyanate precipitate which is white and can be used in a titration. This reaction is caused by the reducing property of simple carbohydrates.
The red copper I oxide formed is insoluble in water and is precipitated out of solution. This accounts for the precipitate formed. As the concentration of reducing sugar increases, the nearer the final colour is to brick-red and the greater the precipitate formed. Sometimes a brick red solid, copper oxide, precipitates out of the solution and collects at the bottom of the test tube. Sodium carbonate provides the alkaline conditions which are required for the redox reaction. Sodium citrate complexes with the copper II ions so that they do not deteriorate to copper I ions during storage.
Organic Molecules These are complex, carbon-containing molecules associated with living organisms. Most also contain hydrogen and oxygen. There are five major types: carbohydrates, lipids, proteins, nucleic acids, and vitamins. We covered the first three types in lab.
A review of our carbohydrate test data is provided on this page. Click the molecule types above to link to the associated review material. Interpreting Benedict's Reagent Results Benedict's reagent starts out aqua-blue. As it is heated in the presence of reducing sugars, it turns yellow to orange.
The "hotter" the final color of the reagent, the higher the concentration of reducing sugar. In general, blue to blue-green or yellow-green is negative, yellowish to bright yellow is a moderate positive, and bright orange is a very strong positive. See below. Bio L Index Page.
Lipid Tests.
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