Tests

• Benedict’s test for reducing and non-reducing sugars - a reducing sugar is one which can donate electrons and includes all monosaccharides and some disaccharides
• Benedict's Test: alkaline solution of blue copper (II) sulphate is added to the sugar and subsequently heated, in the presence of reducing sugar, a red precipitate of copper (I) oxide is formed. In the absence of reducing sugar, the Benedict’s reagent does not change colour.
• The biuret test is used to test for proteins
• Beirut Test: Firstly, a sample of the solution is placed in a test tube and subsequently an equal amount of NaOH is added. Afterwards, a few drops of dilute copper (II) sulfate solution is added and gently mixed.
• Beirut Test: In the presence of a protein, the solution turns lilac/ as an indicator of peptide bonds. In the absence of protein, the solution remains blue.
• The emulsion test is used to test for lipids
• Emulsion Test: Firstly, 2ml of sample is added to 5ml of ethanol. Subsequently, the contents are mixed thoroughly by shaking to ensure that the lipids dissolved.
• Emulsion Test: Upon addition of 5ml of water and mixing, the solution turns cloudy indicating the presence of lipid due to the formation of an emulsion where the

  light is refracted as it passes from droplets of oil to droplets of water.
• Starch is tested for with the help of iodine – in the presence of starch, the colour of potassium iodide solution from yellow to black/blue.