The Biuret test is a chemical test used to detect the presence of proteins in a sample. It involves adding a solution of sodium hydroxide and copper sulfate to the sample. If proteins are present, the solution changes color to purple, indicating a positive result. This reaction occurs because the copper ions in the solution bind to the peptide bonds in proteins. This test is commonly used in laboratories for protein analysis in various fields, including biochemistry and food science. The intensity of the purple color can also provide an estimate of the protein concentration in the sample, making it a useful tool for researchers and scientists.