MARTYN F. CHILLMAID / SCIENCE PHOTO LIBRARY MARTYN F. CHILLMAID / SCIENCE PHOTO LIBRARY
Biuret test. The purple ring at the top of the test tube indicates a positive result. The biuret test is a biochemical test for the presence of proteins (peptide bonds) in a solution. A positive result occurs when a purple ring appears after addition of copper (II) sulphate in alkaline solution.
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