Biuret reagent
From Sciencemadness Wiki
The biuret test is a chemical test for proteins and polypeptides. It is based on the biuret reagent, a blue solution that turns violet upon contact with proteins, or any substance with peptide bonds. The test and reagent do not actually contain biuret; they are so named because both biuret and proteins have the same response to the test.
[HERE] is a ScienceMadness thread about making Biuret Reagent.