Final answer:
The procedure includes layering the Biuret solution on top of the sample before mixing to observe any color change more easily and accurately.
Step-by-step explanation:
In the Biuret test for proteins, the procedure includes making observations with the Biuret solution as a layer on top of the sample before mixing. This is done to ensure that the reaction between the protein and Biuret solution occurs properly. The Biuret solution contains copper ions which react with the peptide bonds in the protein, resulting in the formation of a purple complex. By layering the Biuret solution on top of the sample, any color change can be observed more easily and accurately. This helps in determining the presence and concentration of proteins in the sample.