Question

Observation of “Rhumann’s purple” is a confirmatory test for the presence of:

• A. Starch
• B. Reducing sugar
• C. Cupric ion
• D. Protein

Answer 1

The correct option is D Protein

Rhumann’s purple is ninhydrin. It is used to detect alpha-amino acid or carboxylic acid. When reacting with the free amines (proteins), a deep blue or purple color known as Ruhemann’s purple is produced. So observation of “Rhumann’s purple” is a confirmatory test for the presence of protein.
Hence option (d) is the answer.