Which of the following tests is not used for testing proteins :

Options

A. Molisch's test
B. Biuret test
C. Ninhydrin test
D. Millon's test

Answer

To determine which of the following tests is not used for testing proteins, we will analyze each option provided: Mollish test, Biuret test, Ninhydrin test, and Mylan's test.

### Step-by-Step Solution:

1. **Mollish Test**:
- The Mollish test is primarily used for detecting carbohydrates.
- It involves the dehydration of carbohydrates by sulfuric acid, which produces an aldehyde that condenses with phenol to form a violet ring.
- Since this test is specific for carbohydrates, it is not used for testing proteins.

2. **Biuret Test**:
- The Biuret test is used to detect the presence of peptide bonds, which are characteristic of proteins.
- In this test, a copper(II) ion forms a violet-colored coordination complex in an alkaline solution when peptide bonds are present.
- Therefore, this test is indeed used for testing proteins.

3. **Ninhydrin Test**:
- The Ninhydrin test is used to detect alpha-amino acids and proteins that contain a free amino group.
- It gives a positive result for amino acids, which are the building blocks of proteins.
- Hence, this test is also used for testing proteins.

4. **Mylan's Test**:
- Mylan's test is an analytical method used to detect soluble proteins.
- When Mylan's reagent is added to a protein solution and heated, it produces a reddish-brown precipitate, indicating the presence of tyrosine residues, which are found in nearly all proteins.
- Thus, this test is also used for testing proteins.

### Conclusion:
After analyzing all the tests, we find that the **Mollish test** is the only test that is not used for testing proteins. Therefore, the correct answer is:

**Mollish Test**.

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