The reagent used for detection of protein is

Options

A. `"Conc." HNO_(3)`
B. Fehling's solution
C. Tollen's reagent
D. Baeyer's reagent

Answer

**Step-by-Step Solution:**

1. **Understanding the Question:**
The question asks for the reagent used for the detection of proteins. Proteins are made up of long chains of amino acids.

2. **Identifying the Reagents:**
The options provided are:
- Concentrated HNO3
- Felling solution
- Toluene's reagent
- Bayer's reagent

3. **Analyzing Each Reagent:**
- **Concentrated HNO3:** This is a strong nitrating agent and is known to react with aromatic amino acids, leading to the formation of a yellow color, indicating the presence of proteins.
- **Felling solution:** This reagent is used to distinguish between ketones and aldehydes, not for protein detection.
- **Toluene's reagent:** This reagent is not typically used for protein detection.
- **Bayer's reagent:** This reagent is used to detect unsaturation in organic compounds, not proteins.

4. **Performing the Xanthoproteic Test:**
To confirm the presence of proteins, the xanthoproteic test is performed:
- Take a clean and dry test tube.
- Add the sample suspected to contain protein.
- Add concentrated nitric acid to the sample.
- Shake the test tube gently.
- Heat the mixture gently.
- Observe for a yellow color, which indicates the presence of proteins due to the formation of nitro derivatives.

5. **Conclusion:**
Based on the analysis, the correct reagent for the detection of proteins is **concentrated HNO3**.

**Final Answer:** The reagent used for the detection of protein is concentrated HNO3.

---