An organic compound containing sulphur is estimated by Carius method in which fuming `HNO_3` is used to convert S into

Options

A. `SO_3^(2-)`
B. `SO_4^(2-)`
C. `SO_3`
D. `SO_2`

Explanation

To solve the question regarding the estimation of an organic compound containing sulfur using the Carius method, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Carius Method**: The Carius method is a technique used to determine the amount of sulfur in organic compounds. In this method, the organic compound is treated with fuming nitric acid (HNO3) in a sealed tube.

2. **Reaction with Fuming HNO3**: When the organic compound containing sulfur is heated with fuming HNO3, the sulfur present in the compound is oxidized. Fuming HNO3 is a strong oxidizing agent that facilitates this conversion.

3. **Conversion of Sulfur**: The sulfur in the organic compound is converted to sulfuric acid (H2SO4) during the reaction. This is a crucial step because the amount of sulfuric acid formed can be quantitatively measured.

4. **Chemical Equation**: The reaction can be summarized as follows:
\[ \text{S (from organic compound)} + \text{HNO}_3 \rightarrow \text{H}_2\text{SO}_4 \]
This indicates that sulfur is oxidized to form sulfuric acid.

5. **Identifying the Anionic Part**: Since the question specifically asks for the product formed from sulfur in terms of its anionic part, we need to focus on the sulfate ion (SO4^2-). The sulfuric acid dissociates into:
\[ \text{H}_2\text{SO}_4 \rightarrow 2\text{H}^+ + \text{SO}_4^{2-} \]

6. **Conclusion**: Therefore, the sulfur in the organic compound is converted into the sulfate ion (SO4^2-) when using the Carius method with fuming HNO3.

### Final Answer:
The sulfur in the organic compound is converted into sulfate ion (SO4^2-) during the Carius method.