In which of the following `S-S` link is present ?

Options

A. Caro's acid
B. Dithionic acid
C. Thiosulphuric acid
D. Chlorosulphonic acid

Answer

To determine in which of the given acids the `S-S` (sulfur-sulfur) linkage is present, we will analyze the structures of each acid provided in the options.

### Step-by-Step Solution:

1. **Identify the Acids and Their Formulas**:
- **Carboxylic Acid**: General formula is RCOOH (not specified here).
- **Diethionic Acid**: H2S2O6.
- **Thiosulphuric Acid**: H2S2O3.
- **Chlorosulphonic Acid**: HSO3Cl.

2. **Analyze Carboxylic Acid**:
- The structure of carboxylic acid does not contain any sulfur atoms, hence it cannot have an `S-S` linkage.
- **Conclusion**: No `S-S` linkage in carboxylic acid.

3. **Analyze Diethionic Acid**:
- The structure of diethionic acid (H2S2O6) contains two sulfur atoms.
- When drawn, it shows a direct bond between the two sulfur atoms, indicating the presence of an `S-S` linkage.
- **Conclusion**: `S-S` linkage is present in diethionic acid.

4. **Analyze Thiosulphuric Acid**:
- The structure of thiosulphuric acid (H2S2O3) also contains two sulfur atoms.
- When drawn, it shows a direct bond between the two sulfur atoms, indicating the presence of an `S-S` linkage.
- **Conclusion**: `S-S` linkage is present in thiosulphuric acid.

5. **Analyze Chlorosulphonic Acid**:
- The structure of chlorosulphonic acid (HSO3Cl) contains only one sulfur atom.
- Therefore, it cannot have an `S-S` linkage as there are no two sulfur atoms present.
- **Conclusion**: No `S-S` linkage in chlorosulphonic acid.

### Final Answer:
The acids that contain the `S-S` linkage are:
- **Diethionic Acid (Option 2)**
- **Thiosulphuric Acid (Option 3)**