Presence of peroxide in ethers of old stock can be tested by first treating them with `FeSO_4` solution and then adding an aqueous solution of ………&from red colour solution

Options

A. `SnCl_2`
B. `HgCl_2`
C. `KI`
D. `KCNS`

Answer

To determine the presence of peroxides in ethers from old stock, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Problem**:
- Ethers, particularly when stored for a long time, can react with oxygen in the air to form peroxides. These peroxides can be hazardous and explosive.
- We need a method to test for the presence of these peroxides in ethers.

2. **Initial Treatment with FeSO4**:
- Begin by treating the ether sample with a solution of ferrous sulfate (FeSO4).
- This step is crucial because FeSO4 contains Fe²⁺ ions, which will react with the peroxides present in the ether.

3. **Adding Potassium Thiocyanate**:
- After treating the ether with FeSO4, the next step is to add an aqueous solution of potassium thiocyanate (KSCN).
- The potassium thiocyanate will react with the iron ions that were formed during the previous step.

4. **Observation of Color Change**:
- If peroxides are present in the ether, the reaction between Fe²⁺ ions from FeSO4 and the thiocyanate ions from KSCN will produce a red-colored complex (iron thiocyanate).
- The formation of this red color indicates the presence of peroxides in the ether.

5. **Conclusion**:
- Therefore, the presence of peroxide in ethers of old stock can be tested by first treating them with FeSO4 solution and then adding an aqueous solution of potassium thiocyanate, which results in a red color solution.

### Final Answer:
The answer is: **Potassium thiocyanate (KSCN)**.

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