Ethers in contact with air for a long time form peroxides. The presence of peroxide in ether can be tested by adding `Fe^(2+)` ions in it and then

Options

A. KCNS is added
B. `SnCl_(2)` is added
C. `HgCl_(2)` is added
D. KI is added

Explanation

To test for the presence of peroxides in ethers, follow these steps:

### Step-by-Step Solution:

1. **Understanding the Formation of Peroxides:**
- Ethers, when left in contact with air (which contains oxygen) for a long time, can form peroxides. For example, diethyl ether (C2H5)2O can form a peroxide linkage (–O–O–).

2. **Adding Ferrous Ions (Fe²⁺):**
- To test for the presence of peroxides, you start by adding ferrous ions (Fe²⁺) to the ether solution. The peroxides will oxidize the ferrous ions (Fe²⁺) to ferric ions (Fe³⁺).

3. **Formation of Ferric Ions:**
- The reaction between peroxides and ferrous ions results in the formation of ferric ions (Fe³⁺). This is a crucial step in the testing process.

4. **Adding Potassium Thiocyanate (KSCN):**
- After the oxidation of Fe²⁺ to Fe³⁺, you then add potassium thiocyanate (KSCN) to the solution.

5. **Formation of a Red Complex:**
- The ferric ions (Fe³⁺) react with thiocyanate ions (SCN⁻) to form a red-colored complex known as ferric thiocyanate (Fe(SCN)³). The appearance of this red color indicates the presence of peroxides in the ether.

6. **Conclusion:**
- Therefore, the presence of peroxides in ethers can be confirmed by the addition of KSCN after adding Fe²⁺, which results in a red-colored solution.

### Final Answer:
The correct option is **A) KSCN is added**.