Potassium ferrocyanide is used in the detection of

Options

A. `Cu^(2+)` ion
B. `Fe^(3+)` ion
C. `Mn^(2+)` ions
D. Both A and B

Answer

To solve the question regarding the use of potassium ferrocyanide in detection, we can break down the information step by step.

### Step-by-Step Solution:

1. **Understanding Potassium Ferrocyanide**:
- Potassium ferrocyanide has the chemical formula K₄[Fe(CN)₆]. It contains iron (Fe) and cyanide (CN) ions.

2. **Reactions with Transition Metals**:
- Potassium ferrocyanide is known to react with various metal ions, particularly transition metals. The key reactions involve the formation of colored precipitates.

3. **Detection of Iron (Fe³⁺)**:
- When potassium ferrocyanide is added to a solution containing Fe³⁺ ions, it forms a precipitate known as Prussian blue (ferri-ferrocyanide). The appearance of a blue color indicates the presence of Fe³⁺ ions.

4. **Detection of Copper (Cu²⁺)**:
- If the solution contains Cu²⁺ ions, the reaction with potassium ferrocyanide results in a chocolate brown precipitate known as cupric ferrocyanide. The chocolate brown color indicates the presence of Cu²⁺ ions.

5. **Detection of Iron (Fe²⁺)**:
- In the case of Fe²⁺ ions, the reaction with potassium ferrocyanide produces a white precipitate. The formation of a white precipitate indicates the presence of Fe²⁺ ions.

6. **Summary of Detection**:
- From the above reactions, we can summarize that potassium ferrocyanide is used to detect:
- **Fe³⁺ ions** (Prussian blue precipitate)
- **Cu²⁺ ions** (Chocolate brown precipitate)
- **Fe²⁺ ions** (White precipitate)

### Conclusion:
Potassium ferrocyanide is primarily used in the detection of transition metals such as **Fe³⁺ and Cu²⁺ ions**.

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