In the manufacture of metallic sodium by the fused salt electrolysis `(` Down's process ) a small amount of `CaCl_(2)` is added to `:`

Options

A. Imrove the electrical conduction
B. Decrease the melting temperature
C. Stabilising the metallic sodium
D. Increase the temperature of electrolysis

Explanation

To solve the question regarding the addition of calcium chloride (CaCl₂) in the manufacture of metallic sodium by fused salt electrolysis (Down's process), we can break down the explanation into clear steps:

### Step-by-Step Solution:

1. **Understanding the Down's Process**:
- The Down's process is a method used to produce metallic sodium by the electrolysis of molten sodium chloride (NaCl).

2. **Role of Electrolysis**:
- During electrolysis, NaCl is melted to allow the ions to move freely. The process involves the decomposition of NaCl into sodium (Na⁺) and chloride ions (Cl⁻).

3. **High Temperature Requirement**:
- The melting point of sodium chloride is approximately 1075 K. To carry out electrolysis efficiently, the temperature must be maintained high enough to keep the NaCl in a molten state.

4. **Addition of Calcium Chloride**:
- A small amount of calcium chloride (CaCl₂) is added to the molten NaCl. The purpose of this addition is to lower the melting point of the mixture.

5. **Effect on Melting Point**:
- The addition of CaCl₂ lowers the melting point of the salt mixture from around 1075 K to approximately 850-875 K. This reduction in temperature makes the process more energy-efficient.

6. **Energy Efficiency**:
- By lowering the melting point, less energy is required to maintain the molten state of the salt, which is crucial for the economic viability of the sodium production process.

7. **Conclusion**:
- Therefore, the primary reason for adding CaCl₂ in the Down's process is to reduce the melting temperature of the sodium chloride, facilitating a more efficient electrolysis process for the production of metallic sodium.