There are following extraction process of silver but not:

Options

A. as a side product in electrolytic refining of copper
B. Parke's process in which Zn is used to extract silver by solvent extraction from molten lead
C. by reaction of silver sulphide with KCN and then reaction of soluble complex with Zn
D. by heating `Na[Ag(CN)_(2)]`

Answer

To determine which of the listed processes is not an extraction method for silver, we need to analyze the options provided.

### Step-by-Step Solution:

1. **Understanding the Extraction Processes**:
- Silver can be extracted through various methods, including electrolytic refining, the Parkes process, and reactions involving cyanides.

2. **Analyzing the Options**:
- **Option A**: As a side product in electrolytic refining of copper.
- This is a valid method as silver can be recovered during the refining of copper.
- **Option B**: Parkes process using Zn to extract silver from molten lead.
- This is also a valid method, as the Parkes process is specifically designed for the extraction of silver from lead ores.
- **Option C**: Heating NaAgCN2.
- This option does not represent a known extraction method for silver. Instead, it suggests a process that does not effectively extract silver.
- **Option D**: MacArthur-Forrest process.
- This process is known for extracting gold, not silver, from ores using cyanide solutions.

3. **Conclusion**:
- The correct answer is **Option C**: Heating NaAgCN2 is not a recognized extraction process for silver.

### Final Answer:
The extraction process of silver that is not valid is **D: Heating NaAgCN2**.