Which methods are usually employed for purifying the following metals :
(i) Nickel
(ii) Germanium

Explanation

To purify the metals Nickel and Germanium, the following methods are employed:

### Purification of Nickel:

1. **Mons Process**:
- Nickel is purified using the Mons process, which involves the formation of a volatile compound.
- Nickel is heated in the presence of carbon monoxide (CO) at a temperature of 330 to 350 Kelvin.
- This reaction produces nickel tetracarbonyl (Ni(CO)₄), a volatile compound.
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