(vii) Mercury is transported on containers made of iron.

Explanation

**Step-by-Step Solution:**

1. **Understanding Mercury's Properties:**
- Mercury (Hg) is a metal that is liquid at room temperature. This unique property makes it necessary to use specific materials for its transportation.

2. **Health Risks Associated with Mercury:**
- Mercury is toxic, and exposure can lead to serious health issues. Therefore, it is crucial to transport it safely to prevent any leaks or contamination.

3. **Choosing the Right Container Material:**
- When transporting mercury, the container material must not react with it or allow it to amalgamate. Amalgamation is the process where mercury forms an alloy with other metals, which can lead to contamination or loss of mercury.

4. **Identifying Suitable Materials:**
- The two materials that do not amalgamate with mercury are iron and platinum. These materials are chosen for their inertness with respect to mercury.

5. **Conclusion:**
- Therefore, mercury is transported in containers made of iron because it does not react with or amalgamate with mercury, ensuring safe transportation.

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