Vallium is used as tranquilizer/antimicrobial.

Explanation

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks whether Vallium is used as a tranquilizer or an antimicrobial agent. We need to clarify the role of Vallium in medical use.

2. **Identifying Vallium**: Vallium is a brand name for the drug Diazepam, which is primarily known for its use as a tranquilizer. It is classified as a benzodiazepine.

3. **Function of Vallium**: Diazepam (Vallium) is used to treat anxiety, muscle spasms, and seizures. It works by enhancing the effects of a neurotransmitter called gamma-aminobutyric acid (GABA) in the brain, leading to a calming effect.

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