Why is it essential to boil off `H_(2)S` gas before proceeding to group III?

Explanation

### Step-by-Step Solution:

1. **Understanding the Role of H₂S in Qualitative Analysis**:
- In qualitative inorganic analysis, H₂S (hydrogen sulfide) is used to precipitate certain metal ions from solution. It is particularly useful for separating metal ions into different groups based on their solubility in sulfide form.

2. **Identification of Groups**:
- The metal ions are categorized into different groups based on their behavior with H₂S. Group III typically includes metals that form insoluble sulfides in the presence of H₂S, while Group IV includes metals that also form sulfides but under different conditions.

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