A light bluish-green crystalline compound responds to the following tests:
(i). Its aqueous solution gives a brown precipitate on reaction with alkaline `K_2[HgI_4]` solution.
(ii). Its aqueous solution gives a blue colour with `K_3[Fe(CN)_6]` solution.
(iii). Its solution in hydrochloric acid gives a white precipitate with `BaCl_2` solution. Identify the ions present and suggest the formula of the compound.

Explanation

To solve the problem, we will analyze each of the tests provided for the light bluish-green crystalline compound step by step.

### Step 1: Analyze the first test
The first test states that the aqueous solution gives a brown precipitate when reacted with alkaline \( K_2[HgI_4] \) solution.

**Interpretation**:
- The formation of a brown precipitate indicates the presence of ammonium ions (\( NH_4^+ \)). This is a characteristic reaction where ammonium ions form a complex with mercury iodide.

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