In the ring test for identification of nitrate ion, what is the formula of the compound responsible for the brown ring formed at the interface of two liquids ?

Explanation

To identify the compound responsible for the brown ring formed at the interface of two liquids in the ring test for nitrate ions, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Ring Test**: The brown ring test is a qualitative analysis method used to detect the presence of nitrate ions (NO3⁻) in a solution.

2. **Reagents Used**: The main reagents involved in this test are:
- A solution containing nitrate ions, typically nitric acid (HNO3).
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