State one relevant observation for the following:
Platinum is added to aqua-regia.

Explanation

To answer the question regarding the observation when platinum is added to aqua regia, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Aqua Regia**:
Aqua regia is a highly corrosive mixture of concentrated nitric acid (HNO3) and concentrated hydrochloric acid (HCl). It is known for its ability to dissolve noble metals, including gold and platinum.

**Hint**: Remember that aqua regia is a mixture of two strong acids.
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