One day Kavita went to a jewellers shop with her mother. Her mother gave an old metal jewellery to the goldsmith to polish. Next day when they brought the jewellery back, they found that there was a slight loss in its weight. Can you suggest a reason for the loss in weight?

Explanation

**Step-by-Step Solution:**

1. **Understanding the Context**: Kavita and her mother took an old metal jewelry piece to a goldsmith for polishing. After polishing, they noticed a slight loss in weight of the jewelry.

2. **Polishing Process**: The goldsmith uses specific methods to polish jewelry, which often involves cleaning agents or acids to remove tarnish and dirt.

3. **Use of Acids**: One common cleaning solution used by goldsmiths is called Aqua Regia. Aqua Regia is a mixture of hydrochloric acid (HCl) and nitric acid (HNO3). It is known for its ability to dissolve metals like gold, silver, and copper.

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