Acids used to test gold purity are nitric acid and a mixture called aqua regia.
How Acids Test Gold
Gold testing involves using specific acids to verify the purity (karat) of gold. Different acids are used based on the expected purity of the gold being tested.
Here's a breakdown:
- Nitric Acid:
- Used to test gold that is 14 karat or lower.
- The acid's strength indicates the gold's purity.
- Lower karat gold will react (dissolve) more readily with nitric acid.
- Aqua Regia:
- A mixture of one part nitric acid and three parts hydrochloric acid.
- Stronger than nitric acid alone.
- Used to test gold with higher karat purity.
- The testing process involves comparison and elimination to determine the gold's karat.
| Acid Type | Purpose | Gold Purity Tested |
|---|---|---|
| Nitric Acid | Tests for lower karat gold purity. | 14k and Lower |
| Aqua Regia | Tests for higher karat gold purity. | Higher Karat Gold |
The Process Explained
- Application: A small amount of acid is applied to the gold piece.
- Observation: The reaction, or lack thereof, is observed.
- Analysis:
- If nitric acid dissolves the gold, the gold is likely 14k or lower.
- If aqua regia is required to dissolve the gold or a reaction is not observed, the gold is likely of higher purity.
- Comparison: Often, a comparison is made with known samples to finalize the karat reading.
Practical Insights
- Gold testing is used by jewelers, pawnbrokers, and other professionals to verify the gold’s value.
- The acids used are corrosive; professional equipment and handling are essential.
- Do not attempt to perform acid tests at home without proper safety knowledge and equipment.
