How to recognize gold using acids?
To recognize gold, it is possible to use a chemical identification method based on strong acid, which allows to distinguish pure gold from other common metals.
The acid kit consists of different bottles and a touchstone, also called a touchau. To use it, the jewel is rubbed firmly on the stone, then a few drops of the acid corresponding to the supposed carat of the jewel are placed (9 carats, 14 carats, 18 carats or 22 carats).
If no reaction occurs, the jewel is gold and of a corresponding title .
If the trace disappears, the jewel is not gold.
If the trace turns red, the degree of purity is lower than that of the acid used.
The nitric acid present in the bottles must be handled with extreme caution.
Wearing suitable gloves and goggles is strongly recommended.
A real touchstone is needed in order to obtain an indisputable answer.
Note: The acid can also be applied directly to the jewelry after scratching its surface.
Information and visuals collected on the website of the Bureau des Poinçons de la Douane - Garantie de Paris
https://www.douane.gouv.fr
https://www.goldinfo.fr/
