This practice is a destructive method employed to ascertain the authenticity and karat value of gold items. It involves applying nitric acid to a scratch made on a testing stone with the gold object. The reaction, or lack thereof, indicates the gold’s purity. For instance, if an item represented as 18 karats resists dissolution by an acid solution formulated for that specific karat, it suggests the item is truly 18 karats gold or higher.
The value of this technique lies in its relatively quick and inexpensive method for verifying gold content. Historically, it provided a practical means for jewelers, pawnbrokers, and gold buyers to assess the value of precious metal items before advanced analytical instrumentation became readily available. While other methods exist today, this remains a convenient preliminary assessment tool.