Acid test (gold) mark is tested by applying aqua fortis (nitric acid), which dissolves the mark of any item that is not gold. If the mark remains, it is tested by applying aqua regia (nitric acid and hydrochloric acid). If the mark is removed, then this test dissolves the gold, proving the item to be genuine gold. More accurate testing of the item for its fineness or purity can be done through the use of differing strengths of aqua regia and comparative testing of gold items of known fineness. The figurative meaning of the expression, where it is applied to tests of character,
Acid Tests Acid Tests The Acid Tests were a series of parties held by author Ken Kesey primarily in the San Francisco Bay Area during the mid-1960s, centered entirely on the use of, and advocacy of, the psychedelic drug LSD, also known as "acid". LSD-25 was not made illegal in California until October 6, 1966. The name "Acid Test" was coined by Kesey, after the term "acid test" used by gold miners in the 1850s. He began throwing parties at his farm at La Honda, California. The Merry Pranksters were central to organizing the Acid Tests, including Pranksters such as Lee Quarnstrom