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,
Meconic acid Meconic acid Meconic acid, also known as acidum meconicum and poppy acid, is a chemical substance found in certain plants of the Papaveraceae family (poppy) such as "Papaver somniferum" (opium poppy) and "Papaver bracteatum". Meconic acid constitutes about 5% of opium and can be used as an analytical marker for the presence of opium. Meconic acid has erroneously been described as a mild narcotic, but it has little or no physiological activity, and is not used medicinally. Meconic acid forms salts with alkaloids and metals. These salts as well as meconic acid esters are called meconates. Meconic acid was first