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,
Nucleic acid test Nucleic acid test A nucleic acid test (NAT) or nucleic acid amplification test (NAAT) is a technique utilized to detect a particular nucleic acid, virus, or bacteria which acts as a pathogen in blood, tissue, urine, etc. The NAT system differs from other tests in that it detects genetic materials rather than antigens or antibodies. Detection of genetic materials allows an early diagnosis of a disease because the detection of antigens requires time for antigens to appear in the bloodstream. Since the amount of a certain genetic material is usually very small, NAT includes an amplification step of the genetic