|
The Marsh test is a highly sensitive method in the detection of arsenic, especially useful in the field of forensic toxicology when arsenic was used as a poison. It was developed by the chemist James Marsh and first published in 1836. Arsenic, in the form of white arsenic trioxide As2O3, was a highly favored poison, for it is odorless, easily incorporated into food and drink, and before the advent of the Marsh test, untraceable in the body. In France, it came to be known as ''poudre de succession'' ("inheritance powder"). For the untrained, arsenic poisoning would have symptoms similar to cholera. == Precursor methods == The first breakthrough in the detection of arsenic poisoning was in 1775 when Carl Wilhelm Scheele discovered a way to change arsenic trioxide to garlic-smelling arsine gas (AsH3), by treating it with nitric acid (HNO3) and combining it with zinc. :As2O3 + 6 Zn + 12 HNO3 → 2 AsH3 + 6 Zn(NO3)2 + 3 H2O In 1787, Johann Metzger discovered that if arsenic trioxide was heated in the presence of charcoal, a shiny black powder (arsenic mirror) would be formed over it. This is the reduction of As2O3 by carbon: : 2 As2O3 + 3 C → 3 CO2 + 4 As In 1806, Valentin Rose took the stomach of a victim suspected of being poisoned and treated it with potassium carbonate (K2CO3), calcium oxide (CaO) and nitric acid. Any arsenic present would appear as arsenic trioxide and then could be subjected to Metzger's test. However, the most common test (and used even today in water test kits) was discovered by Samuel Hahnemann. It would involve combining a sample fluid with hydrogen sulfide (H2S) in the presence of hydrochloric acid (HCl). A yellow precipitate, arsenic trisulfide (As2S3) would be formed if arsenic was present. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Marsh test」の詳細全文を読む スポンサード リンク
|