<P> 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 . </P> <P> Arsenic, in the form of white arsenic trioxide As 2O 3, was a highly favored poison, for its odourlessness, 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 will have symptoms similar to cholera . </P> <P> 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 (AsH), by treating it with nitric acid (HNO) and combining it with zinc . </P> <Dl> <Dd> As O + 6 Zn + 12 HNO → 2 AsH + 6 Zn (NO) + 3 H O </Dd> </Dl>

Who devised the first test for detection of arsenic in 1775