James Marsh (1794-1846)
Overview
James Marsh (September 2, 1794-June 21, 1846) was an English chemist who developed the Marsh Test for detecting arsenic. He was inspired to develop the test, which was highly sensitive for the time (detecting as little as one-fiftieth of a milligram), after a criminal trial where he was unable to prove that a victim was poisoned by arsenic due to poor testing methods. In his new test, Marsh combined a sample containing arsenic with sulfuric acid and arsenic-free zinc, which produced gas. He would burn off the gas, which would leave behind pure metallic arsenic. The arsenic would then appear as a black streak after it was passed over a cool surface.