Question

The Marsh test, developed in the mid-1830s and used until the 1970s, detected arsenic in a poisoned substance by mixing the substance with _____ and _____, then heating it to determine whether a metallic deposit would form.

Answer 1

The poisoned substance was mixed with arsenic-free zinc and sulfuric acid, resulting in arsine gas.

The gas was later ignited and decomposed into pure metallic arsenic. This test was highly sensitive and could detect even one-fiftieth of a milligram of arsenic. It was a remarkable discovery, since before that, arsenic was widely used as poison in enormous amounts of murders, impossible to detect and trace.