Prefiguring the Arsenic Wars

David S. Caudill

Benjamin Rush's 1805 work, Medical Inquiries and Observations, described a test that treated arsenic with alkaline copper sulfate to form a green precipitate.  Joseph Hume introduced his test in 1809, adding silver nitrate solution to arsenite precipitate. Robert Christison was known to use a test developed in 1785 by Samuel Hahnemann, the father of homeopathy.  This test involved passing a stream of sulfuretted hydrogen gas into previously acidified arsenic solution to produce a bright yellow arsenious sulfide precipitate. 

Marsh himself used other tests before arriving at his most famous one. In the 1833 trial of James Bodle, Marsh heated white arsenic to decompose it to oxygen and metallic arsenic, which would form a deposit on glass.  But his 1836 apparatus to capture arsenic was his most important. Numerous modifications followed, including the Marsh-Berzelius test, developed by Jöns Jacob Berzelius. 

Today atomic absorption spectrometry and inductively coupled plasma mass spectrometry are important forensic technologies for arsenic detection.

David Caudill, professor and Arthur M. Goldberg Family Chair in Law at Villanova University, was the 2007/2008 Société de Chimie Industrielle (American Section) Fellow at CHF.