Marsh, James

9/2/1794–6/21/1846
ENGLISH
CHEMIST

With a distinguished career as an English chemist in the 1830s and 1840s, James Marsh (1794–1846) is historically well-known for the research and development of a dependable, simple laboratory test for the identification of minute traces of arsenic. The Marsh test (or the Marsh Arsenic test), as it is known today, involved the testing of given samples of food, fluid, or deceased human tissue by forensic toxicologists from the middle part of the nineteenth century to well into the latter half of the twentieth century. In fact, the test was often used by Mathieu Joseph Bonaventure Orfila (1787–1853), the person who is often considered as the originator of forensic toxicology . The Marsh test gave experts an effective and accurate way to detect small amounts of arsenic—a sometimes-fatal chemical contaminant when placed accidentally or intentionally within the body. In Marsh's day, arsenic poisoning was a very large problem throughout the world, and was often not discovered by ordinary analysis. The development of this testing method and accompanying apparatus by Marsh helped to promote the scientific advancements of poisoning investigations, along with assisting the outcome of several notable murder trials.

Little is known about Marsh as he grew up in England and began his professional career at the Royal British Arsenal (also called the Woolwich Arsenal), which was located east of London in the town of Woolwich. His scientific abilities were probably first noticed in 1836 when leaders of the neighboring town of Plumstead asked advice of him as to the possible reason of arsenic poisoning within the deceased body of a local leader. As a qualified chemist who was familiar with the accepted German methods of testing autopsies, Marsh applied yellow precipitates, ammonia solvents, and various other laboratory materials to the tissues of the dead body and to the coffee that was alleged to have contained the poison. Marsh presented his evidence at the inquest, which clearly identified arsenic in the victim's body. However, at the trial the jury did not understand his technical testimony and acquitted the accused grandson of the decedent. (The grandson later confessed to the crime after being convicted of later wrongdoings.) Because of this work, Marsh is considered today as the first person to present the results of toxicology analysis in court.

Because of his inability to convince the jury, Marsh became determined to develop new laboratory tests that could prove the presence of even small traces of arsenic and make the results understandable to even uninformed people. Basing his investigations on the previous work (of transforming arsenic to a related gas called arsine) by Swedish scientist Karl Wilhelm Scheele (1742–1786), Marsh produced hydrogen from a reaction of adding solid zinc metal to a glass receptacle containing either hydrochloric acid or sulfuric acid. When Marsh added tissue or body fluid to the hydrogen-generating container, its reaction with the zinc and acid would create hydrogen gas. If any type of arsenic was present, the hydrogen gas when heated by Marsh would react with it to produce arsine gas, which fumed off to deposit a silvery-black film—that is, metallic arsenic—on a porcelain bowl.

Marsh was able to produce visible stains on the bowl when only very small amounts of arsenic were present. In fact, as little as 0.1 milligrams (0.0000035 ounces) of arsenic were detected by using the test designed by Marsh. Later, Marsh designed a U-shaped glass tube with a narrowed nozzle at one end to provide a controlled reaction and to help ignite the exiting gas. Marsh wrote a report based on his pioneering research and resulting test that was published in the Edinburgh Philosophical Journal in October 1836, and followed with two other Marsh test articles in 1837 and 1840.

Upon publication of the article, toxicologists and other scientists around the world experimented with the information that Marsh provided. French toxicologist Orfila, already famous in his own right, made important improvements to the Marsh test such as recommending that all reacting chemicals be shown free of arsenic before being used in an investigation. In 1840, the Marsh test was instrumental in making a conviction in a major murder case, one that was decided by a report by Orfila. Specifically, Orfila applied the Marsh test to decide the controversial trial of Marie Lafarge, who was charged with murder in the arsenic poisoning of her husband. Based on his results, Lafarge was found guilty and sentenced to death (which was later reduced to life in prison). Due to the scientific work of Orfila and his expert application of the Marsh test, procedures were first formalized for proving poisoning in court cases with the use of toxicological analysis .

Throughout his career, Marsh worked at the Woolwich arsenal where he was employed in the fields of electromagnetism and artillery technology. While still employed at the arsenal, March died in London at the age of 51. After his death, the Marsh test was extensively applied by forensic toxicologists until more technically-advanced methods of instrumental analysis such as atomic absorption spectroscopy and x-ray fluorescence spectroscopy replaced it in the latter half of the twentieth century.

see also Autopsy; Toxicological analysis.