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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. [ 1 ]
- Precursor Methods
- Circumstances and Methodology Behind The Marsh Test
- Specific Reactions Involved with The Marsh Test
- Effects of The Marsh Test
- References
The first breakthrough in the detection of arsenic poisoning was in 1775 when Carl Wilhelm Scheele discovered a way to change arsenic trioxide to arsine gas (AsH3), a garlic-smelling gas by treating it with nitric acid (HNO3) and combining it with zinc. In 1787, Johann Metzger discovered that if arsenic trioxide was heated in the presence of charco...
Even so, these tests have proven not to be sensitive enough. In 1832, a certain John Bodle was brought to trial for poisoning his grandfather by putting arsenic in his coffee. James Marsh, a chemist working at the Royal Arsenal in Woolwich was called by the prosecution to try to detect its presence. He performed the standard test by passing hydroge...
The Marsh test treats the sample with sulfuric acid and arsenic-free zinc. Even if there are minute amounts of arsenic present, the zinc reduces the trivalent arsenic (As3 + ). Here are the two half-reactions: 1. Oxidation: 2. Reduction: Overall, we have this reaction: But in an acidic medium, As3 + actually forms arsine gas (AsH3), so adding sulfu...
The case proved to be controversial, for it divided the country into factions who were convinced or otherwise of Mme. LaFarge's guilt; nevertheless, the impact of the Marsh test was great. The French press covered the trial and gave the test the publicity it needed to give the field of forensic toxicology the legitimacy it deserved, although in som...
Marsh J. (1836). "Account of a method of separating small quantities of arsenic from substances with which it may be mixed". Eddinburgh New Philosophical Journal 21: 229-236..Marsh J. (1837). "Arsenic; nouveau procédé pour le découvrir dans les substances auxquelles il est mêlé". Journal de Pharmacie 23: 553-562.(1837) "". Liebigs Annalen der Chemie 23: 207.Mohr C. F. (1837). "Zusätze zu der von Marsh angegebenen Methode, den Arsenik unmittelbar im regulinischen Zustande aus jeder Flüssigkeit auszuscheiden". Annalen der Pharmacie und Chemie 23: 217-225.The Marsh test is a laboratory test developed in the 19th century to check for traces of arsenic in a sample. It is named for James Marsh, the chemist who developed it in frustration because existing arsenic testing wasn’t always as sensitive as it needed to be.
Marsh test, method for the detection of arsenic, so sensitive that it can be used to detect minute amounts of arsenic in foods (the residue of fruit spray) or in stomach contents. The sample is placed in a flask with arsenic-free zinc and sulfuric acid.
Marsh went into his lab with one simple goal: develop a reliable and visually convincing method to detect arsenic in messy and complex samples like tissue and stomach contents. First, he turned to Scheele’s procedure in which arsenic was converted to arsine gas.
A chemical test for arsenic in which hydrochloric acid and zinc are added to the sample, arsine being produced by the nascent hydrogen generated. Gas from the sample is led through a heated glass tube and, if arsine is present, it decomposes to give a brown deposit of arsenic metal.
The Marsh Test in Fiction By the early 20th century the Marsh test was suffi-ciently well-known so as to make an appearance in several popular detective stories. In particular, it is mentioned in Dorothy L. Sayers’ 1930 novel Strong Poison, where it is performed by Lord Peter Whim-sey’s manservant, Bunter.
