Criminal Mischief Episode 16: Arsenic: An historical and modern poison

Suspense Radio

From HOWDUNNIT:FORENSICS

Toxicology is a relativelynew science that stands on the shoulders of its predecessors: anatomy,
physiology, chemistry, and medicine. Our knowledge in these sciences had toreach a certain level of sophistication before toxicology could become areality. It slowly evolved over more than two hundred years of testing,starting with tests for arsenic.

Arsenic had been a commonpoison for centuries, but there was no way to prove that arsenic was the
culprit in a suspicious death. Scientist had to isolate and then identify arsenic trioxide—the most common toxic form of arsenic— in the human body before arsenic poisoning became a provable cause of death. The steps that led to a reliable test for arsenic are indicative of how many toxicological procedures developed.

1775: Swedish
chemist Carl Wilhelm Scheele (1742–1786) showed that chlorine water would convert arsenic into arsenic acid. He then added metallic zinc and heated the mixture to release arsine gas. When this gas contacted a cold vessel, arsenic would collect on the vessel’s surface.

1787: Johann
Metzger (1739–1805) showed that if arsenic were heated with charcoal, a shiny, black “arsenic mirror” would form on the charcoal’s surface.

1806: Valentine
Rose discovered that arsenic could be uncovered in the human body. If the stomach contents of victims of arsenic poisoning are treated with potassium carbonate, calcium oxide, and nitric acid, arsenic trioxide results. This could then be tested and confirmed by Metzger’s test.

1813: French
chemist Mathieu Joseph Bonaventure Orfila (1787–1853) developed a method for isolating arsenic from dog tissues. He also published the first toxicological text, Traité des poisons (Treatise on Poison), which helped establish toxicology as a true science.

1821: Sevillas
used similar techniques to find arsenic in the stomach and urine of individuals who had been poisoned. This is marked as the beginning of the field of forensic toxicology.

1836: Dr.
Alfred Swaine Taylor (1806–1880) developed the first test for arsenic in human tissue. He taught chemistry at Grey’s Medical School in England and is credited with establishing the field of forensic toxicology as a medical specialty.

1836: James
Marsh (1794–1846) developed an easier and more sensitive version of Metzger’s original test, in which the “arsenic mirror” was collected on a plate of glass or porcelain. The Marsh test became the standard, and its principles were the basis of the more modern method known as the Reinsch test,
which we will look at later in this chapter. As you can see, each step in developing a useful testing procedure for arsenic stands on what discoveries came before. That’s the way science works. Step by step, investigators use what others have discovered to discover even more.

Acute vs. Chronic Poisoning ...