Today In Science History – August 21 – Jean Servais Stas 1


Jean Servais Stas

Jean Servais Stas (1813-1891) Belgian Chemist Credit: OEuvres Complètes, Jean Baptiste Depaire, 1894

August 21 is Jean Servais Stas’ birthday. Stas was a Belgian doctor turned chemist known for his work on atomic weights.

His atomic weight work began in 1835 while working in Jean-Baptiste Dumas’ laboratory. Dumas is also known for his work determining atomic weights and molecular weights by their vapor densities. Stas set to work on finding the atomic weight of carbon. He measured a sample of pure carbon and burned it in a known volume of pure oxygen. Once the sample was completely consumed, he weighed the amount of carbon dioxide produced and the remaining amount of oxygen. He set the atomic weight of oxygen to 16 and calculated the mass of carbon relative to this weight. The value he arrived at turned out to be the most accurate to date.

This work earned him a professorship at the Royal Military School in Brussels. While here, he continued his work with other pure elements. He improved his technique and established a greater accuracy than any other attempts at determining atomic weights. His work was accurate enough to disprove the popular theory of William Prout. Prout’s theory held an element’s atomic weight was integer multiples of the atomic weight of hydrogen. Stas’ work became the standard values for other chemists.

Stas is also famous for being one of the first chemists to perform forensic toxicology. In 1850, Belgian Count Hypolyte Visart de Bocarmé was under suspicion of poisoning his brother-in-law Gustave Fougnies. The Belgian authorities believed Bocarmé isolated nicotine from tobacco leaves and the pure substance to Fougnies, but there was no concrete proof. Stas was asked if he could help. He developed a procedure to separate alkaloids from human tissue using alcohols. This was the first time this had been done successfully. Stas’ tests showed there was a substantial amount of nicotine in Fougnies’ organs. This was enough to land Bocarmé in prison for the murder.

Other Notable Science Events for August 21

1995 – Subrahmanyan Chandrasekhar died.

Chandrasekhar was an Indian-born American astrophysicist who was awarded half the 1983 Nobel Prize in Physics for his theories of the evolution and structure of stars. He demonstrated the upper limit, or Chandrasekhar limit, of the mass of a white dwarf star. He also studied the theories of gravitational waves, black holes, and stellar dynamics.

The orbiting X-ray telescope deployed by the Space Shuttle Challenger is named the Chandra X-Ray Observatory in his honor.

1993 – Mars Observer lost.

Mars Observer

Mars Observer. Jet Propulsion Laboratory

NASA lost communication with the Mars Observer satellite just three days prior to its insertion into Mars orbit. It is believed the most probable cause was a rupture in the fuel pressurization side of the spacecraft’s propulsion system. This would cause the fuel prematurely mix with the oxidizer and cause the satellite to spin out of control.

1814 – Benjamin Thompson died.

Benjamin Thompson (1753 - 1814)

Benjamin Thompson (1753 – 1814)

Thompson was a British physicist who made significant contributions to early thermodynamics. He determined a method to measure the specific heat of solids independently of Johan Wilcke. He also related mechanical work with heat.

Thompson introduced the unit of light called ‘candle’. It was equivalent to the brightness of a candle. Today, the SI unit of luminosity is the candela. One candle = 0.981 candelas.

1813 – Jean Servais Stas was born.


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