August 26 is Antoine Lavoisier’s birthday. Lavoisier was the French chemist considered the Father of Modern Chemistry.
Lavoisier was the man largely responsible for guiding chemistry from the hands of alchemists and into a scientific discipline. Prior to Lavoisier, those that studied chemical properties still worked under assumptions passed on from Medieval alchemists. Knowledge was recorded in arcane language and cryptic symbolism. One widely held belief of the time was the idea of phlogiston. Phlogiston was a component of fire and named after the Greek word for inflammable. Everything that could be burned contained phlogiston. Scientists saw that when something is burned, it weighed less afterward. This change in weight was due to the release of the burned object’s phlogiston to the air. The less residue left from burning, the more phlogiston was released. Phlogiston theory also explained why some metal calx (calx was the alchemical term we know today as an oxide) could be heated with charcoal and produce the original metal. The phlogiston from the charcoal was transferred to metal calx and produced the metal as a result. This led to one of the main problems with the theory. When metals are heated in air, the resulting calx weighed more than the original metal. According to theory, the metal should have released phlogiston to the air and weighed less, not more.
Lavoisier took a closer look at what happens when you burn things. His experiments showed combustion required air to occur. Joseph Priestley had recently found an interesting type of air he collected from heating mercury calx. Burning objects in this air would burn brighter and longer. Priestly felt his air caused this by being free of phlogiston, allowing the burning objects near it to give up their phlogiston easier. Lavoisier was intrigued by Priestley’s “dephlogisticated air”. His studies of Priestley’s air found it contained two components. One part would react with metal and supported respiration. The other part did not react with metal and worked as an asphyxiant. He later found that many acids contained the breathable part of this air. He named this part oxygène from the Greek ‘acid generator’. Lavoisier came up with his own theory of combustion that involved oxygen. The other air was found to be similar to Joseph Black’s “fixed air” found in weak alkaline substances.
One side effect of Lavoisier’s attack on phlogiston theory was showing water was not an element. Henry Cavendish was an English chemist who discovered “inflammable air”. This air would not burn unless it was mixed with normal air and then would burn violently and form a liquid. Testing showed this liquid was water. Lavoisier reacted inflammable air with pure oxygen and produced water. This showed water was made up of both oxygen and inflammable air. Lavoisier named this air hydrogène (water generator).
He denounced the idea of phlogiston and called on chemists to base their beliefs on observation, not stories. His textbook Traité élémentaire de Chimie (Elementary Treatise of Chemistry) outlined theories of light, caloric combustion, and a list of simple substances which was the first listing of chemical elements. It also contained one of the first laws of conservation of mass. When a reaction takes place, nothing is gained, nothing is lost, everything is transformed. Lavoisier introduced new nomenclature to chemistry worked out with other notable French chemists. Terms like oxides replaced the old term calx. Degrees of oxidation of acids would contain the suffix -ic and -ous like sulfuric or sulfurous acid. Salts formed from these acids would gain -ate and -ite like copper sulfate and copper sulfate. This textbook became a standard for any student serious about the study of chemistry.
Lavoisier was also involved in politics. One of his roles in France was a tax collector. He also took a stand to defend foreign-born scientists from a mandate to forfeit their freedom and possessions. Both of these were not looked kindly upon by the new post-Revolution government and he was branded a traitor. He was tried, convicted and guillotined all on the same day. Citing Lavoisier’s contribution to French science, clemency was asked for, but the judge responded, “The Republic needs neither scientists nor chemists; the course of justice cannot be delayed.”
Within two years, he was exonerated of all charges and honored for his achievements.
Notable Science Events for August 26
1998 – Frederick Reines died.
Reines was an American physicist who was awarded half the 1995 Nobel Prize in Physics for his and Clyde Cowan’s detection of the neutrino. A neutrino is a chargeless and nearly massless elementary particle that travels close to the speed of light. They were postulated to exist in 1934 to account for the slight difference in mass during some radioactive decays and nuclear reactions. The actual detection of a neutrino wasn’t announced until 1956.
1997 – Louis Essen died.
Essen was a British physicist who developed methods to precisely measure the passing of time. He developed the quartz crystal ring clock with an accuracy of one-second loss in three years. He also developed the first atomic clock with Jack Parry. Their clock used the natural resonance frequency of cesium atoms and would be accurate to one second in 2000 years. Clocks based on this design would be used to define the SI standard of the second used today.
1987 – Georg Wittig died.
Wittig was a German chemist who was awarded half the 1979 Nobel Prize in Chemistry for his work with organic phosphorus compounds. He found that phosphorus ylides could be used as a catalyst to change aldehyde or ketone into an alkene and a triphenylphosphine oxide. This reaction is known as the Wittig reaction.
1895 – Johann Friedrich Miescher died.
Miescher was a Swiss physician and biochemist who was the first to isolate nucleic acids. He isolated these from the nucleus of white blood cells. Miescher investigated the chemistry of nucleic acids, but never determined their purpose or function.
Nucleic acids would eventually be determined to be the basic carriers of genetic inheritance.
1882 – James Franck was born.
Franck was a German physicist who shared the 1925 Nobel Prize in Physics with Gustav Ludwig Hertz for their experiment to confirm the Bohr model of the atom.
The Franck-Hertz experiment used a vacuum tube to shoot electrons through a thin vapor of mercury. They found the electrons lost energy as they collided with the mercury atoms. This energy loss was expected, but the interesting part was the energy loss occurred at discrete quantized levels. The same levels predicted by the Bohr model of the atom.
1743 – Antoine-Laurent Lavoisier was born.
1723 – Anthonie van Leeuwenhoek died.
Leeuwenhoek was a Dutch natural philosopher who is considered the “Father of Microbiology”.
He was the first to use the microscope to observe and describe single-celled organisms, or as he called them, animalcules. He also recorded microscopic observations of bacteria, spermatozoa, the banded pattern of muscle fibers and capillary blood flow.