1950 - Arthur Jeffrey Dempster died.
Dempster was a Canadian-American physicist who designed and built the first mass spectrometer. Mass spectrometers are used to separate a sample's components by mass. He later used this device to discover the uranium isotope U-235, the main isotope used in atomic bombs.
1920 - Nicolaas Bloembergen was born.
Bloembergen is a Dutch-American physicist who shares half the 1981 Nobel Prize in Physics with Arthur Schawlow for the development of laser spectroscopy. Kai Siegbahn's research into the development of electron spectroscopy earned him the other half of the prize.
1892 - Archibald Scott Couper died.
James Irvine/Journal of Chemical Education (1930)Couper was a Scottish chemist who described the methods carbon atoms could bond together to form large molecules. He was also the first to describe molecules by element symbols connected by dashes to represent the bonds between the atoms.
1818 - Henri-Étienne Sainte-Claire Deville was born.
Deville was a French chemist who synthesized toluene and anhydrous nitric acid. He also developed the first economical process to produce aluminum.
1811 - Urbain Le Verrier was born.
Verrier was a French mathematician who predicted the existence of Neptune based on the irregularities of the orbit of Uranus. His calculations were used to discover Neptune within 1° of his predicted position. He also proposed the existence of a planet Vulcan inside the orbit of Mercury to explain Mercury's irregular orbit.