is the birthday of Friedrich Paneth, an Austrian chemist who helped develop radioactive tracer techniques widely used in science, engineering, and medicine.
In 1912, Paneth and George Charles de Hevesy showed how radioactive isotopes could be used to mark a compound without altering its chemical or physical properties and then trace it as it underwent a chemical reaction or traveled through an organism or machine. The technique made it possible to study distribution patterns and transport rates of molecules, for instance in blood. Paneth is also known for proving the existence of methyl and ethyl free radicals, highly reactive and short-lived chemical intermediates involved in many chemical reactions. He died in 1958.
[Source: Britannica Online]