April - 75 years ago, 90 years ago, 95 years ago, 100 years ago, 105 years ago

The first synthetic rubber was produced when Arnold M Collins isolated chloroprene and saw that it polymerised. Subsequently, chemists at E I DuPont de Nemours and Company made chloroprene by treating vinylacetylene with other substances. DuPont marketed the discovery as Duprene late in 1931.

Modern chemical weapons were first used in a war. German troops released chlorine gas on the front lines at Ypres, Belgium, during the first world war, killing 5000 soldiers.

German chemist Bolander died in a balloon crash. He proposed a valency theory to explain the capacity of an atom to combine with another atom, in light of the newly discovered presence of electrons within the atom.

George Herbert Hitchings born Hoquiam, Washington, US. His father’s death, when George was 12, led him into medicine. He was awarded the Nobel prize in physiology or medicine in 1988 for his discoveries of important principles for drug development. His approach was based on the understanding of basic biochemical and physiological processes.

Arnold Beckman born, Cullom, Illinois, US. He founded Beckman Instruments (now Beckman Coulter) in 1935 with the development of the first Beckman instrument, the pH meter, while he was an assistant professor at the California Institute of Technology.