May - 25 years ago; 90 years ago; 105 years ago; 135 years ago; 195 years ago; 225 years ago

25 years ago 

Norwegian physical chemist Odd Hassel died. He was awarded the Nobel prize for chemistry in 1969, together with Derek Barton, for establishing conformational analysis (the study of a molecule‚Äôs three dimensional geometry). 

90 years ago 

Joseph William Kennedy born in New York, US. Together with Glenn Seaborg and Arthur Wahl, he discovered the radioactive element plutonium.

105 years ago 

US biochemist Conrad Arnold Elvehjem born in Wisconsin. He established that the absence of the vitamin nicotinic acid from diet causes the disease pellagra. 

135 years ago 

Fran?ois Auguste Victor Grignard was born in France. He and Paul Sabatier received the Nobel prize for chemistry in 1912 for developing the Grignard reaction. Grignard reagents have since become important in organic synthesis. 

195 years ago 

John William Draper born in the UK. He was a pioneer in photochemistry, contributing to science through his research in radiant energy.  

225 years ago

French chemist Henri Braconnot was born. He discovered chitin in mushrooms, one of the most abundant polysaccharides in nature. In 1801 he opened the first sugar beet factory in Silesia, (a historical region of Poland, the Czech Republic and Germany).